A novel design of printed ridge gap waveguide‐based 0‐dB backward‐wave coupler

This article presents the design and implementation of a 0‐dB coupler based on Gap Waveguide (GW) technology. The proposed coupler is considered as the first backward‐wave 0‐dB realized using this technology. It operates at a central frequency of 30.5 GHz and maintains good performance regarding isolation and directivity all over the band. A parametric sweep is carried out to study the effect of the coupling section dimensions on the coupler performance to achieve nearly 0‐dB coupler. The design is based on finite difference time domain (FDTD) analysis using CST microwave studio and Finite Element Method (FEM) using Ansoft HFSS for validation. The novelty of this article is that the achievable coupling section structure is considered as a genuine design for most 0‐dB couplers for different operating frequency bands with its corresponding unit cell design based on GW technology. To validate this concept, the design steps are applied to four different frequency bands without changing the shape of the coupling section. The corresponding GW feeding networks are implemented on different materials for different couplers: Rogers RT5880, Rogers RO3003, and Rogers RO4350B. Furthermore, one of the couplers is fabricated and tested. The measured and simulated results show an acceptable agreement.