Design Properties of a 26 GHz Circularly Polarized Square Patch Antenna With Rectangular Slot

A square microstrip patch antenna with a diagonally symmetric rectangular slot is edge-fed with a 50 $\Omega$ microstrip line and designed to produce RHCP at 26 GHz. Rectangular slots with lengths from 1.1 mm to 1.7 mm and widths from 0.05 mm to 0.30 mm are considered. Increasing the size of the rectangular slot perimeter improves the impedance match between patch and feed line while reducing resonant frequency. Larger slots are shown to damage the axial ratio. A compromise slot size of 1.4 mm $\times 0.20$ mm is suggested with best axial ratio frequency at 24.6 GHz., a minimum axial ratio of 1.27 $\mathrm{dB}$, and $S_{11}=-6$. 53 $\mathrm{dB}$ at 24.68 GHz. This optimized patch element is designed for use in a $N\times N$ array for satellite communication.