Self-Quadruplexing Circularly Polarized SIW Cavity-Backed Slot Antennas

In this communication, three self-quadruplexing circularly polarized (CP) antennas are presented in substrate integrated waveguide (SIW) technology for quad-band wireless services. The proposed antennas radiate from four unequal length T-shape slots etched on a square SIW cavity. The antennas are excited by four microstrip lines. The T-shape slot placed at each corner of the cavity creates orthogonal electric fields having 90 degrees phase difference, which leads to CP radiation. The first antenna provides left hand circular polarization (LHCP), while the second antenna provides right hand circular polarization (RHCP) in all the bands. The third antenna offers LHCP in two bands and RHCP in other two bands. The sense of polarization can be changed by simply changing the slot orientation. Furthermore, the bands can be tuned almost independently over a wide range of frequency. For all the antennas, the measured isolations among the ports are more than 26 dB, front-to-back ratio (FTBR) is more than 15 dB, and the measured gain is at least 5.2 dBi.