Compact multimode-resonator diplexer with wide upper-stopband and high isolation

摘要

A microstrip diplexer with upper-stopband and high isolation is presented in this paper. A multimode resonator is designed by using stub-loaded circuit, which can be employed as the common resonator to replace the common matching network of the diplexer. The resonant frequency of the multimode resonators can be adjusted flexibly by changing the length of the open stub and shorted stub, respectively. The proposed diplexer working at center frequencies of 1.8 and 3.5 GHz with over 45 dB isolation is finally simulated, fabricated, and measured. The measured results are in good agreement with the simulated ones.