Wideband and Stable-Gain Cavity-Backed Slot Antenna With Inner Cavity Walls and Baffle for X- and Ku-Band Applications

A $2\times2$ element cavity-backed waveguide slot antenna array, which covers the entire Ku-band and a part of the X-band satellite communication (SatCom) frequency bands is designed. The antenna is fed by a slot on the feed waveguide of WR75, which feeds four radiating slots through a cavity structure. To enhance impedance matching, inner cavity walls are introduced on the resonant cavity structure. A baffle is also placed between radiating slots to reduce mutual coupling and increase operating bandwidth and gain. The feeding slot, radiating slots, cavity, cavity inner walls, and baffle are optimized to achieve the highest bandwidth, gain, and low cross-polarization (Xpol) levels. The proposed $2\times2$ element array antenna is fabricated by aluminum via traditional computer numerical control (CNC) milling. The measured results demonstrate that the $2\times2$ element antenna array has an operating bandwidth of 48.2% (from 9.6 to 15.7 GHz) for return loss greater than 10 dB and broadside gain varies from 11.5 to 14 dBi over the entire operating band. The measured 1 dB down gain bandwidth is 43.4% (from 10.1 to 15.7 GHz). Xpol levels are better than −28 dB of both E- and H-planes throughout the band. The antenna has a compact aperture size of $1.88\lambda _{\mathrm {o}} \times 1.85\lambda _{\mathrm {o}}$ ( $44.5\times43.9$ mm) at the center frequency ( $\lambda _{\mathrm {o}}$ refers to the wavelength of free space at 12.7 GHz−23.6 mm). Furthermore, the antenna has a low profile which means the height is only $0.6\lambda _{\mathrm {o}}$ including the baffle. The design which spans a part of the X-band, the entire TX and RX bands of the Ku-band, can be utilized in the direct broadcast from satellite (DBS) applications, which use linear polarization such as vehicular and airborne terminals especially unmanned aerial devices in the array form. In addition, to demonstrate the viability of the suggested antenna for high gain applications wideband $2\times4$ element antenna array with an appropriate feed network is developed through only simulation.