Microstrip directional coupler with flat coupling and high isolation
Based on the open-circuited slotline to realise capacitive compensation, a microstrip directional coupler with high isolation is investigated. Meanwhile, by adding external matching networks at the input/output ports, bandwidth is enhanced and a flat coupling is obtained. Centred at 2.4 GHz, a 3 dB directional coupler is designed, fabricated and examined. Both simulated results and measured data are presented, and good agreement between them is observed.