An inverted microstrip-fed cavity-backed slot antenna for circular polarization

This letter presents a compact circularly polarized cavity-backed four-slot antenna using an inverted configuration. The four-element slot antenna is fed by a microstrip network on the topside of the substrate, while a metallic cavity of rectangular shape is placed in the slot side of the substrate. The measured 10-dB return loss and 3-dB axial ratio bandwidths at the center frequency 6 GHz are 26.6% and 15%, respectively. The measured antenna gain for right-hand circular polarization (RHCP) is 8.7 dBi at 6.0 GHz.