Design of a Multilayer Ultra-Wideband Directional Coupler

Abstract:
The design of a planar, ultra-wideband, five-section 3 dB directional coupler is presented. In order to achieve the necessary tight coupling at the center section for the desired ultra-broadband behavior, a novel multilayer configuration is used. This multilayer structure leads to a compact, robust and easily producible realization. The design procedure itself is done without a time-consuming full-wave analysis and can be applied easily to other coupler designs. The manufactured coupler has a coupling and insertion loss of 3.4 dB ± 1.1 dB and an isolation and return loss of better than 14 dB in the operating bandwidth between 3.1-10.6 GHz.