In this paper, high-gain cavity backed patch antenna arrays are proposed based on low temperature co-fired ceramic technology at 140 GHz. By introducing a substrate integrated cavity to the patch antenna element, the gain is enhanced by 3.3 dB. Moreover, a rectangular ring is loaded around the patch for better impedance matching and further gain enhancement. The final simulated maximum gain of the proposed antenna element is 9.8 dBi. Based on the proposed high-gain antenna element, a 4 × 4-element array and an 8 × 8- element array are presented. The 4 × 4-element array shows a measured maximum gain of 16.9 dBi with 9.5 GHz bandwidth (136.2–145.7 GHz) and the 8 × 8-element array shows a measured maximum gain of 21.8 dBi with 9.8 GHz bandwidth(136.7–146.5 GHz), respectively.

This paper describes a new configuration of frequency-selective structure (FSS) structures to reduce mutual coupling between the radiating elements. Also, the antenna performance before and after the implementation of FSS have been investigated. The proposed configuration provides an improvement in mutual coupling by 14 dB (measured value) with a reduced edge-to-edge spacing of 23 mm. The reduction of mutual coupling between antenna elements is interesting in the electromagnetic and antenna community. The use of electromagnetic band-gap structures constructed by microstrip technology is a way to appease the mutual coupling problem. Periodic structures such as FSS can help in the reduction of mutual coupling using their ability of suppressing surface waves propagation in a given frequency range. The goal of this present study is to use it in patch antenna arrays, keeping both the element separation smaller than λ0 for grating lobes evasion and the patch antenna size large enough to have good antenna directivity. The results showed that the proposed configuration eliminates disadvantages of similar structures presented in the previous works.