A Novel Circularly Polarized Half-Mode/Quarter-Mode SIW Antenna

This paper presents two low-profile right-handed circularly polarized (RHCP) antennas operating at 11GHz based on half-mode substrate integrated waveguide (HMSIW) and quarter-mode substrate integrated waveguide (QMSIW). Firstly, a substrate integrated waveguide (SIW) resonant cavity operating at 11 GHz is designed. By cutting the SIW cavity in half, a HMSIW cavity with size of 1.59λg × 1.07λg is obtained. Next, a half-octagon slot is etched on the top surface of the HMSIW cavity. Then, two square patches are placed in the slot, which gives the HMSIW CP antenna. Finally, by bisecting the HMSIW antenna directly, QMSIW antenna design with one square patch is completed, which has size of 0.86λg × 1.07λg. The proposed HMSIW and QMSIW antennas have 1.9% impedance bandwidth at 11GHz. Both antennas can achieve 0.14 GHz (1.27%) 3-dB AR bandwidth. The gain of the HMSIW and QMSIW antenna are 5.56 dBi and 5.52 dBi respectively. Furthermore, the proposed antennas can radiate RHCP beamwidth of 20°. Compared with the traditional SIW antenna, HMSIW and QMSIW antennas can reduce the size nearly 50% and 75% respectively, which are good candidates for miniaturization techniques.