Ultra-compact pseudoelliptic waveguide filters using TM dual-mode dielectric resonators

This paper presents a solution for ultra-compact pseudoelliptic dual-mode filters using high permittivity dielectric resonators. The basic idea consists of using a pair of degenerate resonant TM modes within a cavity loaded with a very high-permittivity puck. Nonresonating modes, instead, are exploited so as to produce a direct coupling between the input and the output of the dielectric-loaded cavity. In this way, a single cavity can provide two transmission poles and zeros, thus leading to N-pole and N-zero filters. The proposed configuration yields very compact and geometrically simple structures with resonator unloaded Q around 3000 at C-band. The geometrical dimensions of a 4-pole and 4-zero waveguide filter for C-band applications are 32×32×20 mm3 (using εr=34). Its FBW is 2.4% and the in-band IL is 0.3 dB by HFSS® simulations. The first prototype of the 4th order filter is going to be fabricated.