Synthesized Microstrip Diplexer with Coplanar Waveguide Feeding Based on Composite Resonators

A coplanar waveguide feeding microstrip diplexer based on composite resonators (CRs) is proposed. Transmission zeros (TZs) in each channel are well arranged. The proposed diplexer is designed by virtue of the impedance transformation of open stubs and J-inverters, which simplifies the diplexer design and miniaturizes the circuit size. The overall size of the proposed diplexer is about 0.367 λ
_g
×0.408 λ
_g
. The insertion loss in the two channel are 0.3 dB and 0.4 dB due to the proposed structure. Isolation characteristic is higher than 23 dB. Simulation results validate the proposed diplexer design method.