Inset Resonators and Their Applications in Fixed/Reconfigurable Microwave Filters

This paper introduces a new so-called “inset” resonator configuration for fixed and tunable microwave filter applications. The proposed configuration has many attractive advantages in comparison with conventional structures, including miniaturized size, enhanced spurious performance, and wide tuning capabilities with the least deterioration in unloaded quality factor throughout the tuning window. For proof of concept purposes, a single inset resonator and a two-pole filter are designed, manufactured, and measured. The measurements agree very well with simulations. The measured prototypes demonstrate a wide spurious-free band, volume saving up to 50%, a wide tuning range > 41%, and a high Qu of 4004±2.4% with minimum variation throughout the tuning range.