Design, Fabrication and Test of a Broadband High Directivity Directional Coupler

Presented is an ultra-broadband stripline directional coupler with significant improvement in its directivity parameter which is of interest in many measurement applications. The main focus of this paper is on the influence of using shunt stubs as capacitance compensators to improve specifications of wideband directional couplers. This improvement is performed on a two-layer non-uniform line directional coupler working in 2-18 GHz band. Experimental results, for various classes of wideband stripline couplers loaded with these stubs, exhibit remarkable improvement in the directivity parameter.