New design techniques and architectures for highly-reconfigurable and continuously-tunable RF filters using acoustic-wave and planar-microwave resonators
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Date
2025-12-31
Authors
Nasser, Mohammed
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Publisher
University College Cork
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Abstract
The rapid growth of wireless networks, for example, the fifth and sixth generation (5G/6G) of wireless is increasingly calling for highly-versatile radio frequency (RF) front-ends capable of sensing the electromagnetic spectrum and dynamically adapting to changing spectral conditions and user needs. To facilitate their deployment, ultra compact and highly-reconfigurable RF filters need to be incorporated in their RF transceivers to facilitate detection of low-power RF signals amid high-power, dynamically-allocated interferers and adaptive band selection. Acoustic-wave-resonator (AWR)-based filtering technologies have been the main filtering technology for mobile RF transceivers due to their ultracompact size and their inherent high unloaded quality factor (Q) ≈ 2,000-10,000. However, they are limited by static transfer functions (TFs) and very narrow fractional bandwidths (FBWs) <0.5% that are approximately equal to 0.4–0.8kt2 (kt2 is the electromechanical coupling coefficient). Microwave planar-based RF filters such as those based on microstrip, stripline and coplanar waveguide (CPW) resonator technologies exhibit wider FBWs (2-10%) and can tune their TFs in terms of frequency, bandwidth (BW), and number of bands. However, they suffer from low Q (≈50-100) and despite being tunable their tuning range is limited to 1.5:1 and to frequencies up to L-band.
This thesis is centered around new design techniques, tuning concepts and integration approaches for continuously-tunable RF filters using AWRs and highly-miniaturized planar microwave resonators. Specifically, it introduces new classes of: i) quasi-elliptic acoustic-wave lumped-element resonator (AWLR)-based RF filters with continuously tunable frequency and BW, and multi-configurable tunable modes of operation (i.e., adapted between multiple bandpass, bandstop, all-pass and all-stop operational modes) while having enhanced FBWs (i.e.,>0.4–0.8kt2) as needed for effective spectrum management in multi-standard communications; ii) reflective and quasi-reflectionless multi-band AWR-based bandpass filters (BPFs) to facilitate multi-band operability and minimize RF signal reflections, improving the signal-to-noise ratio (SNR), and iii) widely-tunable tune-all planar-based BPFs with ultra-wide centre frequency (fcen) and BW tunability of almost two octaves within the most crowded part of the Frequency Range 1 (FR1) spectrum using a new-type of a switchless manifold two-filter approach.
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Keywords
Acoustic wave filter , Band-pass filter (BPF) , Kt2-enhancement , Bandpass filter (BPF) , Band-pass filter (BPF) , Reconfigurable filter , Bandstop filter (BSF) , Acoustic wave resonator (AWR) , Surface acoustic wave (SAW) resonator , Tunable filter , Multilayer , Dual-band , High-frequency filter , High quality factor (Q) , Octave tuning
Citation
Nasser, M. R. A. 2025. New design techniques and architectures for highly-reconfigurable and continuously-tunable RF filters using acoustic-wave and planar-microwave resonators. PhD Thesis, University College Cork.