Development of wideband low-loss directional coupler with suspended stripline and microstrip line

A novel K/Ka band directional coupler with low insertion loss over a wideband is proposed. The design combines the advantages of suspended stripline (SS) and microstrip line (MS). This novel directional coupler is suitable for high output power detection and can be seamlessly integrated with low-loss SS power combiners and MS circuits. The measured insertion loss is less than 0.2 dB, coupling is within 20.5-22 dB with more than 15 dB directivity, and return loss of all ports is better than 15 dB over 20 30 GHz.