140-GHz <tex-math notation="LaTeX">TE₃₄₀ </tex-math> -Mode Substrate Integrated Cavities-Fed Slot Antenna Array in LTCC

In this paper, a TE340-mode substrate-integrated cavity (SIC) excited 2 x 2 slot antenna subarray with two TE210-mode SICs' loading is presented at 140 GHz in low-temperature co-fired ceramic. By using the TE340-mode SIC, the number of vias used in the feeding network and the area of the feeding network can be reduced compared to the feeding network composed of conventional TE10/TE20-mode SIW power dividers. The proposed simplified and miniaturized high-order mode SIC-based feeding network leads to lower transmission loss and fabrication cost and reduces the fabrication difficulty. Each pair of radiating slots is loaded by a TE210-mode SIC to improve the impedance bandwidth and the gain performance. For the proof of concept, an 8 x 8 antenna array is further designed and measured. The measured impedance bandwidth of the proposed 8 x 8 antenna array is 10.7% from 130.3 to 145 GHz for |S11| ≤ -10 dB. The measured peak gain is 20.5 dBi. The measured radiation efficiency is 59.2%.