A new class of compact, high-Q, tunable coaxial filters is presented in this paper based on a novel inset resonator concept. The tuning concept is based on the displacement of movable resonators inside a properly modified metallic housing which features wide tuning capabilities and stable high Qfactor performance with minimum variation throughout the tuning window. Various prototypes are designed and implemented to demonstrate and validate the proposed concept. A single tunable inset resonator is first designed and measured showing distinctive results of a 43% tuning range, stable high-Q of 4100±4%, spurious-free band up to 3.8•f0, and volume-saving up to 50% when compared to the conventional combline and halfwavelength structures. The design procedure for constant absolute bandwidth (CABW) tunable filters is then presented, and two different tunable inset filters are designed and implemented. Firstly, a manually tunable four-pole filter is demonstrated with the merits of a wide 39.3% tuning range, while maintaining a constant bandwidth of 116 MHz±6%, and a stable high-Q of 1820±6%. Next, an automatically tunable 3rd-order inset filter is designed and measured using high-accuracy piezomotors. Similarly, the measured results exhibit a wide 1.3 GHz tuning range from 2.65 GHz -3.95 GHz with a stable insertion loss that is less than 0.35 dB, a return loss that is better than 15 dB, and a good spurious performance up to 2.8•f0. To our own knowledge, the proposed tuning technique and tunable components represent state-of-the-art tuning range and stable high-Q with minimal variation when compared with similar loaded-waveguide designs.

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.

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A compact fully-reconfigurable C-band pseudoelliptic bandpass filter for the applications of next-generation flexible satellite systems is introduced. The filter is realized using a dual-mode TM-mode dielectric resonator attributing ultra-high miniaturization and volume saving > 70%. A wide 790 MHz tuning window is obtained from 4.72 -5.51 GHz with a constant bandwidth of 50 MHz. Additionally, two independently reconfigurable transmissions zeros are introduced through the use of a doublet configuration and non-resonating modes. A piezomotor-based fixture is utilized for accurate fine-tuning. The measured results show good agreement with simulations. The prototype filter has demonstrated high-Q measurements across the whole tuning band (> 500) while maintaining a low insertion loss of less than 1 dB and return loss higher than 18 dB.

This paper reports a new tuning technique for TM mode dielectric resonators and filters. The proposed concept is based on the use of a hollow envelope (cap) to tune the resonant frequency instead of/in addition to the conventional intruding screw/rod-based method. The presented technique provides highly desirable advantages of tunable components including the wider tuning capabilities, simple configuration, and the improved Q factor. For proof of concept purposes, a tunable resonator is designed, fabricated, and measured. Also, a comparison with the conventional tuning technique is presented. The measured results demonstrate a wide tunability > 90% with a high Q-factor up to 3119 promoting the application of the proposed mechanism in high-performance tunable components.