A Reconfigurable Full D-Band Waveguide Coupler Based on Asymmetric Compensated Branch

In this letter, a novel reconfigurable full D-band (110–170 GHz) branch waveguide coupler (BWC) is proposed based on an asymmetric compensated branch (ACB). By unilaterally introducing a compensated slot while maintaining the other side of the branch, the proposed design enables precise coupling tuning. The coupling-compensated principle and design methodology are discussed in detail. For demonstration, a four-branch reconfigurable BWC with a tunable coupling degree from 10 to 20 dB in 2-dB step is fabricated using computer numerical control (CNC) milling technology. Measured results in the full D band show that the coupling amplitude imbalance is less than ±0.5 dB for six states, and the return loss is better than 18 dB, which are all good agreement with the simulated ones.