Broadband Waveguide-to-Differential-Line Transition in Multi-Layer Substrates With Triple Stacked Patch in 300 GHz Band

A broadband waveguide-to-differential-line transition with a triple stacked patch is proposed for use in 300 GHz band. This transition consists of differential signal lines inserted into the waveguide region from both broad walls of the waveguide. A triple circular stacked patch element was used for broadband transmission from the waveguide to the planar differential line formed in a multi-layer substrate. Concurrently, the optimized arrangement of via holes can prevent electric field leakage efficiently and improve the transmission characteristic in a high-frequency band. The geometry of the transition was optimized through electromagnetic simulations using the finite element method. Measurements and simulations were implemented to evaluate the performance of the transition. The measured result of the transition shows the bandwidth of the $S_{11}$ below -10 dB was over 100 GHz.