quadrifilar helix antenna

　　Four-arm helical antenna: a high-performance weapon for wireless communication

　　At a time when wireless communication technology is developing rapidly, antennas are key devices for signal transmission and reception, and their performance directly affects the quality of communication. With its unique structural design and excellent electrical characteristics, the four-arm helical antenna stands out among many antenna types and is widely used in satellite navigation, wireless communication and other fields.

　　Structure and working principle

　　Structural composition

　　The four-arm helical antenna is mainly composed of four symmetrically distributed spiral arms, a feeding network and a reflector. The spiral arms are usually made of metal conductor materials and are wound in a spiral shape. The size of its spiral structure, such as pitch, diameter and other parameters, will be carefully designed according to the operating frequency to meet specific electromagnetic performance requirements. The function of the feeding network is to distribute the RF signal to the four spiral arms with a specific phase and amplitude to ensure that the signals between the arms work together. The reflector is generally located at the bottom of the spiral arm. Common forms include metal flat plates or cavity reflectors. Its main function is to enhance the directivity of the antenna, reduce the backward radiation of the signal, and improve the radiation efficiency of the antenna.

　　Working principle

　　The four-arm helical antenna works based on the principle of generating circularly polarized waves. When the RF signal is input to the four spiral arms through the feeding network, the current on the four spiral arms generates a rotating electromagnetic field in space due to the phase control of the signal by the feeding network, and then radiates circularly polarized waves. Circularly polarized waves have unique advantages. Compared with linearly polarized waves, they can better maintain the integrity of the signal and reduce the impact of signal fading when encountering multipath propagation, polarization mismatch and other situations. For example, in satellite communications, the signal transmission between the satellite and the ground station is easily interfered by factors such as the ionosphere and the atmosphere, resulting in changes in the polarization direction of the signal. The circularly polarized waves radiated by the four-arm spiral antenna can effectively cope with this situation and ensure the stability of communication. In addition, the multiple spiral arms of the four-arm spiral antenna work together to achieve a wider beam width and expand the coverage of the antenna, which has significant advantages in some scenarios with high requirements for signal coverage.

　　Performance characteristics

　　Wideband characteristics

　　The four-arm spiral antenna has good wideband performance and can maintain stable radiation characteristics over a wide frequency range. By reasonably designing the structural parameters of the spiral arm and the feeding network, it can cover multiple different frequency bands and meet the needs of multiple communication standards. In satellite navigation systems, such as the Global Positioning System (GPS) and the Beidou Satellite Navigation System (BDS), it is usually necessary to receive signals from multiple frequency bands at the same time. The wideband characteristics of the quadrilateral helical antenna enable it to receive satellite signals from different frequency bands at the same time, realizing precise positioning and navigation functions. Compared with traditional narrowband antennas, the quadrilateral helical antenna has obvious advantages in adapting to multi-band communications, reducing the trouble of replacing antennas due to frequency band switching, and improving the versatility and convenience of the equipment.

　　High gain and low axial ratio

　　In terms of gain, the quadrilateral helical antenna can achieve a higher gain value, generally reaching 3dBi - 6dBi, or even higher. Higher gain means that the antenna can radiate the signal energy more concentratedly in a specific direction, enhancing the transmission distance and coverage of the signal. In some long-distance communication scenarios, such as wireless communication base stations in remote areas, maritime communications, etc., high-gain quadrilateral helical antennas can effectively improve the transmission quality of signals and ensure the reliability of communications. At the same time, the axial ratio of the four-arm helical antenna is low. The axial ratio is an important indicator for measuring the purity of circularly polarized waves. The low axial ratio means that the circularly polarized waves radiated by the antenna are closer to the ideal circular polarization state, which can better reduce polarization loss and improve the signal reception efficiency. In fields such as satellite communications and radar detection that require extremely high signal quality, the low axial ratio characteristics of the four-arm helical antenna make it an ideal antenna choice.

　　Omnidirectionality and anti-interference ability

　　The four-arm helical antenna has a nearly omnidirectional radiation characteristic in the horizontal plane, and can radiate signals evenly within a 360-degree range. This omnidirectionality enables it to perform well in some scenarios that require all-round signal coverage. For example, in mobile terminal devices, no matter what orientation the device is in, it can stably receive signals to ensure the continuity of communication. In addition, since the four-arm helical antenna radiates circularly polarized waves, and many interference signals in nature are mostly linearly polarized waves, through polarization matching technology, the four-arm helical antenna can effectively suppress linearly polarized interference signals and improve its own anti-interference ability. In complex electromagnetic environments, such as areas with tall buildings in cities, there are a large number of electromagnetic interference sources. The anti-interference characteristics of the four-arm helical antenna can ensure the normal operation of communication equipment and improve the stability and reliability of communication.

　　Application scenarios

　　Satellite navigation and positioning

　　In the field of satellite navigation, the four-arm helical antenna is a key component of the satellite navigation receiver. Whether it is a vehicle-mounted navigation system, a handheld navigation device, or a navigation application in the aerospace field, the four-arm helical antenna is widely used. Taking vehicle-mounted navigation as an example, the vehicle needs to receive signals from multiple satellites in real time to determine its own position during driving. The wide-band characteristics of the four-arm helical antenna can simultaneously receive multiple frequency band signals from different satellite navigation systems such as GPS and BDS. Its omnidirectionality and anti-interference ability ensure that the vehicle can stably receive satellite signals in various environments, such as urban streets and mountain roads, to achieve accurate positioning and navigation. In the field of aerospace, the stability and reliability of the navigation signal are extremely high during the high-speed flight of the aircraft. The four-arm helical antenna provides accurate navigation information for the aircraft with its excellent performance to ensure flight safety.

　　Wireless communication base station

　　In a wireless communication base station, the four-arm helical antenna can be used to achieve stable communication between the base station and the mobile terminal. Its high gain characteristics can enhance the coverage of base station signals, reduce signal blind spots, and improve network coverage quality. In some remote areas or areas with complex terrain, such as mountainous areas and rural areas, by installing high-gain four-arm helical antennas as base station antennas, the coverage radius of base stations can be effectively expanded, allowing more users to enjoy high-quality wireless communication services. At the same time, the wide-band characteristics of the four-arm helical antenna enable it to adapt to the needs of different communication standards and frequency bands. In the construction of 5G communication base stations, it can support signal transmission in multiple frequency bands, providing strong support for the rapid deployment and wide application of 5G networks. In addition, its anti-interference ability helps to reduce interference between base stations, improve spectrum utilization, and enhance the performance of the entire communication network.

　　UAV and mobile terminal communication

　　With the rapid development of UAV technology, communication between UAVs and ground control stations is crucial. The four-arm helical antenna has become an ideal choice for UAV communication antennas due to its omnidirectionality and anti-interference ability. During the flight, the posture of the UAV changes constantly. The omnidirectional four-arm helical antenna can ensure that no matter what posture the UAV is in, it can maintain a stable communication connection with the ground control station, and realize real-time data transmission and control command reception. In mobile terminal devices, such as smart phones and tablets, the four-arm helical antenna also has potential application value. Its wide bandwidth and anti-interference characteristics can meet the needs of mobile terminals for multiple communication frequency bands, while improving the communication quality in complex electromagnetic environments, providing users with a smoother Internet experience and stable call quality.

　　Development trend

　　With the continuous evolution of wireless communication technology, higher requirements are placed on the performance and application of the four-arm helical antenna. In the future, the four-arm helical antenna will develop in the direction of miniaturization, integration and intelligence. In terms of miniaturization, as the requirements of electronic devices on volume and weight become more and more stringent, how to reduce the size of the four-arm helical antenna without reducing performance will be one of the research focuses. By adopting new materials and optimizing the antenna structure design, it is expected to achieve miniaturization of the antenna, making it more suitable for integration into various small devices. In terms of integration, the four-arm helical antenna is integrated with other functional modules, such as RF front-end, signal processing circuit, etc., to form a highly integrated antenna system, which can simplify the design and manufacturing process of the equipment, reduce costs, and improve the reliability and performance of the equipment. In the direction of intelligence, combined with artificial intelligence and machine learning technology, the four-arm helical antenna can automatically adjust its own working parameters, such as radiation direction, frequency, etc., according to changes in the communication environment, to achieve adaptive communication and further improve the performance and communication efficiency of the antenna.

　　The four-arm helical antenna plays an important role in the field of wireless communication due to its unique structure and excellent performance. With the continuous advancement of technology, it will be widely used in more fields and continue to innovate and develop, providing strong support for the development of wireless communication technology.