The Sound the Air Makes: High-Performance Tunable Filters Based on Air-Cavity Resonators

Yu, Ming; Yassini, Bahram; Keats, Brian; Wang, Ying

doi:10.1109/mmm.2014.2321102

Cited by 19 publications

(6 citation statements)

References 16 publications

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“…Besides, the volume of such filters is relatively large since the height of the cavity must be increased to provide room for the tuning screws/disks inside of the housing. Another group of tunable coaxial combline filters is employing horizontally sliding and/or rotational metallic or dielectric elements mounted on a common tuning post [11]- [13]. For instance, an L-band tunable λ/4 combline filter was introduced in [12] with an 11% tuning range using rotational elliptical metallic loadings.…”

Section: Introductionmentioning

confidence: 99%

Tunable Coaxial Bandpass Filters Based on Inset Resonators

Widaa

Bartlett

Höft

2023

IEEE Trans. Microwave Theory Techn.

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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.

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Section: Introductionmentioning

confidence: 99%

Tunable Coaxial Bandpass Filters Based on Inset Resonators

Widaa

Bartlett

Höft

2023

IEEE Trans. Microwave Theory Techn.

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“…Tunable RF filters are expected to play a crucial role in many evolving frequency-agile applications including multi-band cellular base stations and flexible satellite payloads [1], [2], [3], [4]. However, to replace the current fixed filter banks, tunable filters must provide similar capabilities fulfilling the stringent requirements of the various frequency-adaptable applications.…”

Section: Introductionmentioning

confidence: 99%

Widely Tunable TM-Mode Dielectric Filters With Constant Absolute Bandwidth Using Re-Entrant Caps

Widaa

Höft

2023

IEEE J. Microw.

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This paper reports octave tunable dielectric combline bandpass filters with constant absolute bandwidth (CABW) using a novel re-entrant cap tuning technique. The resonant frequency is tuned by the hollow re-entrant cap penetrating into the filter cavity as an envelope around the dielectric resonator. This mechanism of tuning provides wider tuning capabilities and better spurious performance than the conventional screw-based tuning. Also, the cap tuners can be employed effectively to tune the input-output and inter-resonator couplings simultaneously with the frequency reconfiguration, enabling a CABW over a wide frequency tuning window. For proof of concept purposes, a single widely tunable resonator is presented with octave tuning ratio of 2.64:1, high quality factor from 1705 to 5480, and spurious-free band up to 3.44• f 0 . Afterwards, two octave tunable re-entrant cap filters are designed, fabricated, and tested. The first filter is a 78% widely tunable two-pole filter with a CABW of 43.5±12% MHz, low insertion loss equals to 0.28±0.03 dB, and a compact volume of 39 cm 3 . The second design is a four-pole octave tunable bandpass filter from 2.96 GHz to 1.36 GHz with a constant 69±13% MHz bandwidth, low insertion loss better than 0.6 dB, return loss higher than 16 dB, and a compact 62 cm 3 structure. According to our own knowledge, thanks to the proposed tuning mechanism, the presented designs are the first CABW octave tunable high Q waveguide-based filters, having the widest tuning ranges over all similar state-of-the-art-designs. Cap, constant bandwidth, dielectric resonator, high-performance, re-entrant, tunable. INDEX TERMS

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“…In [5], [6], and [7] it was proposed to mount resonators in series on a common tuning column using metal or dielectric elements of horizontal sliding and rotating or one of these…”

Section: Introductionmentioning

confidence: 99%

“…structures. The structure in [5] uses a forming CAM on the rotating resonator column to change the loading capacitance of the resonator to achieve frequency adjustment. Work by using the structure design of the filter in L-band 0.95 GHz to 2.05 GHz, return loss is better than 11 dB, but change with frequency bandwidth.…”

Section: Introductionmentioning

confidence: 99%

Design of Tunable Coaxial Bandpass Filter Based on Embedded Stepped Impedance Resonators

Zhou

Huo

2023

IEEE Access

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This paper describes a method for designing tunable coaxial bandpass filters based on an inserted coaxial stepped impedance resonator (SIR). The miniaturization of the coaxial resonator is realized by the shape of the stepped impedance structure. In addition, an extended tuning range can be achieved by utilizing the SIR. A third-order tunable bandpass filter with constant absolute bandwidth is designed and fabricated for verification. The fabricated filter exhibits a wide tuning range from 2.13 GHz to 3.54 GHz (52.4%), over which the absolute bandwidth (ABW) varies within 97.5 ± 5.5 MHz (±5.6%).INDEX TERMS Coaxial resonator, constant bandwidth, wide tuning range, tunable filter.

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The Sound the Air Makes: High-Performance Tunable Filters Based on Air-Cavity Resonators

Cited by 19 publications

References 16 publications

Tunable Coaxial Bandpass Filters Based on Inset Resonators

Tunable Coaxial Bandpass Filters Based on Inset Resonators

Widely Tunable TM-Mode Dielectric Filters With Constant Absolute Bandwidth Using Re-Entrant Caps

Design of Tunable Coaxial Bandpass Filter Based on Embedded Stepped Impedance Resonators

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