A terahertz-band branch waveguide directional coupler based on micro-machining

A compact E plane of 10 dB rectangular waveguide directional coupler with different lengths of branch waveguide operating at the center frequency of 340 GHz is presented. The coupler is fabricated using the micro-fabrication technology of deep reactive ion etching (DRIE). The S-parameter is measured by the two-port vector network analyzer and the result is consistent with that of simulation, which indicates that the isolation of the coupler is better than 30 dB, the return loss is greater than 15 dB, and the best insertion loss is 2.9 dB within 330~350 GHz. With simple, compact structure and superior performance, the coupler provides a new way for designing terahertz passive circuit.