An implementation scheme and test results of 25 dB high power microstrip directional coupler is proposed. In order to test high power microwave signal accurately, microstrip coupler should have strong anti-cross interfere capability,good band flatness,low insertion loss. In this paper, compensation techniques of inductor are adopted to poise the odd mode and even mode. Design parameters are obtained by binary concept and capacitive compensation theory. The simulation and optimization are completed by soft using Ansoft HFSS. High performance and high power microstrip directional coupler is implemented. Microstrip circuit is made by substrate using Rogers RT/ duroid 6002. Solid state transmitter of 10 W and 300 W are used to test anti-cross interfere capability. The results show that, within the operating frequency range, the insertion loss is less than 0.3 dB, and the ripple level of the coupling factor better than 1 dB, and the directivity more than 9 dB.
