Abstract:In high speed maglev vehicle millimeter-wave communication systems, it is required that the vehicle antenna has the characteristics of miniaturization, wide band, circular polarization and radiating sector beam. To better meet these requirements, a compact waveguide spiral array antenna with center feed is proposed. The antenna feed system adopts the form of coaxial waveguide central feed and four rectangular waveguides joint feed. By changing the size of the feed waveguide, coupling the length of the probe and placing the coaxial converter at the tail of the feed waveguide, the uniform feed of each unit is realized; the antenna low-profile unit is constituted by the helical antenna, and the circular polarization performance of the antenna is improved by using sequential rotation technique. A 28-element waveguide spiral array antenna with a center frequency of 38 GHz is designed by using full-wave electromagnetic simulation software and tested experimentally. Test results show that: in 37-39 GHz band, the antenna standing wave ratio is less than 1.41, the gain above 21.7 dB, the axial ratio less than 3.6 dB, the beam width 4.5°-4.7° at the elevation plane and 29°-29.7° at the azimuth plane. It can meet the design requirements of the vehicle antenna for millimeter wave vehicle-ground communication system.