General Synthesis Methodology for Acoustic Wave Ladder Filters in the Bandpass Domain
Cano, Santi (Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes)
Caballero, Carlos (Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes)
Barrera, Omar (The University of Texas at Austin. Department of Electrical and Computer Engineering)
Lu, Ruochen (The University of Texas at Austin. Department of Electrical and Computer Engineering)
Verdú Tirado, Jordi (Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes)
Paco Sánchez, Pedro Antonio de (Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes)

Data:	2025
Resum:	In designing acoustic wave (AW) ladder filters, synthesis methods utilize the lowpass prototype (LP) representation to analyze bandpass responses in the normalized domain. This technique reduces the filter's polynomial order and achieves asymmetric responses by incorporating frequency-invariant reactance (FIR) elements. While this technique is particularly effective for narrowband filter designs, it faces limitations with wideband filters due to errors that arise when transforming extracted LP elements to the bandpass domain. There are different approaches for the exact modeling of AW ladder filters in the real frequency domain. However, current direct bandpass (DB) techniques for AW ladder filters cannot be generalized, as they lack flexibility in characterizing frequency-dependent input and output (I/O) phases and suffer from numerical issues during parameter extraction due to excessively large polynomial coefficients in high-order or narrowband filter designs. This work aims to address both problems: first, to generalize the DB methodology for AW ladder filters by computing the transfer function while considering the asymptotic behavior at both the origin and infinity, as well as controlling the frequency-dependent I/O phases through complex reflection zeros (CRZs). Second, to enhance numerical accuracy during parameter extraction by relying on precise root-finding methods rather than interpolated coefficients. To validate the effectiveness of the proposed DB approach, the synthesized model has been compared with a manufactured LiNbO thin-film AW ladder filter, which features a wide fractional bandwidth (FBW) of 18% and demonstrates excellent agreement between the simulated and measured responses. Finally, an 18th-order AW ladder filter has been synthesized to validate numerical stability even for narrowband filters.
Ajuts:	Agencia Estatal de Investigación PID2021-127203OB-I00
Nota:	Altres ajuts: acords transformatius de la UAB
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Acoustic-wave filters ; Bandpass domain ; Frequency transformation error ; Lowpass prototype (LP) ; Narrowband approximation ; Reduced Chebyshev (RC) ; Wideband filters
Publicat a:	IEEE transactions on microwave theory and techniques, (May 2025) , ISSN 1557-9670

DOI: 10.1109/TMTT.2025.3565809

14 p, 4.2 MB

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