Broadband Microstrip Directional Coupler using capacitive compensation and matching networks

High directivity and large bandwidth directional couplers are foreseen in future electronic systems. These devices are expected in measurement, monitoring, control and protection applications. In this work, a novel design methodology of a directional coupler using microstrip technology is proposed. This design is based on traditional coupled line theory enhanced with capacitive compensation and matching network. Using this methodology, a directional coupler is implemented in microstrip technology using FR4 substrate obtaining a large bandwidth (ranging from 1 GHz to 8 GHz) and a directivity better than 20 dB.