Ka-Band Circularly Polarized Square Ring-Shaped Slot Radiator for Active Integrated Phased Array Antenna

This paper presents a right-handed circularly polarized square ring-shaped slot radiator and a multi-layer transition designed for Ka-band (19.7GHz-20.2GHz). The 12-layer stack of printed circuit board (PCB) is configured as per the manufacturing requirements. The design of square ring-shaped slot radiator and a low loss transition from co-planner waveguide (CPW) to stripline is carried out using the 12-layer PCB stack and the details are presented in the paper. To generate the circular polarization, the proposed square slot antenna is fed by a 1:2 stripline-based power divider whose outputs are in the quadrature phase. The radiating element is also embedded with vias fencing to achieve minimal cross-coupling in the array environment. The slot radiator, feed network, and transition are analyzed using a 3D electromagnetic solver. The $2.5 \%$ return loss bandwidth for $\geq 15 \text{dB}$ level and $\leq 3.5 \text{dB}$ axial ratio is achieved over the operating band. The slot radiator is also fabricated and measured.