Circularly Polarized Twisted Quad-Ridged Horn Antenna for In-Band Full-Duplex

A circular horn antenna for in-band full-duplex communication with a quadruplet of equidistant ridges twisted to follow conical spiral contours is presented. Twisted ridges, apart from the role of extending the bandwidth, also act as polarizers. Both orthogonal linear polarizations of the ridged waveguide feed, representing transmitter and receiver sides with zero cross coupling between them in the ideal case, are transformed into the same circular polarization determined by the ridge twist direction and vice versa. This gives rise to full-duplex capability without sacrificing additional resources like different polarizations in the communication channel. For antenna designed for the frequency band 20-40 GHz, full-wave electromagnetic simulation shows Tx-Rx isolation greater that 70 dB, return loss greater than 21 dB, while boresight axial ratio as well as gain are respectively less than 2.3 dB and between 10.9 and 13.8 dBi.