Research On UHF Omnidirectional Circularly Polarized Planar Antenna

UHF band, which refers to the frequency of300～3000MHz ultra high frequency radio wave, is widely used in modern wireless communication system. Antenna plays an important role on the merits of the communication system as a key component of wireless communication system. For all types of antenna, omnidirectional circularly polarized antenna has been getting more and more attention because of its excellent performance characteristics. With the development of WLAN and GSM technology, communication terminal is getting smaller and smaller, and a dual-band or multi-frequency function of antenna is necessary to a communication system, which makes compact broadband multi-frequency antenna be in great demand.In this paper, to satisfy the development demand of the modern wireless communication system, Dalian Maritime University Antenna and Microwave Institute develops new omnidirectional circularly polarized antennas entrusted by Dalian Tiansheng Science Equipment Co. Ltd. The author participates in the research of the project and completes the writing of the thesis. Based on the zeroth order resonator loaded arc-shaped stubs structure, broadband, miniaturization and dual-band antennas are designed by optimized of Ansoft HFSS electromagnetic simulation software, and finally the antennas are processed and tested. The main research results are as follows.(1) Good matching is achieved by proposing an inversion capacitance feeding mode, and the bandwidth of antenna is broadened by loading air layer. Two different broadband antenna structures are designed by combining with theory and simulation. Compared with the conventional structure, the two antennas’bandwidth gets a certain increase.(2) Change the number of the arc-shaped stubs around the circular patch from four to six. An antenna with a more compact structure is designed by loading microstrip tuning block technique proposed in terms of the meandering and distributed capacitance effect. The size of the antenna is greatly reduced and the excellent performance is maintained at the same time.(3) A radiation unit with two unequal length arc-shaped stubs is proposed, and the dual-band antenna consists of three radiation units. The frequency ratio can be regulated by changing the length of the two arc-shaped stubs. On this basis, a compact omnidirectional circularly polarized antenna is designed with good dual-band performance and flexible adjustment of frequency ratio.Four omnidirectional circularly polarized planar antennas presented in the paper have advantages of excellent performance, small size, light weight, low profile, easy to integrate, easy to conformal and low cost, with a broad application prospect in mobile communications, satellite communications, radar, remote sensing, aerospace and other fields.