Analytical and Numerical Study on Dual-Mode Patch Resonator Filters with Real or Imaginary Transmission Zeros

摘要

Dual-mode patch resonator-based microstrip filters with finite real or imaginary transmission zeros are discussed by combining the analytical studies with numerical investigations. The analytical study presents the coupling scheme of a dual-mode patch resonator, while the numerical simulation discusses the coupling nature between the source (input) and load (output), which constitutes the presented half-analytical model. Furthermore, the difference of in-band losses between the two different responses can also be qualified based on this model. The contribution and novelty of this work is the coupling nature between the source and load which is explained for the first time, and based on this, the half-analytical model can further estimate the transmission zeros of the microstrip patch resonator filter. For demonstration purposes, two prototype filters that exhibit transmission zeros at the real and imaginary frequencies, respectively, are developed and confirmed experimentally. The measurements agree closely with the predications.