Dual-Band Bandpass Filter With Controllable Transmission Zeros Using Multimode GGW Cavity

In this letter, a class of novel dual-band bandpass filters (BPFs) with controllable transmission zeros (TZs) using a multimode groove gap waveguide (GGW) cavity is presented. The first four resonant modes of the resonator are divided into two groups and utilized to generate a dual-band response. Specifically, the resonant frequency of TE <tex-math notation="LaTeX">₁₀₂</tex-math> /TE <tex-math notation="LaTeX">₁₀₃</tex-math> is shifted close to that of TE <tex-math notation="LaTeX">₂₀₁</tex-math> /TE <tex-math notation="LaTeX">₂₀₂</tex-math> , respectively. Every two adjacent mode pairs can be regarded as a doublet model, which can produce a passband containing two poles and one zero. When a non-resonant (NRN) mode is used reasonably, two zeros can be generated. Besides, the position and number of TZs can be flexibly controlled. Multiple dual-passband filtering responses are designed and simulated for experimental verification. Two multimode filter prototypes centered at 27.8/36.0 GHz and 28.5/36.7 GHz have been fabricated and measured, respectively. The measured results are in good consistency with the simulations, which validates the design approach.