Circular Polarized Square Slot Antenna Based on Slow-Wave Substrate Integrated Waveguide

The design of a compact substrate integrated waveguide (SIW) cavity-backed circular-polarized antenna using a slow wave structure is proposed in PCB technology. Based on a multilayer substrate, this topology includes internal metallized blind via holes connected to the bottom conductive plane, inducing the physical separation of electric and magnetic fields in the SIW cavity. Hence, a slow wave effect is obtained, allowing a 47% reduction of the antenna cavity in comparison with its classic SIW antenna counterpart. Moreover, by asymmetrically inserting an inductive via into the patch region, a degenerated mode allows both a circular polarization and an enlargement of impedance bandwidth. Measurements and simulations are in good agreement in terms of radiation pattern and circular polarization with a return loss of 15 dB and a gain of 4.8 dBic.