An Analytical Design Method for a Wideband Differential Waveguide Directional Coupler With De-Embedding Analysis

This article demonstrates a simple, rapid, low-cost fabrication method for high-performance microwave components. A wideband differential waveguide directional coupler with complete theoretical derivation is presented for the first time based on the multihole coupling method in the Chebyshev response. The proposed coupler can be excited using a differential signal or TE20 mode. To measure the capability of the proposed coupler, a wideband multilayer integrated mode transducer is designed to excite the TE20 mode. Details of the design, simulation, fabrication, and measurements are presented. An indirect thru–reflect–line (TRL) calibration process for de-embedding measurements between two monolithically manufactured mode transducers with better measurement accuracy is provided for the first time. Liquid crystal display 3-D printer stereolithography (SLA) and copper electroplating are used to manufacture each prototype. The measured results agree with the simulation for good performance. The designed coupler shows a wide fractional bandwidth of 46.8% from 12.85 to 20.7 GHz with a coupling magnitude of 3 dB and a maximum measured deviation less than 0.6 dB. The directivity is always better than 20 dB.