Novel wideband microband coupler based on defect place structure

The invention discloses a Broad Band micro-strip coupler based on a defect ground structure. The Broad Band micro-strip coupler comprises a defect ground structure, a microstrip structure signal layer and ports; wherein the defect ground structure comprises a ground layer, an open ring and an interdigital line. The frequencies f0 and f1 of the defect ground structure are determined according to the technical index force factor C, the characteristic impedances Z0 of the terminals, the central frequency fc and the parameter (Epsilon r, h)of the microstrip; f0 is less than fc, and fc is less than f1(as showed in formula I) and the value of f1/f0 is determined according to the requirement of the broad band; the size of the defect ground structure is determined according to f0, f1 and (Epsilon r, h). The width W, the distance and the length p of the coupled microstrip lines are calculated through simulation software and then are optimized to satisfy design requirements. Compared with conventional directional couplers with parallel coupled lines, the Broad Band micro-strip directional coupler added with a defect ground structure which is provided with an open ring and an interdigital line is effectively increased in work bandwidth and the defect ground structure can improve the coupling factor of the coupler.