Development of a Broadband and High-Gain Circularly Polarized Array of Multilayer Slot Antennas for X-Band Wireless Communication Networks

This paper presents a wideband cavity-backed slot antenna array designed for X-band wireless communication systems. The antenna element consists of a circular slot combined with a cross-slotted patch; both are fed by an L-shaped microstrip line through proximity coupling to extend the impedance bandwidth and gain. The reduction of beam squint in the radiation patterns, caused by the asymmetric feed line, is achieved through intelligent optimization of the dimensions and position of the cross slot on the patch. Additionally, a back cavity is included to provide unidirectional radiation and enhance gain. The antenna exhibits right-hand circularly polarized (RHCP) radiation patterns with high gain over a wideband frequency range. To further improve the axial ratio (AR) bandwidth and gain, the antenna is utilized in a $2\times 2$ array configuration with a sequential rotation feed network. The overall dimensions of the proposed array are $1.42{\lambda }_0\times 1.42{\lambda }_0\times 0.45{\lambda }_0$ , where ${\lambda }_0$ represents the wavelength at the center frequency of 10 GHz. The fabricated array is then tested, and the measurements show an impedance bandwidth of 60% (7 GHz-13 GHz) with $\left|S_{11}\right|<-10$ dB, a 3 dB AR bandwidth of 42% (7.45-11.65 GHz), and a peak gain of 11.14 dB. The simulated and measured results exhibit good agreement, validating the effectiveness of the design.