Circularly polarized 2-arm spiral antenna for 60-GHz applications

A wideband circularly polarized (CP) 2-arm spiral antenna is designed for 60-GHz applications in this letter. The proposed antenna is implemented on a single layer with spiral printed on the top surface of the substrate and fed in a differential way through 2 metallized via holes. Unidirectional radiation is achieved thanks to the presence of the ground plane, which is placed with a distance of one-quarter of the guided wavelength to the spiral. A cavity is mounted on the top of the spiral antenna to suppress the surface wave propagate along the substrate as well as to improve the antenna gain. Experimental results show that the prototype achieves the -10-dB impedance bandwidth from 55.2 to 66 GHz with circular polarization. The peak gain at boresight is 9.5 dBi occurring at 63 GHz and the radiation patterns are stable over the operating frequency band.