2 × 2 Slot Spiral Cavity-Backed Antenna Array Fed by Printed Gap Waveguide

A wideband circularly polarized slot spiral antenna array excited by a printed gap waveguide (PGW) feeding network is presented in this paper. The equiangular slot spiral is etched on the top wall of the substrate integrated cavity (SIC) in which TE120 mode is excited. Due to excitation of this mode, electric field distribution in two halves of the substrate integrated cavity is the same in magnitude and 180° out of phase. Therefore, the slot spirals are fed differentially by this cavity and become independent of the complex vertical balun structures. The sequential feeding is implemented by PGW technology, which results in high efficiency of the array structure. Moreover, by employing SIC and PGW technologies, this antenna is compatible with low cost printed circuit board (PCB) technology. A prototype of the proposed antenna was fabricated and measured to evaluate the antenna performance. The fabricated antenna array shows the -10 dB impedance bandwidth of 23.7% and the 3 dB AR of 22.5% with the measured RHCP gain of 12.3 dBic.