A 20dB stripline coupler with CPWG transitional structure

Two designs of 20dB directional stripline couplers with high isolation are presented. Each of the couplers consists of a stripline coupler and a transitional structure. Grounded coplanar waveguide (CPWG) and microstrip line are utilized as transitional structures, respectively. The presented designs of coupler have advantages of compact size, high isolation, and simple design procedure. The stripline coupler with CPWG and the one with microstrip line are simulated and the results are compared. The coupler with CPWG transitional structure is fabricated and measured. With the return loss of higher than 23 dB, the isolation of fabricated 20dB stripline coupler with CPWG is higher than 43 dB over the frequency range from 2.6GHz to 4.7 GHz.