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access icon free Switched-bandwidth SAW-based bandpass filters with flat group delay

  • Author(s): D. Psychogiou 1  and  R. Gómez-García 2
    • View affiliations
  • Source: Volume 54, Issue 7, 05 April 2018, p. 460 – 462
    DOI:  10.1049/el.2018.0082 , Print ISSN 0013-5194, Online ISSN 1350-911X
© The Institution of Engineering and Technology
Received 08/01/2018, Published 21/02/2018

Tunable surface-acoustic-wave-(SAW)-based bandpass filters (BPFs) with flat in-band group delay (τ g) and variable passband bandwidth (BW) are reported. They are based on N hybrid acoustic-wave-lumped-element-resonator (AWLR) modules shaped by one lumped-element resonator and K RF-switched SAW resonators that are arranged in a Gaussian-type source-to-load impedance-inverter network. Fractional bandwidth (FBW) tuning is achieved by reconfiguring the number of SAW resonators within the AWLR modules. Major advantages of the proposed filter concept when compared to conventional SAW BPFs are as follows: (i) they do not depend on the electromechanical coupling coefficient (kt 2) of the SAW resonators – FBW>kt 2 can be realised –, (ii) they do not require lossy elements or SAW resonators with different frequencies, and (iii) they can be tuned. For experimental-validation purposes, a 433.9 MHz two-pole/four-transmission-zero prototype was built and measured. It exhibited flat-in-band-τ g passbands with discretely-tunable BW between 0.18 and 0.45 MHz (i.e. 2.5:1 tuning ratio).

Inspec keywords: band-pass filters; surface acoustic wave resonator filters; impedance convertors

Other keywords: switched-bandwidth SAW-based bandpass filters; tunable surface-acoustic-wave-based BPF; fractional-BW tuning; two-pole-four-transmission-zero prototype; electromechanical coupling coefficient; discretely-tunable BW; hybrid AWLR modules; frequency 433.9 MHz; variable passband bandwidth; hybrid acoustic-wave-lumped-element-resonator modules; Gaussian-type source-to-load impedance-inverter network; flat in-band group delay; FBW tuning; lossy elements; K RF-switched SAW resonators

Subjects: Passive filters and other passive networks; Acoustic wave devices

References

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      • 1. Gong, S., Piazza, G.: ‘Multi-frequency wideband RF filters using high electromechanical coupling laterally vibrating lithium niobate MEMS resonators’. IEEE 26th Int. MEMS Conf., Taipei, Taiwan, 20–24 January 2013, pp. 785–788.
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      • 6. Wang, H., Chen, J., Shi, Y., et al: ‘Design of ladder-type SAW/BAW filters with constant group delay’. IEEE Ultrasonics Symp., Orlando, FL, USA, 18–21 October 2011, pp. 345–348.
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      • 2. http://abracon.com/Filters/SAW%20FILTERS/AFS14A35-1591.5-T3.pdf (accessed 5 January 2018).
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      • 3. Psychogiou, D., Gómez-García, R., Peroulis, D.: ‘RF design of acoustic-wave-lumped-element-resonator (AWLR)-based bandpass filters with constant in-band group delay’. IEEE Int. Microwave Symp., Honolulu, HI, USA, 4–9 June 2017, pp. 345–348.
http://iet.metastore.ingenta.com/content/journals/10.1049/el.2018.0082
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