A Wideband MMW Microstrip-line Antenna with five rings for dual circular polarization

A wideband millimeter wave (MMW) microstrip-line antenna with five rings for dual circular polarization is proposed. The antenna is constructed by five sequentially fed microstrip-line rings, with one ring located in the center as feed line and the other four rings surrounding the center ring as a circular array. The circular polarization is realized by rings arranged in appropriate phase, which is controlled by the radii of rings. Moreover, the antenna possesses symmetric structure and two ports for dual circular polarization. Simulation results show that the antenna obtains an operating bandwidth of 12% across the 37.2～42 GHz, and the realized gain is higher than 6.7 dBic with the highest gain of 8 dBic at 38.5 GHz. Besides, the antenna is etched on one substrate and easy to fabrication.