High-Gain Four-Arm Helical Antenna_Shenzhen Tongxun Precision Technology Co., Ltd.

Overview

The concept of helical antennas can be traced back to the early 20th century, with significant contributions from researchers such as John D. Kraus, who laid the groundwork for understanding the radiation characteristics of single-arm helical structures in the 1940s. Kraus’s work demonstrated that helical antennas could operate in two primary modes: the normal mode (where the helix length is much shorter than the wavelength, resulting in omnidirectional radiation) and the axial mode (where the helix length is comparable to or longer than the wavelength, producing a unidirectional beam along the helix axis). While single-arm helical antennas proved useful in many applications, their limitations—such as relatively low gain, narrow bandwidth, and sensitivity to polarization mismatches—prompted researchers to explore multi-arm configurations. The four-arm helical antenna emerged as a promising solution, leveraging the synergistic effects of multiple arms to enhance performance metrics that are critical for advanced wireless systems.

At its core, a high-gain four-arm helical antenna consists of four identical helical elements (arms) wound around a central dielectric support structure (often referred to as the “boom”). These arms are typically arranged symmetrically around the boom, with equal angular spacing (90 degrees apart) to ensure balanced radiation and polarization characteristics. Each helical arm is a conducting wire or strip that follows a helical path, defined by key parameters such as the helix diameter (D), pitch (p)—the distance advanced along the helix axis per turn—and the number of turns (N). The four arms are usually fed in a way that ensures a 90-degree phase shift between adjacent arms, which is essential for generating circular polarization. This feeding scheme can be implemented using various techniques, such as a quadrature hybrid coupler, a Wilkinson power divider with phase shifters, or a printed circuit board (PCB)-integrated feeding network for miniaturized designs.

One of the defining features of the high-gain four-arm helical antenna is its ability to achieve high directional gain. In the axial mode of operation, which is the most common mode for high-gain applications, the antenna radiates a unidirectional beam along the helix axis, with the gain increasing with the number of turns and the helix diameter (up to a certain limit, beyond which mutual coupling between arms and structural constraints become significant). The four-arm configuration enhances gain compared to single-arm or two-arm helical antennas by increasing the effective aperture of the antenna and reducing radiation losses. Additionally, the symmetric arrangement of the four arms minimizes cross-polarization radiation, ensuring that the majority of the radiated power is concentrated in the desired polarization (either right-hand circular polarization, RHCP, or left-hand circular polarization, LHCP), which is critical for applications such as satellite communication, where polarization matching is essential to avoid signal degradation.

Another key advantage of the high-gain four-arm helical antenna is its broad bandwidth. The bandwidth of a helical antenna is typically defined as the range of frequencies over which the voltage standing wave ratio (VSWR) is less than a specified value (e.g., 2:1) and the polarization purity (axial ratio, AR) remains below a certain threshold (e.g., 3 dB). The four-arm configuration extends the bandwidth by reducing the sensitivity of the antenna to frequency variations. Each arm acts as a separate radiating element, and the mutual coupling between the arms (when properly designed) helps to smooth out the impedance and radiation characteristics across a wider frequency range. This broad bandwidth makes the antenna suitable for multi-band and software-defined radio (SDR) applications, where the ability to operate over multiple frequency bands without significant performance degradation is highly desirable.

The high-gain four-arm helical antenna also exhibits excellent circular polarization performance, which is a critical requirement for many wireless systems. Circular polarization is advantageous because it eliminates the need for precise alignment between the transmitting and receiving antennas (unlike linear polarization, which is highly sensitive to antenna orientation), reduces the effects of multipath fading (a common issue in urban and indoor environments, where signals reflect off buildings, walls, and other objects), and mitigates the impact of Faraday rotation (a phenomenon in which the polarization plane of electromagnetic waves propagating through a magnetized medium, such as the Earth’s ionosphere, rotates). The four-arm configuration ensures that the antenna generates a pure circular polarization by providing a balanced 90-degree phase shift between adjacent arms. This results in a low axial ratio (typically less than 3 dB over the operating bandwidth), which indicates that the polarization is nearly ideal circular.

To understand the role of the high-gain four-arm helical antenna in modern technology, it is important to consider the evolving needs of wireless systems. With the rapid growth of 5G and beyond (6G) communication networks, there is an increasing demand for antennas that can support high data rates, low latency, and reliable connectivity over long distances. In satellite communication, where signals must travel through the Earth’s atmosphere and ionosphere, high gain is essential to compensate for path losses, and circular polarization is necessary to counteract Faraday rotation. In global navigation satellite systems (GNSS), such as GPS, Galileo, and BeiDou, high-gain four-arm helical antennas are used in ground stations and user terminals to improve the accuracy and reliability of positioning, navigation, and timing (PNT) services. In remote sensing applications, such as synthetic aperture radar (SAR) and weather radar, the antenna’s high gain and broad bandwidth enable high-resolution imaging and real-time data acquisition.

Despite its many advantages, the high-gain four-arm helical antenna is not without its challenges. One of the primary challenges is its size and weight, particularly for applications that require high gain (which often necessitates a large number of turns and a large helix diameter). This can make the antenna unsuitable for compact devices, such as portable satellite terminals or small unmanned aerial vehicles (UAVs). Another challenge is the complexity of the feeding network, which must provide a precise 90-degree phase shift between adjacent arms to ensure proper circular polarization. Any deviation from this phase shift can degrade the axial ratio and increase cross-polarization radiation, leading to reduced performance. Additionally, mutual coupling between the four arms can affect the antenna’s impedance and radiation characteristics, especially at higher frequencies, where the spacing between arms becomes a significant fraction of the wavelength. Mitigating mutual coupling requires careful design of the helix parameters, the feeding network, and the dielectric support structure.

In summary, the high-gain four-arm helical antenna is a critical component in modern wireless systems, offering a unique combination of high gain, broad bandwidth, and excellent circular polarization performance. Its historical development, from the early single-arm helical antennas to the advanced four-arm configurations of today, reflects the ongoing efforts to address the evolving needs of communication, navigation, and remote sensing applications. By understanding its key structural components, operational modes, and performance characteristics, engineers and researchers can continue to optimize the design of this antenna type, overcoming existing challenges and unlocking new opportunities for its use in emerging technologies. The following sections will delve deeper into the design and construction, working principles, advantages and challenges, applications and future trends, and conclusion of the high-gain four-arm helical antenna, providing a comprehensive and technical analysis of this important electromagnetic device.

Design and Construction

The design and construction of a high-gain four-arm helical antenna is a multi-faceted process that requires careful consideration of various parameters, materials, and fabrication techniques to ensure optimal performance. Unlike simple antennas, such as dipole or patch antennas, the four-arm helical antenna’s performance is highly sensitive to its geometric dimensions, feeding network design, and material properties. This section will provide a detailed overview of the key design parameters, material selection criteria, feeding network design, fabrication processes, and performance optimization techniques involved in creating a high-gain four-arm helical antenna.

Key Design Parameters

The performance of a high-gain four-arm helical antenna is primarily determined by a set of critical geometric and electrical parameters. These parameters must be carefully chosen to achieve the desired gain, bandwidth, axial ratio, and impedance matching. The most important design parameters include the helix diameter (D), pitch (p), number of turns (N), arm length (L), arm spacing (s), and the diameter of the central dielectric boom (d).

Helix Diameter (D)

The helix diameter (D) is the distance across the helix perpendicular to its axis. It plays a crucial role in determining the antenna’s gain, bandwidth, and operating frequency. In the axial mode of operation (the primary mode for high-gain applications), the optimal helix diameter is typically in the range of 0.2λ to 0.5λ, where λ is the wavelength at the center frequency of operation. A larger diameter increases the effective aperture of the antenna, which in turn increases the gain. However, beyond a certain diameter (approximately 0.5λ), the antenna may start to operate in the conical mode, where the radiation pattern becomes conical rather than unidirectional, leading to a significant reduction in gain. Additionally, a larger diameter increases the size and weight of the antenna, which can be a constraint for compact applications.

Pitch (p)

The pitch (p) is the distance advanced along the helix axis per turn. It is a critical parameter that affects the antenna’s polarization, gain, and impedance. The pitch angle (α), which is the angle between the helical arm and the helix axis, is related to the pitch and diameter by the formula tan(α) = p/(πD). For axial mode operation, the optimal pitch angle is typically between 12 degrees and 15 degrees. This range ensures that the antenna generates a pure circular polarization with a low axial ratio. A smaller pitch angle (less than 12 degrees) can result in linear polarization tendencies, while a larger pitch angle (greater than 15 degrees) can lead to increased cross-polarization radiation and a degradation in gain. The pitch also affects the antenna’s impedance; increasing the pitch generally increases the input impedance, which must be matched to the feeding network to minimize reflection losses.

Number of Turns (N)

The number of turns (N) is another key parameter that directly influences the antenna’s gain. In the axial mode, the gain (G) of a helical antenna is approximately proportional to the number of turns, the helix diameter, and the pitch, according to the formula G ≈ 15(NpD)/λ² (in dBi). This formula shows that increasing the number of turns increases the gain, provided that the other parameters (D and p) are kept within their optimal ranges. However, there is a practical limit to the number of turns, as adding more turns increases the overall length of the antenna (L = Np) and can lead to increased weight, structural instability, and higher ohmic losses (especially at higher frequencies, where the skin effect becomes more significant). Additionally, beyond a certain number of turns, the mutual coupling between adjacent turns (intra-arm coupling) can degrade the antenna’s radiation pattern, leading to side lobe levels (SLL) and a reduction in gain.

Arm Length (L)

The arm length (L) is the total length of each helical arm, which is equal to N times the length of one turn (the circumference of the helix, which is πD, divided by the cosine of the pitch angle α). The arm length is an important parameter for impedance matching, as the input impedance of the antenna is strongly dependent on the length of the radiating elements. For axial mode operation, the arm length is typically in the range of 1λ to 5λ, with longer arms generally providing higher gain but also increasing the antenna’s size and weight.

Arm Spacing (s)

The arm spacing (s) is the angular distance between adjacent helical arms, which is 90 degrees for a four-arm configuration (since 360 degrees / 4 arms = 90 degrees). This symmetric spacing is essential for ensuring balanced radiation and polarization characteristics. Any deviation from 90 degrees (due to manufacturing errors or structural imperfections) can lead to an imbalance in the phase shifts between the arms, resulting in a higher axial ratio and increased cross-polarization radiation. Additionally, the physical spacing between the arms (in terms of linear distance) affects mutual coupling between the arms. A larger physical spacing (which corresponds to a larger helix diameter for a fixed number of arms) reduces mutual coupling, but it also increases the antenna’s size. Conversely, a smaller physical spacing increases mutual coupling, which can degrade the antenna’s impedance and radiation performance.

Central Dielectric Boom Diameter (d)

The central dielectric boom is a non-conducting structure that supports the four helical arms. Its diameter (d) affects the antenna’s weight, structural stability, and dielectric loading. A larger boom diameter provides greater structural support, which is important for antennas with a large number of turns or a large diameter. However, a larger boom also increases the dielectric loading on the antenna, which can shift the operating frequency and affect the impedance. The material of the boom (discussed in the next section) also plays a role in dielectric loading, with materials having a higher relative permittivity (εr) causing a more significant shift in the operating frequency.

Material Selection

The selection of materials for the high-gain four-arm helical antenna is critical for ensuring optimal performance, structural integrity, and cost-effectiveness. The main components of the antenna that require material selection are the helical arms (conducting elements), the central dielectric boom (support structure), and the feeding network (which includes conductors, insulators, and connectors).

Helical Arms (Conducting Elements)

The helical arms are typically made of a highly conductive material to minimize ohmic losses, which can reduce the antenna’s efficiency and gain. The most common materials used for the arms include copper, aluminum, and silver-plated copper. Copper is preferred for its high electrical conductivity (58 S/m at 20°C) and good mechanical strength, but it is relatively heavy and expensive. Aluminum has a lower conductivity (37 S/m at 20°C) than copper but is lighter and more cost-effective, making it suitable for applications where weight is a critical factor (e.g., UAVs or satellite payloads). Silver-plated copper combines the high conductivity of silver (63 S/m at 20°C) with the mechanical strength of copper, providing excellent electrical performance with minimal weight penalty. However, silver plating increases the cost of the antenna, so it is typically used in high-performance applications where maximum efficiency is required (e.g., precision navigation or deep-space communication).

The form of the helical arms can also vary, depending on the application. For low-frequency applications (e.g., VHF or UHF bands), the arms are often made of solid copper or aluminum wire, which is easy to bend into a helical shape. For higher-frequency applications (e.g., microwave or millimeter-wave bands), the arms are typically fabricated as printed strips on a dielectric substrate (such as PCB material) or as thin-walled tubes, which reduce weight and improve the precision of the helical geometry.

Central Dielectric Boom

The central dielectric boom must be made of a material that is lightweight, rigid, and has a low relative permittivity (εr) to minimize dielectric loading on the antenna. The relative permittivity of the boom material affects the antenna’s operating frequency; a higher εr causes the wavelength in the dielectric to be shorter, which can shift the antenna’s resonant frequency to a lower value. To avoid significant frequency shifts, the boom material should have an εr close to 1 (the permittivity of free space). Common materials used for the boom include fiberglass-reinforced plastic (FRP), polytetrafluoroethylene (PTFE, also known as Teflon), and polyethylene. FRP is a popular choice due to its high mechanical strength, low weight, and low εr (typically around 1.5 to 2.0). PTFE has an even lower εr (around 2.1) and excellent chemical resistance, making it suitable for harsh environments (e.g., marine or aerospace applications). Polyethylene has a low εr (around 2.3) and is very lightweight, but it has lower mechanical strength than FRP or PTFE, so it is typically used for small, low-weight antennas.

Feeding Network

The feeding network of the high-gain four-arm helical antenna is responsible for distributing the RF signal to the four arms with a precise 90-degree phase shift between adjacent arms. The materials used in the feeding network must have high conductivity (for conductors) and low dielectric loss (for insulators) to minimize signal loss and phase errors. The conductors in the feeding network are typically made of copper (either solid or printed on a PCB) due to its high conductivity. The insulators (used to separate the conductors and support the feeding network) are often made of PTFE, FR4 (a common PCB material with an εr of around 4.4), or Rogers materials (high-performance PCB materials with low dielectric loss and stable εr over temperature, suitable for high-frequency applications). Connectors (used to interface the feeding network to the RF source or receiver) are typically made of brass or stainless steel with gold plating to ensure low contact resistance and corrosion resistance.

Feeding Network Design

The feeding network is a critical component of the high-gain four-arm helical antenna, as it directly affects the antenna’s polarization performance, impedance matching, and overall efficiency. The primary goal of the feeding network is to provide each of the four arms with a signal that is equal in amplitude and has a 90-degree phase shift relative to the adjacent arms. This ensures that the antenna generates a pure circular polarization. There are several common feeding network topologies used for four-arm helical antennas, including the quadrature hybrid coupler, the Wilkinson power divider with phase shifters, and the PCB-integrated feeding network.

Quadrature Hybrid Coupler

The quadrature hybrid coupler (also known as a 90-degree hybrid coupler) is a passive RF component that splits an input signal into two output signals with a 90-degree phase shift. To feedthe four-arm helical antenna, two quadrature hybrid couplers are typically used in a cascaded configuration. The first coupler splits the input signal into two signals with a 90° phase shift (e.g., 0° and 90°). Each of these two signals is then fed into a second quadrature hybrid coupler, which further splits them into two more signals, each with an additional 90° phase shift. This results in four output signals with phase shifts of 0°, 90°, 180°, and 270°—exactly the phase relationship required for the four arms of the helical antenna.

Quadrature hybrid couplers offer several advantages for this application. They provide excellent amplitude balance (typically within ±0.5 dB) and phase accuracy (within ±5°) across the operating bandwidth, ensuring that the four arms receive signals with nearly equal amplitude and precise phase shifts. They also have high isolation between the output ports (typically greater than 20 dB), which minimizes crosstalk between the arms and reduces interference. However, quadrature hybrid couplers can be relatively large and bulky, especially at lower frequencies (e.g., UHF or VHF bands), which can be a constraint for compact antenna designs. Additionally, they are typically designed for a specific impedance (e.g., 50 Ω), so impedance matching between the coupler and the helical arms is essential to minimize reflection losses.

Wilkinson Power Divider with Phase Shifters

Another common feeding network topology is the Wilkinson power divider combined with phase shifters. The Wilkinson power divider is a passive component that splits an input signal into multiple output signals with equal amplitude and in-phase (0° phase shift) relationship. For a four-arm helical antenna, a two-stage Wilkinson divider is used: the first stage splits the input into two equal signals, and the second stage splits each of those into two more signals, resulting in four equal-amplitude, in-phase signals. To achieve the required 90° phase shift between adjacent arms, phase shifters are inserted into the signal paths of three of the four output ports. For example, a 90° phase shifter is added to the second arm, a 180° phase shifter to the third arm, and a 270° phase shifter to the fourth arm, resulting in phase shifts of 0°, 90°, 180°, and 270° for the four arms.

The Wilkinson power divider with phase shifters offers flexibility in terms of design and integration. Wilkinson dividers can be easily fabricated on PCBs, making them suitable for miniaturized antenna designs. They also provide good amplitude balance (within ±1 dB) and high isolation between output ports (greater than 20 dB). However, the addition of phase shifters introduces complexity and potential phase errors. The phase shifters must be designed to provide precise phase shifts across the operating bandwidth, and any deviation from the desired phase shift (due to frequency variations or manufacturing tolerances) can degrade the antenna’s axial ratio. Additionally, phase shifters can introduce insertion loss (typically 0.5–1 dB per phase shifter), which reduces the overall efficiency of the antenna.

PCB-Integrated Feeding Network

For miniaturized and low-profile high-gain four-arm helical antennas (e.g., those used in portable devices or UAVs), a PCB-integrated feeding network is often the preferred choice. This topology integrates the power division and phase shifting functions directly onto a PCB, eliminating the need for discrete components (such as separate couplers or phase shifters) and reducing the size, weight, and cost of the antenna.

The PCB-integrated feeding network typically uses microstrip or stripline transmission lines to implement the power division and phase shifting. Microstrip lines are preferred for low-cost, easy-to-fabricate designs, while stripline lines are used for higher-frequency applications (e.g., microwave bands) where better shielding and lower radiation losses are required. The power division is achieved using a series of T-junctions or Wilkinson divider sections, and the phase shifting is implemented by varying the length of the transmission lines (since the phase of a signal propagating along a transmission line is proportional to the line length). For example, to achieve a 90° phase shift between two adjacent arms, the transmission line feeding one arm is made λ/4 longer than the line feeding the other arm (since a λ/4 length corresponds to a 90° phase shift at the center frequency).

The PCB-integrated feeding network offers several key advantages. It is highly compact, lightweight, and cost-effective, making it suitable for mass-produced applications. It also provides good integration with the helical arms, which can be fabricated as printed strips on the same PCB (for high-frequency designs). However, this topology is more sensitive to manufacturing tolerances (e.g., variations in line width or substrate thickness), which can affect the amplitude balance and phase accuracy. Additionally, microstrip lines have higher radiation losses than discrete components, especially at higher frequencies, which can reduce the antenna’s efficiency.

Fabrication Processes

The fabrication of a high-gain four-arm helical antenna involves several steps, from the manufacturing of individual components (helical arms, central boom, feeding network) to the final assembly and testing. The specific fabrication processes depend on the antenna’s design, operating frequency, and application requirements (e.g., size, weight, environmental robustness).

Fabrication of Helical Arms

The fabrication of the helical arms varies depending on the material and form of the arms (wire, tube, or printed strip).

For wire-based arms (used in low-frequency applications), the process typically involves the following steps:

Material Cutting: A solid copper or aluminum wire is cut to the required length (calculated based on the number of turns, helix diameter, and pitch).

Helical Forming: The wire is wound around a mandrel (a cylindrical tool with a diameter equal to the desired helix diameter) to form the helical shape. The mandrel is marked at intervals corresponding to the pitch to ensure uniform winding. After winding, the wire is heat-treated (if necessary) to retain the helical shape.

Trimming and Finishing: The ends of the wire are trimmed to the correct length, and any sharp edges are smoothed to prevent damage to the feeding network or dielectric boom. For silver-plated copper arms, the wire is plated with a thin layer of silver using an electroplating process to improve conductivity.

For tube-based arms (used in medium-frequency applications), the process is similar to wire-based arms, but thin-walled copper or aluminum tubes are used instead of solid wire. The tubes are lighter than solid wire, making them suitable for weight-sensitive applications. The forming process requires careful control to avoid collapsing the tube, and the mandrel may have a smaller diameter to account for the tube’s wall thickness.

For printed strip arms (used in high-frequency applications), the fabrication is integrated with the PCB manufacturing process:

Substrate Preparation: A dielectric substrate (e.g., FR4, Rogers) is cut to the required size.

Metallization: A thin layer of copper (typically 17–35 μm thick) is deposited on one or both sides of the substrate using a process such as electroplating or sputtering.

Patterning: The copper layer is patterned using photolithography to create the helical strip shape. This involves applying a photoresist layer to the copper, exposing it to UV light through a mask (with the helical pattern), developing the photoresist, and etching away the unwanted copper.

Finishing: The PCB is cleaned to remove any residual photoresist or etchant, and the edges are trimmed to the final size.

Fabrication of Central Dielectric Boom

The central dielectric boom is typically fabricated using extrusion, molding, or machining processes, depending on the material and desired shape.

For FRP booms:

Fiber Impregnation: Glass fibers are impregnated with a thermosetting resin (e.g., epoxy).

Extrusion or Pultrusion: The impregnated fibers are pulled through a die (pultrusion) or pushed through a die (extrusion) to form a cylindrical shape. The die is heated to cure the resin, resulting in a rigid, lightweight boom.

Cutting and Finishing: The boom is cut to the required length, and the ends are sanded to ensure a smooth surface for attaching the helical arms.

For PTFE or polyethylene booms:

Molding: The material is heated to a molten state and injected into a cylindrical mold. After cooling, the mold is opened, and the boom is removed.

Machining: For complex shapes or precise dimensions, the molded boom may be machined using a lathe or milling machine to achieve the desired diameter and surface finish.

Assembly of the Antenna

The assembly process involves integrating the helical arms, central boom, and feeding network into a single unit:

Attaching Helical Arms to Boom: The helical arms are attached to the central boom using a non-conductive adhesive (e.g., epoxy) or mechanical fasteners (e.g., plastic clips). For wire or tube arms, the adhesive is applied to the points where the arms contact the boom, ensuring that the arms are aligned symmetrically (90° apart) and securely fastened. For printed strip arms, the PCB with the helical strips is attached to the boom using adhesive, with the strips oriented to form the four-arm configuration.

Connecting Feeding Network to Arms: The output ports of the feeding network are connected to the ends of the helical arms using soldering (for wire/tube arms) or conductive adhesive (for printed strip arms). Care is taken to ensure that the connections are secure and that the phase shifts between the arms are maintained. For PCB-integrated feeding networks, the connections are already part of the PCB design, so no additional soldering is required.

Enclosure and Protection (Optional): For antennas used in harsh environments (e.g., outdoor or aerospace applications), an enclosure made of a lightweight, weather-resistant material (e.g., plastic, aluminum) is added to protect the antenna from moisture, dust, and physical damage. The enclosure is designed to be transparent to RF signals (i.e., it has a low dielectric loss and does not block the radiation pattern).

Performance Optimization Techniques

After fabrication, the performance of the high-gain four-arm helical antenna is tested and optimized to ensure that it meets the desired specifications. Common performance metrics include gain, bandwidth, axial ratio, VSWR, and radiation pattern. The following are key optimization techniques used to improve these metrics:

Impedance Matching Optimization

Impedance matching is critical for minimizing reflection losses and maximizing the power transfer between the feeding network and the helical arms. If the VSWR is higher than the specified threshold (e.g., 2:1), several optimization techniques can be used:

Adjusting Arm Length: The length of the helical arms is adjusted by trimming small sections (typically λ/16 or λ/32) from the ends. Shortening the arms increases the input impedance, while lengthening them decreases it.

Adding Matching Networks: A matching network (e.g., a λ/4 transformer, a shunt capacitor, or a series inductor) is added between the feeding network and the helical arms. The matching network is designed to transform the impedance of the arms to match the impedance of the feeding network (e.g., 50 Ω). For PCB-integrated designs, the matching network can be implemented as additional microstrip lines on the PCB.

Modifying Helix Parameters: The helix diameter or pitch is slightly adjusted to change the input impedance. For example, increasing the diameter decreases the impedance, while increasing the pitch increases it. However, these adjustments must be done carefully to avoid degrading other performance metrics (e.g., gain or axial ratio).

Axial Ratio Optimization

A high axial ratio (greater than 3 dB) indicates poor circular polarization performance. To optimize the axial ratio, the following techniques are used:

Adjusting Phase Shifts: The phase shifters in the feeding network are calibrated to ensure that the phase shift between adjacent arms is exactly 90°. This can be done by measuring the phase of each arm’s signal using a vector network analyzer (VNA) and adjusting the phase shifters (e.g., by trimming the length of microstrip lines in a PCB-integrated network) to correct any deviations.

Balancing Amplitude: The amplitude of the signals fed to each arm is measured using a VNA, and any imbalances are corrected by adjusting the power divider (e.g., by changing the resistance values in a Wilkinson divider or the line widths in a microstrip divider).

Improving Arm Symmetry: The helical arms are inspected for symmetry (e.g., equal length, uniform pitch, symmetric spacing). Any structural imperfections (e.g., a bent arm or uneven spacing) are corrected by repositioning or reshaping the arms.

Gain and Radiation Pattern Optimization

To maximize the gain and improve the radiation pattern (e.g., reduce side lobe levels), the following techniques are used:

Optimizing Number of Turns: The number of turns is adjusted to find the optimal balance between gain and size. Adding more turns increases gain, but beyond a certain point, the gain improvement diminishes due to intra-arm coupling. The radiation pattern is measured using an anechoic chamber, and the number of turns is adjusted until the desired gain and side lobe levels are achieved.

Reducing Ohmic Losses: The conductivity of the helical arms is improved by using a more conductive material (e.g., switching from aluminum to copper) or by adding a conductive coating (e.g., silver plating). The feeding network’s conductors are also optimized to reduce losses (e.g., using thicker copper lines or low-loss dielectric materials).

Minimizing Mutual Coupling: The spacing between the helical arms is adjusted to reduce mutual coupling. For example, increasing the spacing decreases coupling but increases the antenna’s size. Alternatively, a dielectric spacer (made of a low-εr material) is added between the arms to reduce coupling without increasing the size significantly.

Working Principles

To fully understand the functionality of a high-gain four-arm helical antenna, it is essential to explore its underlying working principles, including the generation of electromagnetic radiation, the mechanisms of circular polarization, the axial mode of operation (the primary mode for high-gain applications), and the role of mutual coupling and impedance matching. These principles govern how the antenna converts electrical energy into electromagnetic waves (for transmission) or vice versa (for reception) and how it achieves its key performance characteristics, such as high gain, broad bandwidth, and excellent circular polarization.

Electromagnetic Radiation from Helical Arms

At its core, the high-gain four-arm helical antenna operates based on the fundamental principle of electromagnetic radiation from accelerating electric charges. When an RF signal is fed to the helical arms, it creates an alternating current (AC) that flows along the length of the arms. As the current alternates, it accelerates the electric charges in the conductors, which in turn generates time-varying electric and magnetic fields. These fields propagate away from the antenna as electromagnetic waves, carrying the RF signal energy through space.

The radiation from a helical arm is similar to that from a dipole antenna but with a twist—literally. A dipole antenna consists of two straight conductors, and its radiation pattern is omnidirectional in the plane perpendicular to the dipole axis. A helical arm, by contrast, is a curved conductor that follows a helical path. The curvature of the arm causes the current to have both axial (along the helix axis) and circumferential (around the helix) components. These components interact to produce a radiation pattern that is highly directional along the helix axis, especially in the axial mode of operation.

To visualize this, consider a single helical arm. As the AC current flows along the arm, each small segment of the arm acts as a tiny dipole, radiating electromagnetic waves. The radiation from these segments interferes constructively in the direction along the helix axis and destructively in other directions, resulting in a unidirectional beam. For a four-arm helical antenna, the radiation from the four arms adds up constructively in the axial direction, further enhancing the gain and directionality of the beam.

The frequency of the electromagnetic waves radiated by the antenna is determined by the frequency of the AC current (i.e., the frequency of the RF signal fed to the arms). The wavelength (λ) of the waves is related to the frequency (f) by the formula λ = c/f, where c is the speed of light in free space (approximately 3×10⁸ m/s). The dimensions of the helical arms (e.g., length, diameter, pitch) are designed to be compatible with the wavelength of the operating frequency, ensuring that the antenna resonates and radiates efficiently.

Generation of Circular Polarization

One of the most important working principles of the high-gain four-arm helical antenna is its ability to generate circular polarization. Circular polarization differs from linear polarization (where the electric field oscillates in a single plane) in that the electric field of a circularly polarized wave rotates as it propagates through space. This rotation can be either clockwise (right-hand circular polarization, RHCP) or counterclockwise (left-hand circular polarization, LHCP), depending on the direction of the phase shift between the antenna’s arms.

The four-arm helical antenna generates circular polarization through the combination of two key factors: the symmetric arrangement of the four arms (90° apart) and the precise 90° phase shift between the RF signals fed to adjacent arms. Here’s a detailed breakdown of how this works:

Phase Shifted Signals: The feeding network supplies each of the four arms with an RF signal of equal amplitude but with a phase shift of 0°, 90°, 180°, and 270° (for RHCP) or 0°, -90°, -180°, and -270° (for LHCP). For example, if the first arm receives a signal with a phase of 0°, the second arm receives a signal with a phase of 90°, the third arm 180°, and the fourth arm 270°.

Electric Field Components: Each arm radiates an electromagnetic wave with an electric field that has two components: a radial component (perpendicular to the helix axis) and an azimuthal component (tangential to the helix circumference). These components are perpendicular to each other and to the direction of wave propagation (which is along the helix axis, following the right-hand rule for electromagnetic waves).

Constructive Interference of Components: Due to the 90° phase shift between adjacent arms, the radial and azimuthal electric field components from each arm reach their maximum and minimum values at different times. For example, when the radial component of the 0° arm is at its peak, the azimuthal component of the 90° arm is also at its peak. As the waves propagate along the helix axis, these perpendicular components combine and interfere constructively. The result is a single electric field that rotates continuously as it moves through space—this is the circularly polarized wave.

To illustrate this, imagine observing the electric field of the wave from the direction of propagation (along the helix axis). For RHCP, the field would appear to rotate clockwise; for LHCP, it would rotate counterclockwise. The rate of rotation is equal to the frequency of the RF signal—higher frequencies result in faster rotation.

The purity of the circular polarization (measured by the axial ratio, AR) depends on the precision of the phase shifts and amplitude balance between the four arms. If the phase shift deviates from 90° or the amplitude of the signals is unbalanced, the electric field will not rotate uniformly. Instead, it will trace an elliptical path (elliptical polarization), which increases the axial ratio. A low axial ratio (typically <3 dB) indicates nearly ideal circular polarization, which is critical for applications like satellite communication, where polarization mismatches can lead to significant signal loss.

Axial Mode of Operation: The Key to High Gain

The high-gain four-arm helical antenna primarily operates in the axial mode—the only mode that delivers the unidirectional, high-gain radiation pattern required for long-range and high-data-rate applications. Unlike the normal mode (where the helix length is much shorter than λ, resulting in omnidirectional radiation with low gain) or the conical mode (where the helix diameter exceeds 0.5λ, leading to a conical radiation pattern and reduced gain), the axial mode is optimized for directional performance.

Conditions for Axial Mode Operation

For an antenna to operate in the axial mode, its geometric parameters must satisfy specific criteria relative to the wavelength (λ) of the operating frequency:

Helix Diameter (D): 0.2λ ≤ D ≤ 0.5λ. This range ensures that the electromagnetic waves radiated from adjacent turns of the helix interfere constructively along the axis. If D < 0.2λ, the antenna tends to operate in the normal mode; if D > 0.5λ, it shifts to the conical mode.

Pitch Angle (α): 12° ≤ α ≤ 15°. The pitch angle (defined as tan⁻¹(p/(πD)), where p is the pitch) controls the balance between the axial and circumferential current components. This range ensures that the current distribution along the helix is uniform, maximizing constructive interference in the axial direction.

Number of Turns (N): Typically 3 ≤ N ≤ 15. While more turns increase gain (as each turn contributes to the radiated field), beyond 15 turns, the gain improvement plateaus due to intra-arm coupling (interference between adjacent turns of the same arm) and increased ohmic losses.

Radiation Pattern in Axial Mode

In the axial mode, the high-gain four-arm helical antenna produces a unidirectional radiation pattern with a narrow main lobe along the helix axis and low side lobe levels (SLL). The main lobe carries the majority of the radiated power (typically >90%), while the side lobes (weaker beams in non-axial directions) are minimized to reduce interference with other systems.

The shape of the radiation pattern is influenced by the number of turns (N) and helix diameter (D):

Beamwidth: The half-power beamwidth (HPBW)—the angle over which the power of the main lobe is at least half of its maximum value—decreases as N and D increase. A smaller HPBW indicates a more focused beam and higher gain. For example, an antenna with N=8 and D=0.4λ might have an HPBW of ~20°, while one with N=12 and D=0.5λ could have an HPBW of ~15°.

Side Lobe Levels (SLL): SLL is typically between -15 dB and -25 dB in well-designed axial mode antennas. Lower SLL is achieved by ensuring uniform current distribution along the helical arms and minimizing mutual coupling between arms. Techniques like tapering the width of the helical strips (for printed designs) or adjusting the pitch of the outer turns can further reduce SLL.

Gain Calculation in Axial Mode

The gain (G) of a four-arm helical antenna in the axial mode is a function of its effective aperture (the area over which it captures or radiates electromagnetic energy) and efficiency (the ratio of radiated power to input power). A simplified formula for calculating the gain (in dBi, relative to an isotropic radiator) is:

**\( G = 15 \times \frac{N \times p \times D}{\lambda^2} \times \eta \)

Where:

\( N \): Number of turns

\( p \): Pitch (distance per turn along the axis)

\( D \): Helix diameter

\( \lambda \): Wavelength at the operating frequency

\( \eta \): Antenna efficiency (typically 0.7–0.9 for well-designed antennas, accounting for ohmic losses, dielectric losses, and reflection losses)

For example, a four-arm helical antenna with \( N=10 \), \( p=0.2\lambda \), \( D=0.4\lambda \), and \( \eta=0.8 \) would have a gain of:

**\( G = 15 \times \frac{10 \times 0.2\lambda \times 0.4\lambda}{\lambda^2} \times 0.8 = 15 \times 0.8 \times 0.8 = 9.6 \, \text{dBi} \)

In practice, gains of 10–20 dBi are common for high-gain four-arm helical antennas, with some designs (e.g., those used in deep-space communication) achieving gains exceeding 25 dBi by increasing the number of turns or integrating the antenna with a reflector (a metallic surface behind the helix that reflects back radiation, effectively doubling the effective aperture).

Role of Mutual Coupling

Mutual coupling—electromagnetic interaction between the four helical arms—plays a dual role in the performance of the high-gain four-arm helical antenna. While excessive mutual coupling can degrade impedance matching, axial ratio, and gain, controlled mutual coupling can enhance bandwidth and polarization purity. Understanding and managing mutual coupling is therefore a critical aspect of the antenna’s working principles.

Causes of Mutual Coupling

Mutual coupling arises because each helical arm acts as both a radiator and a receiver of electromagnetic fields. When one arm radiates a wave, a portion of that wave is intercepted by adjacent arms, inducing an unwanted current (coupled current) in those arms. The strength of mutual coupling depends on several factors:

Arm Spacing: Closer spacing between arms (smaller helix diameter relative to λ) increases coupling, as the electromagnetic fields from one arm are more likely to reach adjacent arms.

Frequency: At higher frequencies (smaller λ), the physical spacing between arms becomes a larger fraction of λ, increasing the coupling coefficient (a measure of coupling strength).

Helix Parameters: A larger number of turns or a smaller pitch angle increases the overlap between the fields of adjacent arms, enhancing coupling.

Effects of Mutual Coupling

Impedance Distortion: The coupled currents alter the input impedance of each arm. For example, if the input impedance of an isolated arm is 50 Ω, mutual coupling might shift it to 40 Ω or 60 Ω, leading to a mismatch with the 50 Ω feeding network. This increases VSWR and reflection losses.

Axial Ratio Degradation: If coupling is uneven between arms (e.g., stronger coupling between Arm 1 and Arm 2 than between Arm 2 and Arm 3), the amplitude and phase of the signals in the arms become unbalanced. This disrupts the uniform rotation of the electric field, increasing the axial ratio.

Gain Reduction: Excessive coupling causes some of the radiated power to be absorbed by adjacent arms (as coupled currents) rather than propagating away from the antenna. This reduces the total radiated power and, consequently, the gain.

Bandwidth Enhancement: In controlled scenarios (e.g., when the coupling coefficient is between 0.1 and 0.3), mutual coupling can smooth out the impedance variations across frequency. This is because the coupled currents act as a “feedback” mechanism, compensating for changes in the arm’s impedance with frequency, thereby extending the bandwidth over which VSWR < 2:1.

Mitigating Excessive Mutual Coupling

To minimize the negative effects of mutual coupling, several design strategies are employed:

Optimal Arm Spacing: The helix diameter is chosen such that the spacing between adjacent arms is ~0.1λ–0.2λ. This balance ensures that coupling is strong enough to enhance bandwidth but weak enough to avoid impedance and axial ratio degradation.

Dielectric Spacers: Low-permittivity (εr < 2.5) dielectric spacers (e.g., PTFE or polyethylene) are placed between the arms. These spacers absorb a portion of the electromagnetic fields, reducing the coupled currents without introducing significant dielectric losses.

Arm Tapering: For printed strip arms, the width of the strips is tapered (gradually reduced) toward the ends of the helix. This reduces the current amplitude at the ends of the arms, where coupling is most intense, thereby lowering the coupling coefficient.

Feeding Network Isolation: The feeding network is designed with high isolation between output ports (e.g., using Wilkinson dividers with isolation resistors or quadrature hybrid couplers with >20 dB port isolation). This prevents coupled currents in the arms from propagating back to the feeding network, where they could cause further interference.

Impedance Matching: Ensuring Efficient Power Transfer

Impedance matching is a fundamental working principle that ensures maximum power transfer between the feeding network and the helical arms. When the input impedance of the antenna (Zant) matches the characteristic impedance of the feeding network (Z0, typically 50 Ω), reflection losses are minimized, and nearly all the input power is radiated as electromagnetic waves. Conversely, a mismatch causes a portion of the power to be reflected back to the source, reducing efficiency and potentially damaging the RF components.

Input Impedance of the Four-Arm Helical Antenna

The input impedance of the high-gain four-arm helical antenna is the parallel combination of the input impedances of the four individual arms, adjusted for mutual coupling. For an isolated single-arm helical antenna in axial mode, the input impedance (Zarm) is typically between 30 Ω and 70 Ω, depending on the helix parameters (D, p, N). For a four-arm configuration, the total input impedance (Zant) is approximately Zarm / 4 (due to the parallel connection of four identical arms), but mutual coupling can shift this value by ±10 Ω.

For example, if each isolated arm has an impedance of 200 Ω, the ideal parallel impedance (without coupling) would be 50 Ω (200 Ω / 4). However, if mutual coupling reduces each arm’s impedance to 180 Ω, the total impedance becomes 45 Ω, creating a mismatch with a 50 Ω feeding network.

Impedance Matching Mechanisms

To achieve Zant = Z0, several matching mechanisms are integrated into the antenna’s design, as briefly introduced in the “Performance Optimization Techniques” section. Here, we explain their underlying working principles:

λ/4 Transformer: A λ/4 transformer is a section of transmission line (e.g., microstrip or coaxial cable) with a characteristic impedance (Zt) of \( \sqrt{Z_{ant} \times Z_0} \). When placed between the feeding network and the antenna, it transforms Zant to Z0 through the principle of impedance transformation in transmission lines. For example, if Zant = 45 Ω and Z0 = 50 Ω, Zt = \( \sqrt{45 \times 50} \approx 47.4 \) Ω. The λ/4 length ensures that the phase of the reflected wave is reversed twice (once at each end of the transformer), causing the reflected waves to cancel out, resulting in a matched condition.

Shunt Capacitors/Series Inductors: These passive components are used to cancel the reactive part of the antenna’s impedance (if Zant has a capacitive or inductive component). For example, if Zant = 45 - j10 Ω (capacitive), a series inductor with a reactance of +j10 Ω is added to cancel the capacitive reactance, resulting in a purely resistive impedance of 45 Ω. A λ/4 transformer can then be used to match 45 Ω to 50 Ω.

Stub Matching: A stub is a short-circuited or open-circuited section of transmission line connected in parallel (shunt stub) or series (series stub) with the main line. By adjusting the length and position of the stub, it is possible to cancel the reactive component of Zant and adjust the resistive component to match Z0. For example, a shunt stub with a length of λ/8 can cancel a capacitive reactance by introducing an inductive reactance of equal magnitude.

Measuring and Maintaining Impedance Matching

The impedance matching of the antenna is measured using a Vector Network Analyzer (VNA), which sends a swept-frequency RF signal to the antenna and measures the reflection coefficient (Γ)—a complex quantity that describes the magnitude and phase of the reflected wave. The VSWR is then calculated from Γ using the formula:

**\( \text{VSWR} = \frac{1 + |\Gamma|}{1 - |\Gamma|} \)

A VSWR of 1:1 indicates a perfect match (no reflection), while a VSWR of 2:1 is the typical maximum acceptable value for most applications (corresponding to ~10% power reflection).

To maintain impedance matching over the operating bandwidth, the matching network is designed to be broadband. For example, a λ/4 transformer made from a low-loss dielectric material (e.g., Rogers RT/duroid 5880) can maintain a VSWR < 2:1 over a 15–20% bandwidth. Additionally, the helical arms are designed with uniform dimensions (e.g., consistent pitch and diameter) to ensure that Zant remains stable across frequency.

Advantages and Challenges

The high-gain four-arm helical antenna has become a staple in modern wireless systems due to its unique combination of performance attributes. However, like all antenna technologies, it faces inherent limitations that must be addressed during design and deployment. This section provides a detailed analysis of the antenna’s key advantages—including high directional gain, excellent circular polarization, broad bandwidth, and environmental robustness—and the critical challenges it presents, such as size constraints, fabrication complexity, mutual coupling issues, and cost considerations. Key Advantages 1. High Directional Gain for Long-Range Communication One of the most significant advantages of the high-gain four-arm helical antenna is its ability to deliver high directional gain in the axial mode. As discussed in the “Working Principles” section, the antenna’s gain is directly proportional to the number of turns (N), helix diameter (D), and pitch (p), making it highly customizable for long-range applications where signal path loss is a major concern. Path Loss Compensation: In satellite communication, for example, signals travel over distances of 35,786 km (for geostationary satellites) or more, resulting in extreme path loss (typically >200 dB). A high-gain antenna (15–25 dBi) can compensate for this loss by focusing the radiated power into a narrow beam, ensuring that the signal reaches the satellite (or ground station) with sufficient strength to be detected. Improved Signal-to-Noise Ratio (SNR): The narrow main lobe of the axial mode radiation pattern minimizes the reception of unwanted noise and interference from off-axis directions. This increases the SNR, which is critical for high-data-rate applications like 6G backhaul or remote sensing, where even small SNR improvements can enhance data throughput and image resolution. Multi-Point Communication: In point-to-point (P2P) or point-to-multipoint (P2MP) communication systems (e.g., microwave links for cellular backhaul), the high directional gain allows the antenna to target specific receivers while avoiding interference with other systems. This is particularly useful in dense urban environments, where multiple wireless systems operate in close proximity. Real-world examples highlight this advantage: the NASA Deep Space Network (DSN) uses large-aperture helical antennas (with gains >30 dBi) to communicate with spacecraft like the Mars rovers, where signals must travel over 55 million km. Similarly, ground-based GNSS reference stations use high-gain four-arm helical antennas to receive weak signals from GPS, Galileo, and BeiDou satellites, enabling centimeter-level positioning accuracy. 2. Excellent Circular Polarization Performance Circular polarization (CP) is a defining feature of the high-gain four-arm helical antenna, and its superior CP performance sets it apart from many other antenna types (e.g., patch antennas, which often have high axial ratios). This advantage is critical for applications where polarization mismatches or environmental effects (like Faraday rotation) can degrade signal quality. Immunity to Polarization Mismatch: Unlike linearly polarized (LP) antennas, which require precise alignment between the transmitting and receiving antennas (a 90° misalignment can result in 100% signal loss), CP antennas are orientation-independent. A RHCP transmitting antenna can communicate with a RHCP receiving antenna regardless of their relative rotation, making themideal for applications where antenna alignment is difficult or dynamic. For example, in UAV-based remote sensing, the UAV’s orientation changes constantly during flight. A CP four-arm helical antenna on the UAV ensures that the communication link with the ground station remains stable, even as the UAV pitches, rolls, or yaws. Mitigation of Faraday Rotation: When electromagnetic waves propagate through the Earth’s ionosphere (a common scenario in satellite communication or GNSS), the ionized particles (electrons and ions) interact with the wave’s electric field, causing the polarization plane to rotate—a phenomenon known as Faraday rotation. For LP antennas, this rotation can lead to significant signal loss (up to 30 dB in extreme cases) as the polarization of the received signal no longer matches the antenna’s polarization. CP antennas, however, are inherently immune to Faraday rotation. Since the electric field of a CP wave is already rotating, the additional rotation from the ionosphere only changes the rate of rotation, not the polarization state (RHCP remains RHCP, LHCP remains LHCP). This ensures consistent signal reception, making CP four-arm helical antennas the preferred choice for satellite and ionospheric communication systems. Reduced Multipath Fading: Multipath fading occurs when a signal reaches the receiver via multiple paths (e.g., direct line-of-sight, reflections off buildings or terrain), leading to constructive or destructive interference. For LP antennas, reflections can change the polarization of the signal (e.g., a vertically polarized signal may become horizontally polarized after reflection), resulting in deep fades (signal loss of 20–40 dB). CP signals, by contrast, retain their polarization state after reflection (RHCP remains RHCP), so the direct and reflected signals have the same polarization and interfere less destructively. This reduces the severity of multipath fading, improving link reliability in urban, indoor, or maritime environments. 3. Broad Bandwidth for Multi-Band Applications The high-gain four-arm helical antenna exhibits a broad operating bandwidth, defined as the frequency range over which key performance metrics (VSWR < 2:1, axial ratio < 3 dB, gain variation < 3 dB) are maintained. This bandwidth advantage stems from the antenna’s unique helical structure and the synergistic effects of the four-arm configuration. Bandwidth Determinants: The bandwidth of a helical antenna is primarily influenced by the helix diameter (D), pitch (p), and the design of the feeding network. For axial mode operation, the relative bandwidth (bandwidth divided by center frequency) typically ranges from 15% to 30%, which is significantly broader than that of many other high-gain antennas (e.g., patch antennas, which have relative bandwidths of 5–10%). The four-arm configuration extends this bandwidth further by reducing the sensitivity of the antenna’s impedance and polarization characteristics to frequency variations. Each arm acts as a separate radiating element, and controlled mutual coupling between the arms smooths out impedance fluctuations across frequency. Multi-Band Compatibility: The broad bandwidth makes the antenna suitable for multi-band applications, where a single antenna must operate over multiple frequency bands. For example, in 5G communication, the antenna may need to support both the sub-6 GHz band (3.5 GHz) and the mmWave band (28 GHz). A well-designed four-arm helical antenna can be optimized to cover these bands with minimal performance degradation. Similarly, in GNSS systems, the antenna must receive signals from multiple constellations (GPS L1: 1575.42 MHz, Galileo E1: 1575.42 MHz, BeiDou B1: 1561.098 MHz), and the broad bandwidth ensures that all these frequencies are within the antenna’s operating range. Software-Defined Radio (SDR) Integration: SDR systems require antennas with broad bandwidths to support dynamic frequency hopping and reconfigurable operation. The high-gain four-arm helical antenna’s ability to operate over a wide frequency range makes it an ideal choice for SDR applications, such as military communication systems or cognitive radio networks, where the antenna must adapt to changing spectral environments. 4. Environmental Robustness for Harsh Operating Conditions The high-gain four-arm helical antenna is inherently robust to environmental factors, such as temperature variations, moisture, vibration, and electromagnetic interference (EMI). This robustness makes it suitable for deployment in harsh environments, including aerospace, maritime, and industrial settings. Temperature Stability: The materials used in the antenna’s construction—such as copper or silver-plated copper for the arms, FRP or PTFE for the central boom, and low-loss dielectrics for the feeding network—exhibit stable electrical and mechanical properties over a wide temperature range (-55°C to +125°C for aerospace-grade materials). This ensures that the antenna’s performance (gain, axial ratio, impedance) remains consistent, even in extreme temperature conditions (e.g., the cold of space or the heat of a desert). Moisture and Corrosion Resistance: The helical arms can be coated with corrosion-resistant materials (e.g., gold plating or chromate conversion coatings) to protect against moisture and saltwater corrosion—critical for maritime applications (e.g., ship-borne satellite terminals) or outdoor deployments. The central boom, made of FRP or PTFE, is non-absorbent and resistant to water damage, further enhancing the antenna’s durability in wet environments. Vibration and Shock Resistance: The rigid structure of the antenna—with the helical arms securely attached to the central boom—enables it to withstand high levels of vibration and shock. This is essential for aerospace applications (e.g., antennas mounted on aircraft or rockets) or industrial settings (e.g., antennas used in heavy machinery), where vibrations can damage less robust antenna designs. EMI Immunity: The symmetric four-arm configuration and the narrow radiation pattern of the antenna minimize the reception of EMI from external sources (e.g., power lines, industrial equipment). Additionally, the feeding network can be shielded with metallic enclosures to further reduce EMI, ensuring that the antenna operates reliably in electromagnetically noisy environments. Critical Challenges 1. Size and Weight Constraints for Compact Applications One of the most significant challenges of the high-gain four-arm helical antenna is its size and weight, which are directly related to its gain. To achieve high gain, the antenna requires a large number of turns (N) and a large helix diameter (D)—both of which increase the antenna’s overall length (L = N × p) and weight. This makes the antenna unsuitable for compact applications, such as portable devices, small UAVs, or wearable technology. Size-Gain Tradeoff: The gain of the antenna increases with the number of turns and helix diameter, but this comes at the cost of size. For example, a four-arm helical antenna with a gain of 20 dBi (suitable for satellite communication) operating at 1.5 GHz (λ ≈ 20 cm) would require D ≈ 0.4λ = 8 cm, p ≈ 0.2λ = 4 cm, and N ≈ 15 turns. This results in an overall length of L = 15 × 4 cm = 60 cm and a diameter of 8 cm—far too large for a portable satellite terminal (which typically requires an antenna diameter of <10 cm and length of <20 cm). Weight Implications: The materials used for high-gain designs (e.g., solid copper arms, thick FRP booms) add significant weight. For example, the 20 dBi antenna described above would weigh approximately 1–2 kg, which is prohibitive for small UAVs (which have payload capacities of <500 g) or wearable devices. Mitigation Strategies: To address size and weight constraints, researchers have developed miniaturization techniques, such as using printed strip arms on thin dielectric substrates (reducing weight by 50–70%), incorporating metamaterials (which reduce the required helix diameter by manipulating electromagnetic fields), or using collapsible/retractable structures (which allow the antenna to be folded for transport and extended during operation). However, these techniques often come with tradeoffs—printed strip arms reduce gain by 1–3 dBi, metamaterials increase manufacturing complexity, and collapsible structures reduce mechanical robustness. 2. Fabrication Complexity and Tolerance Sensitivity The high-gain four-arm helical antenna’s performance is highly sensitive to manufacturing tolerances, and its complex structure (four symmetric helical arms, precise feeding network, and uniform helix parameters) makes fabrication challenging and costly, especially for high-frequency applications (mmWave bands) or large-scale production. Tolerance Sensitivity: Small deviations in the antenna’s geometric parameters can lead to significant performance degradation. For example, a 5% deviation from the desired pitch (p) can increase the axial ratio by 1–2 dB, while a 10% deviation in arm spacing (angular symmetry) can reduce gain by 2–3 dBi. At mmWave frequencies (e.g., 28 GHz, λ ≈ 10.7 mm), even a 0.1 mm deviation in helix diameter (D) can shift the operating frequency by 5–10%, rendering the antenna incompatible with the target band. Feeding Network Complexity: The feeding network, which requires precise 90° phase shifts and amplitude balance between the four arms, is difficult to fabricate, especially for high-frequency designs. For example, a PCB-integrated feeding network for a 28 GHz antenna requires microstrip lines with widths of <0.1 mm and spacing of <0.05 mm—tolerances that are challenging to achieve with standard PCB manufacturing processes (which have typical line width tolerances of ±0.02 mm). Any deviation in line width or length can disrupt the phase shifts, increasing the axial ratio. Cost Implications: The need for high-precision manufacturing processes (e.g., laser cutting for helical arms, photolithography for PCB feeding networks, and automated assembly for arm alignment) increases the cost of the antenna. For example, a high-gain four-arm helical antenna for the mmWave band can cost 2–3 times more than a comparable patch antenna, making it less competitive for cost-sensitive applications (e.g., consumer electronics). Mitigation Strategies: To reduce fabrication complexity and cost, researchers are exploring additive manufacturing (3D printing) techniques, which can produce complex helical structures with high precision (tolerances of ±0.01 mm) at lower cost. For example, 3D-printed dielectric booms with integrated helical arms (using conductive inks) can reduce assembly steps by 50% and lower costs by 30–40%. Additionally, automated testing and calibration systems (using VNAs and robotic positioners) can be used to adjust the antenna’s parameters post-fabrication (e.g., trimming the length of the helical arms) to correct for manufacturing errors. 3. Mutual Coupling: Balancing Benefits and Drawbacks While controlled mutual coupling can enhance the antenna’s bandwidth, excessive or uneven mutual coupling remains a significant challenge, as it degrades impedance matching, axial ratio, and gain. Managing mutual coupling is particularly difficult for high-frequency designs, where the small wavelength increases the coupling coefficient between the arms. High-Frequency Coupling Issues: At mmWave frequencies, the physical spacing between the four arms (typically 0.1λ–0.2λ) is extremely small (e.g., 1–2 mm at 28 GHz). This close proximity leads to strong mutual coupling, which can shift the input impedance by ±15 Ω and increase the axial ratio by 3–4 dB. In extreme cases, excessive coupling can cause the antenna to operate in the conical mode instead of the axial mode, resulting in a significant gain reduction (5–10 dBi). Uneven Coupling Effects: Manufacturing imperfections (e.g., uneven arm spacing, variations in arm length) can lead to uneven mutual coupling between the arms. For example, if the spacing between Arm 1 and Arm 2 is 1 mm, but the spacing between Arm 2 and Arm 3 is 1.2 mm, the coupling between Arm 1 and Arm 2 will be stronger than between Arm 2 and Arm 3. This creates an amplitude and phase imbalance in the signals fed to the arms, disrupting the circular polarization and increasing the axial ratio. Mitigation Strategies: Advanced design techniques, such as electromagnetic bandgap (EBG) structures or frequency-selective surfaces (FSS), can be integrated into the antenna to reduce mutual coupling. EBG structures are periodic arrays of dielectric or metallic elements that block electromagnetic waves at specific frequencies, preventing the fields from one arm from reaching adjacent arms. For example, an EBG structure placed between the helical arms can reduce the coupling coefficient by 10–15 dB at mmWave frequencies. Additionally, machine learning (ML)-based design optimization tools can be used to predict and minimize mutual coupling during the design phase. These tools use algorithms (e.g., genetic algorithms, neural networks) to optimize the helix parameters (D, p, N) and arm spacing, ensuring that coupling remains within the desired range (0.1–0.3) across the operating bandwidth. 4. Cost and Scalability for Mass Production The high-gain four-arm helical antenna’s complex design and high-precision manufacturing requirements make it costly to produce at scale, limiting its adoption in cost-sensitive applications (e.g., consumer electronics, IoT devices). Material Costs: High-performance materials, such as silver-plated copper (for low ohmic losses), Rogers dielectric substrates (for low dielectric losses at high frequencies), and aerospace-grade FRP (for mechanical robustness), are expensive. For example, silver-plated copper wire costs 3–4 times more than standard copper wire, and Rogers substrates cost 10–15 times more than FR4 (a common low-cost PCB material). Labor Costs: The assembly of the antenna—including attaching the helical arms to the central boom, soldering the feeding network to the arms, and calibrating the phase shifts—requires skilled labor. For high-frequency designs, this assembly must be done in a cleanroom environment (to avoid dust or debris affecting performance), further increasing labor costs. Scalability Challenges: Standard manufacturing processes (e.g., manual winding of helical arms, manual alignment of the feeding network) are not easily scalable for mass production. For example, manually winding 10,000 four-arm helical antennas would take months of labor, making it impractical for consumer electronics applications (which require millions of units per year). Mitigation Strategies: To improve scalability and reduce costs, manufacturers are adopting automated manufacturing processes. For example, automated winding machines can produce helical arms with uniform pitch and diameter at a rate of 100–200 units per hour, compared to 10–20 units per hour for manual winding. Additionally, integrated manufacturing techniques—where the helical arms, feeding network, and central boom are fabricated as a single unit (e.g., using 3D printing with conductive inks)—can eliminate assembly steps and reduce labor costs by 50–60%. For cost-sensitive applications, low-cost alternative materials (e.g., aluminum instead of copper, FR4 instead of Rogers) can be used, although this may result in a 1–2 dBi gain reduction and a narrower bandwidth.

Applications and Future Trends

The high-gain four-arm helical antenna’s unique combination of high directional gain, excellent circular polarization, broad bandwidth, and environmental robustness has made it a critical component in a wide range of applications, from satellite communication and global navigation to remote sensing and 5G/6G networks. As technology advances, new trends—such as miniaturization, multi-functional integration, and AI-driven design—are shaping the future of this antenna type, expanding its capabilities and opening up new application areas. This section provides a detailed overview of the current applications of the high-gain four-arm helical antenna and explores the emerging trends that will define its development in the coming years. Current Applications 1. Satellite Communication (SatCom) Satellite communication is one of the most prominent applications of the high-gain four-arm helical antenna, due to its ability to compensate for extreme path loss, mitigate Faraday rotation, and maintain stable links in dynamic environments. SatCom systems rely on the antenna for both ground-based and space-based communication, covering applications such as broadband internet, television broadcasting, and military communication. Ground-Based Terminals: Ground-based SatCom terminals (e.g., VSAT—Very Small Aperture Terminal—systems) use high-gain four-arm helical antennas to receive and transmit signals to geostationary (GEO), medium Earth orbit (MEO), or low Earth orbit (LEO) satellites. The antenna’s high gain (15–25 dBi) ensures that the signal reaches the satellite with sufficient strength, even after traveling thousands of kilometers. The excellent circular polarization performance mitigates Faraday rotation, which is particularly problematic for GEO satellites (which operate at altitudes of ~35,786 km, requiring signals to pass through the ionosphere twice—once on the way up and once on the way down). For example, a VSAT terminal used for rural broadband internet might use a 20 dBi four-arm helical antenna operating at 12–18 GHz (Ku-band), providing download speeds of 10–100 Mbps. Space-Based Payloads: Satellites and spacecraft use high-gain four-arm helical antennas for communication with ground stations and other spacecraft. The antenna’s compact size (when optimized) and environmental robustness make it suitable for space environments, where weight, volume, and resistance to radiation and extreme temperatures are critical. For example, LEO satellites (used for Earth observation or global internet constellations like Starlink) use lightweight four-arm helical antennas with gains of 10–15 dBi. These antennas are mounted on the satellite’s exterior and operate at Ka-band (26.5–40 GHz) to support high-data-rate communication (up to 1 Gbps per user). Military SatCom: Military SatCom systems require antennas that are secure, reliable, and resistant to jamming. The high-gain four-arm helical antenna’s narrow radiation pattern reduces the risk of jamming (by focusing power away from potential jammers) and its circular polarization makes it difficult for adversaries to intercept signals (since LP jammers are ineffectiveagainst CP signals). For example, military tactical terminals used by ground troops or aircraft employ ruggedized four-arm helical antennas with gains of 12–18 dBi. These antennas operate at X-band (8–12 GHz) or Ka-band, providing secure voice and data communication with military satellites, even in hostile environments with high levels of jamming. 2. Global Navigation Satellite Systems (GNSS) Global Navigation Satellite Systems (GNSS)—such as GPS (U.S.), Galileo (EU), BeiDou (China), and GLONASS (Russia)—rely on high-gain four-arm helical antennas to receive weak satellite signals and provide accurate positioning, navigation, and timing (PNT) services. The antenna’s high gain, excellent circular polarization, and resistance to multipath fading are critical for ensuring PNT accuracy, especially in challenging environments like urban canyons or dense forests. Ground Reference Stations: GNSS ground reference stations (used for precise positioning, such as in surveying or geodetic applications) use high-gain four-arm helical antennas to receive signals from multiple GNSS constellations. The antenna’s high gain (10–15 dBi) amplifies the weak satellite signals (which typically have power levels of -150 dBm to -160 dBm at the Earth’s surface), while its narrow radiation pattern reduces interference from nearby sources (e.g., cellular towers). The excellent circular polarization performance ensures that the antenna receives both RHCP and LHCP signals (some GNSS satellites transmit in both polarizations), and the broad bandwidth allows it to cover multiple GNSS frequency bands (e.g., GPS L1: 1575.42 MHz, Galileo E1: 1575.42 MHz, BeiDou B1: 1561.098 MHz). For example, a geodetic reference station might use a 12 dBi four-arm helical antenna with a bandwidth of 1.5–1.6 GHz, enabling centimeter-level positioning accuracy. User Terminals: GNSS user terminals—such as those used in automotive navigation, UAVs, or marine vessels—use compact, low-gain (5–10 dBi) four-arm helical antennas. These antennas are designed to be small and lightweight, while still providing sufficient gain to receive satellite signals in dynamic environments. For example, an automotive GNSS antenna mounted on the roof of a car uses a 7 dBi four-arm helical antenna with a low profile (height <5 cm). The antenna’s resistance to multipath fading (due to CP) ensures that the navigation system remains accurate, even when the car is driving through urban canyons (where signals reflect off buildings) or under dense tree cover. High-Precision Applications: High-precision GNSS applications—such as autonomous vehicles, precision agriculture, or aerospace navigation—require antennas with ultra-low noise and high stability. High-gain four-arm helical antennas with integrated low-noise amplifiers (LNAs) are used in these applications. The LNA amplifies the weak satellite signals while introducing minimal noise, and the antenna’s stable gain and axial ratio (even under temperature variations) ensure that the PNT data remains reliable. For example, an autonomous vehicle might use a 10 dBi four-arm helical antenna with an LNA noise figure of <1 dB, providing sub-meter positioning accuracy in real time. 3. Remote Sensing Remote sensing applications—such as synthetic aperture radar (SAR), weather radar, and Earth observation—use high-gain four-arm helical antennas to transmit and receive electromagnetic waves, enabling high-resolution imaging and data collection. The antenna’s high gain, broad bandwidth, and environmental robustness make it suitable for these applications, which often require operation in harsh conditions (e.g., high altitudes, extreme temperatures) and high data rates. Synthetic Aperture Radar (SAR): SAR systems—mounted on satellites, aircraft, or UAVs—use high-gain four-arm helical antennas to generate high-resolution images of the Earth’s surface. The antenna’s high gain (20–30 dBi) allows it to transmit a narrow beam of radar signals, which bounce off the Earth’s surface and are received back by the antenna. The broad bandwidth of the antenna enables the SAR system to achieve high range resolution (the ability to distinguish between two points along the radar beam), while the circular polarization reduces the effects of clutter (unwanted reflections from trees, buildings, or other objects). For example, a satellite-based SAR system might use a 25 dBi four-arm helical antenna operating at X-band (8–12 GHz), providing images with a resolution of 1–10 meters. Weather Radar: Weather radar systems use high-gain four-arm helical antennas to detect precipitation, wind patterns, and other meteorological phenomena. The antenna’s high gain allows it to transmit radar signals over long distances (up to 500 km), while its narrow beamwidth ensures that the radar can accurately locate the position of precipitation. The circular polarization of the antenna helps to distinguish between different types of precipitation (e.g., rain, snow, hail), as different particles reflect CP signals differently. For example, a ground-based weather radar might use a 20 dBi four-arm helical antenna operating at C-band (4–8 GHz), providing real-time data on storm systems and severe weather. Earth Observation Satellites: Earth observation satellites use high-gain four-arm helical antennas for both communication (with ground stations) and remote sensing (collecting data on the Earth’s atmosphere, oceans, and land surface). The antenna’s dual functionality—supporting both communication and sensing—reduces the weight and volume of the satellite payload. For example, a Landsat-style Earth observation satellite might use a 15 dBi four-arm helical antenna operating at S-band (2–4 GHz) for communication and L-band (1–2 GHz) for remote sensing. The antenna’s broad bandwidth allows it to switch between the two bands, while its environmental robustness ensures that it operates reliably in the space environment. 4. 5G/6G Communication Networks The rollout of 5G and the development of 6G communication networks require antennas that can support high data rates, low latency, and reliable connectivity over long distances. High-gain four-arm helical antennas are being used in 5G/6G networks for backhaul links, small cell base stations, and user equipment, leveraging their high gain, broad bandwidth, and resistance to interference. 5G Backhaul Links: 5G backhaul links connect small cell base stations to the core network, requiring high-data-rate communication over long distances (up to 10 km). High-gain four-arm helical antennas with gains of 15–20 dBi are used for these links, operating at mmWave bands (28 GHz, 39 GHz) or sub-6 GHz bands (3.5 GHz). The antenna’s high gain compensates for the path loss in mmWave bands (which is significantly higher than in sub-6 GHz bands), while its broad bandwidth supports data rates of up to 10 Gbps. For example, a 5G backhaul link between two small cell base stations might use a 18 dBi four-arm helical antenna operating at 28 GHz, providing a reliable connection with low latency (<1 ms). Small Cell Base Stations: Small cell base stations are used in dense urban environments to enhance 5G coverage and capacity. These base stations require compact, high-gain antennas that can cover a specific area (e.g., a city block) without interfering with other base stations. High-gain four-arm helical antennas with gains of 10–15 dBi and a narrow beamwidth (15–30°) are ideal for this application. The antenna’s narrow beamwidth reduces interference by focusing power on the intended coverage area, while its broad bandwidth supports multiple 5G frequency bands. For example, a small cell base station in a shopping mall might use a 12 dBi four-arm helical antenna operating at 3.5 GHz and 28 GHz, providing high-speed 5G connectivity to shoppers. 6G User Equipment (UE): The development of 6G networks is focused on enabling new applications such as holographic communication, autonomous mobility, and ubiquitous IoT connectivity. 6G UE—such as smartphones, AR/VR headsets, and autonomous vehicles—will require antennas with high gain, broad bandwidth, and small size. Miniaturized high-gain four-arm helical antennas (with gains of 8–12 dBi and sizes of <5 cm) are being developed for 6G UE, leveraging advanced miniaturization techniques such as metamaterials and 3D printing. These antennas will operate at terahertz (THz) bands (0.3–3 THz), enabling data rates of up to 100 Gbps. For example, a 6G smartphone might use a 10 dBi four-arm helical antenna integrated into the device’s frame, providing high-speed connectivity for holographic video calls. Future Trends 1. Miniaturization and Ultra-Compact Designs The demand for compact, lightweight high-gain four-arm helical antennas is growing, driven by applications such as wearable technology, small UAVs, and 6G UE. Future research will focus on developing ultra-compact designs that maintain high performance while reducing size and weight by 50–70% compared to current designs. Metamaterial Integration: Metamaterials—artificial materials with unique electromagnetic properties not found in nature—will be increasingly used to miniaturize high-gain four-arm helical antennas. Metamaterials can manipulate electromagnetic fields to reduce the required helix diameter and number of turns, without sacrificing gain. For example, a metamaterial-inspired four-arm helical antenna might use a periodic array of metallic split-ring resonators (SRRs) around the central boom. These SRRs enhance the antenna’s radiation efficiency, allowing it to achieve a gain of 15 dBi with a helix diameter of 0.2λ (compared to 0.4λ for a conventional design). This reduces the antenna’s size by 50%, making it suitable for small UAVs or wearable devices. 3D Printing and Additive Manufacturing: 3D printing techniques will revolutionize the fabrication of ultra-compact high-gain four-arm helical antennas. Advanced 3D printing technologies—such as stereolithography (SLA) for dielectric booms and direct ink writing (DIW) for conductive arms—can produce complex, miniaturized structures with high precision. For example, a 3D-printed four-arm helical antenna for 6G UE might have a diameter of <3 cm and a length of <5 cm, with helical arms printed using conductive silver ink. This antenna could achieve a gain of 10 dBi, making it suitable for integration into smartphones or AR/VR headsets. Additionally, 3D printing allows for the fabrication of custom-shaped antennas that conform to the surface of the device (e.g., curved antennas for the edge of a smartphone), further reducing size and improving aesthetics. Foldable and Stretchable Structures: Foldable and stretchable high-gain four-arm helical antennas will be developed for applications where the antenna needs to be compact during storage and expanded during operation. These antennas will use flexible materials—such as conductive fabrics or elastomeric dielectrics—that can be folded, rolled, or stretched without degrading performance. For example, a foldable antenna for a small UAV might be folded into a 2 cm × 2 cm × 1 cm package during transport and unfolded into a 10 cm long helix with a gain of 12 dBi during flight. Stretchable antennas, made from conductive polymers, could be integrated into wearable devices (e.g., smartwatches or fitness bands) and stretched to fit the user’s wrist, while maintaining a gain of 8–10 dBi. 2. Multi-Functional Integration Future high-gain four-arm helical antennas will be integrated with other components—such as sensors, LNAs, and signal processors—to create multi-functional systems that reduce size, weight, and power (SWaP) for applications such as IoT, UAVs, and aerospace. Antenna-Sensor Integration: High-gain four-arm helical antennas will be integrated with sensors—such as temperature sensors, humidity sensors, or motion sensors—to create multi-functional devices that can both communicate and collect environmental data. For example, an IoT sensor node for agricultural applications might integrate a 10 dBi four-arm helical antenna with a soil moisture sensor and a temperature sensor. The antenna would transmit the sensor data to a central hub, while the sensor would collect data on soil conditions. This integration reduces the size of the sensor node by eliminating the need for separate antenna and sensor packages, and it reduces power consumption by sharing a single power source. Antenna-LNA Integration: LNAs will be integrated directly into the feeding network of high-gain four-arm helical antennas to reduce noise and improve signal quality. The LNA, which amplifies weak received signals while introducing minimal noise, will be fabricated using complementary metal-oxide-semiconductor (CMOS) technology and mounted on the same PCB as the feeding network. For example, a GNSS antenna for autonomous vehicles might integrate a 12 dBi four-arm helical antenna with a CMOS LNA (noise figure <1 dB) into a single package. This integration reduces the size of the antenna system by 30% and improves the signal-to-noise ratio (SNR) by 5–10 dB, enabling more accurate positioning. Antenna-Signal Processor Integration: Advanced signal processors—such as field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs)—will be integrated with high-gain four-arm helical antennas to create intelligent antenna systems that can adapt to changing environmental conditions. For example, a 5G small cell antenna might integrate a 15 dBi four-arm helical antenna with an FPGA that can adjust the antenna’s beamwidth and frequency in real time. The FPGA would analyze the received signal strength and interference levels, and adjust the antenna’s parameters to optimize performance. This integration enables the antenna to dynamically adapt to changing traffic patterns and interference conditions, improving the reliability and capacity of 5G networks. 3. AI-Driven Design and Optimization Artificial intelligence (AI) and machine learning (ML) techniques will play a key role in the future design and optimization of high-gain four-arm helical antennas, enabling faster design cycles, improved performance, and the development of novel antenna architectures. ML-Based Design Optimization: ML algorithms—such as genetic algorithms, neural networks, and reinforcement learning—will be used to optimize the geometric parameters (D, p, N, arm spacing) and material properties of high-gain four-arm helical antennas. These algorithms can quickly explore a large design space (with thousands of possible parameter combinations) and identify the optimal design that meets specific performance requirements (e.g., gain >20 dBi, axial ratio <3 dB, bandwidth >20%). For example, a neural network trained on a dataset of 10,000 antenna designs could predict the performance of a new four-arm helical antenna design in seconds, compared to hours or days for traditional electromagnetic simulation tools. This reduces the design cycle from months to weeks, enabling faster innovation. AI-Powered Performance Prediction: AI models will be used to predict the performance of high-gain four-arm helical antennas under different environmental conditions (e.g., temperature variations, moisture, interference). These models, trained on data from real-world tests and simulations, can accurately predict how the antenna’s gain, axial ratio, and impedance will change in different environments. For example, an AI model might predict that a four-arm helical antenna operating in a desert environment (temperature range -10°C to +50°C) will experience a gain reduction of <1 dB and an axial ratio increase of <0.5 dB. This allows engineers to design antennas that are robust to specific environmental conditions, without the need for expensive and time-consuming field tests. Real-Time AI Adaptation: Future high-gain four-arm helical antennas will incorporate AI chips that enable real-time adaptation of the antenna’s parameters to optimize performance. The AI chip will monitor the antenna’s performance (e.g., SNR, VSWR, axial ratio) and adjust the feeding network (e.g., phase shifts, amplitude balance) or the helix parameters (e.g., pitch, diameter, using reconfigurable components) to maintain optimal performance. For example, if the AI chip detects an increase in interference, it might adjust the antenna’s beamwidth to focus power away from the interference source, or change the operating frequency to a less congested band. This real-time adaptation ensures that the antenna operates at peak performance, even in dynamic and unpredictable environments. 4. Sustainable and Eco-Friendly Designs As the demand for wireless devices grows, there is an increasing focus on developing sustainable and eco-friendly high-gain four-arm helical antennas that reduce environmental impact. Future research will focus on using recycled materials, reducing energy consumption during manufacturing, and designing antennas that are easy to recycle at the end of their lifecycle. Recycled and Biodegradable Materials: High-gain four-arm helical antennas will be fabricated using recycled materials—such as recycled copper for the helical arms and recycled plastic for the central boom—to reduce the use of virgin materials. Additionally, biodegradable materials—such as PLA (polylactic acid) for the dielectric boom and conductive biopolymers for the arms—will be used for applications where the antenna is intended for short-term use (e.g., disposable IoT sensors). For example, a biodegradable four-arm helical antenna for agricultural IoT sensors might be made from PLA (which degrades in soil within 6–12 months) and a conductive biopolymer (made from soy protein and carbon nanotubes). This antenna would transmit soil moisture data for a growing season and then degrade, reducing plastic waste. Low-Energy Manufacturing Processes: The manufacturing processes for high-gain four-arm helical antennas will be optimized to reduce energy consumption. For example, additive manufacturing techniques (such as 3D printing) use less energy than traditional manufacturing processes (such as extrusion or machining), as they only use the material needed for the part and do not require extensive machining or assembly. Additionally, low-temperature curing processes for dielectric materials (e.g., using UV curing instead of thermal curing) will reduce energy consumption during fabrication. For example, a 3D-printed four-arm helical antenna with a UV-cured dielectric boom might use 30–40% less energy to manufacture

Overview

Design and Construction

Working Principles

Advantages and Challenges

Applications and Future Trends

18665803017 (Macro) sales@toxutech.com

Hot-selling Products

Long Range Magnetic Antenna 30Dbi Free Channel Uhf Vhf Portable 360 Degree Signal Amplifier HDTV Indoor Digital Tv Antenna

Best tv antenna for local channels hd free unlimited antenna hdfreeunlimited uhf vhf digital tv antennas

Factory Price Free Sample Digital Tv Antenna Digital Antenna for Smart Tv 4K Mini Rectangular Combination Antenna

OEM ODM High Precision Agriculture GPS Receiver Glonass BDS G-Mouse With Gnss Rtk Car Antenna

Toxu 3 band signal booster repeater 900 1800 2100 mhz mobile network booster gsm 3g 4g GSM signal booster

Customized 1.5M/3M 3-in-1 GPS GNSS + 4G/3G + WiFi Bluetooth Car Combo Antenna With SMA Connector for Vehicle IoT

5-in-1 Combo GNSS GPS 4G 3G 2G WiFi MIMO Mushroom Antenna Automotive Vehicle Navigation IoT Antenna

Universal Shark Fin Combo Vehicle Antenna GPS GNSS Car Antenna

Multifunction Shark Fin Combo Car Antenna AM/FM 4G GPS GNSS

Waterproof GNSS Timing Antenna for Base Station and Marine Navigation With High Precision GPS Timing Signal

High Precision L1/L5 Multi-Band RTK GNSS Antenna Support GPS, GLONASS, Galileo, Beidou for Aviation

Multi-Star Micro Measurement Four-Arm Helical Helix Antenna Multi-Frequency GNSS & GPS RTK for UAV Drone L1 L2 L5 Frequencies

Embedded RTK GNSS Antenna High Precision Active GPS Patch Antenna for Surveying and Navigation

High Precision Multi-frequency GNSS RTK Marine Navigation Antenna Nautical GPS GNSS Marine Antenna for RTK Marine Use

GNSS Timing Antenna With IP67 Waterproof for Marine Navigation and Base Station Positioning

Wholesale in Stock 15154 Mm Ceramic Patch Gps Glonass Antenna, Build - in Gps Gnss Ceramic Antenna

Mini Fakra Female LVDS 4-Pin GPS Fakra -Z Female Automotive Antenna Adapter Cable RF Applications Cable Communication Cables

15cm RF Cable Assembly with Fakra D Male Plug and 1.37mm Mini Cable Copper Pigtail Jumper for U.FL U.FL

Rg178 Rg316 Rf Jumper Antenna Cable Sma Coaxial Cable Assembly

Omni Directional Dual Dand 50 Km Long Range External Booster Device Mimo Outdoor Router Lte 5ghz 2g Gsm Wifi Panel 5g 4g Antenna

Outdoor 4*4 MIMO Omni Directional Fiberglass Antenna 5G NR Cellular Sub-6 GHz Dual Polarity Antenna

High Gain External 868 915MHz Flexible Rubber Whip Walkie Talkie Antenna VHF UHF SMA Communication Antenna

Free Samples Custom 180mm RF 1.13 Pigtail Cable IPX Coaxial Communication Cables Open RF Pigtail Cable

RF Connectors

FAKRA Connectors

Mini FAKRA Connectors

Ethernet Connectors

On-Board/Receptacles

Other Connectors

RF Cable Assemblys

FAKRA Assemblys

Mini FAKRA Assemblys

Ethernet Assemblys

I-PEX Assemblys

SMA Assemblys

MMCX Assemblys

MCX Assemblys

N TYPE Assemblys

Other Assemblys

Embedded Antennas

C-V2X Series

Cellular Series

Combination Series

GNSS Series

ISM/LORA Series

NFC Series

SiriusXM Series

UWB Series

Wi-Fi®/Bluetooth® Series

External Antennas

C-V2X Series

Cellular Series

Combination Series

GNSS Series

ISM/LORA Series

NFC Series

Satcom Series

UWB Series

Wi-Fi®/Bluetooth® Series

Positioning Chips and Modules

High Precision GNSS

Standard Precision GNSS

GNSS Receivers

GPS & GNSS Antenna