A Millimeter Wave High-Isolation Diplexer Using Selectivity-Improved Dual-Mode Filters

This letter presents an alternative method to realize millimeter wave waveguide diplexers based on high selectivity bandpass filters. A small perturbation is implemented in a dual-mode circular cavity to expand the bandwidth and significantly enhance the selectivity of the channel filter. The location of a transmission zero can be easily adjusted by properly changing the angle of a perturbing notch etched at sidewall of the cavity. A V-band diplexer prototype has been fabricated and tested. The experiment results showed good agreement with simulation results. The designed diplexer has the advantages of simple design process, quasi-planar structure, high isolation, and improved selectivity without any additional mechanical tuning element.