Broadband Differential-Line-to-Waveguide Transition in Multi-Layer Dielectric Substrates With an X-Shaped Patch Element in 280 GHz Band

A broadband differential-line-to-waveguide transition covering the 260–300 GHz band was developed in this study. This transition consists of a differential line inserted from the narrow wall of the waveguide that excites an X-shaped patch located at the waveguide center. As the two corners of the patch are excited electromagnetically via differential signal lines in the opposite phase, orthogonal current components that radiate the TE10 mode into the waveguide are generated. Broadband operation is achieved via the double resonance of the X-shaped patch and a cavity formed by the via-hole arrangement with apertures patterned in a multi-layer substrate. The transition geometries are optimized via electromagnetic simulation using a finite element method. Transition performance is evaluated through measurements and simulations.