A Directional Coupler for W-Band Based on Rectangular Micro-Coaxial Technology

This paper introduces a design of a branch-line directional coupler based on micro-coaxial technology. Compared to traditional microstrip lines, rectangular coaxial lines have advantages such as high frequency range, low loss, and high isolation performance, making them suitable for operation at higher frequencies. The designed branch-line coupler, with a center frequency of 91 GHz, was simulated, and the results showed that at the center frequency, the coupler's return loss and port isolation were both less than −30 dB, while the total insertion loss was less than 0.35 dB. Additionally, the phase difference between the through port and the coupled port was (90 ±3)°.