Circularly Polarized Self-Diplexing SIW Cavity Backed Slot Antennas

In this communication, three novel self-diplexing circularly polarized (CP) antenna configurations are presented in substrate integrated waveguide (SIW) technology for dual-band communication systems. The antennas provide left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and different sense of polarization at two bands. An asymmetric cross-slot on top of a rectangular SIW cavity is used as the basic radiator. A different sense of polarizations over the bands is obtained by changing the feed position and the slot orientation. The CP bands can be tuned independently. In each case, 3 dB axial ratio bandwidth is at least 0.81%. Working principle of the antennas is explained with the help of full-wave electromagnetic simulations. Finally, the three X-band prototype antennas are fabricated and tested for experimental validation. All of them have high front-to-back ratio (FTBR) and low cross-polarization level.