Circularly Polarized Patch Antenna with Miniaturized Quarter-Mode Slotted SIW Cavity

This paper presents a compact planar WIFI antenna on FR4 substrate with circular polarization (CP). It is based on a quarter mode substrate integrated waveguide (SIW) cavity with a slot near diagonal direction. CP radiation is achieved by the slot mode and a quarter SIW patch mode which are orthogonal to each other. The antenna has a compact size of 0.14 λ×0.14 λ×0.024 λ, where λ is the resonance wavelength in free space. The measured frequency band is from 2.38 to 2.51 GHz, and the measured axial ratio ( ) frequency range is from 2.445-2.475 GHz. The antenna is amid for directional CP radiation, low cost, low profile Internet of Things (IOT) device applications.