Frequency-Dependent Impedance Matching Synthesis Methodology for Filters or Matching Networks With Equiripple Responses
Cano, Santi (Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes)
Faura, Mario (Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes)
Garcia, Laia (Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes)
Parrón Granados, Josep (Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes)
Paco, Pedro de (Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes)

Data:	2026
Resum:	Current synthesis techniques rely on either the lowpass prototype (LP) or direct bandpass (DB) representations to analyze filtering responses, each offering its own advantages. However, all these synthesis methods are carried out under the assumption that both the source and load terminations are constant impedances. This assumption is unrealistic for most RF filter designs, as they are often required to be matched to real devices with frequency-dependent impedances [Z(f)]. The problem can be interpreted as the interaction between two networks: S, representing the filter, and S, representing the Z(f). When cascaded, these networks produce an overall response ST. This article presents a direct synthesis approach for designing general Chebyshev filters terminated with a Z(f) at one port. The proposed approach employs a Remez-like algorithm to determine the characteristic polynomials of S such that, when cascaded with S, the overall response S exhibits an in-band quasiequiripple behavior. Moreover, the proposed approach provides flexibility in controlling the return loss level (RL) of S, which is particularly useful for adjusting the out-of-band (OoB) rejection level and accommodating technological constraints in certain RF filters. The proposed method is validated through two examples with different optimality criteria: 1) an all-pole filter matched to an antenna booster, designed to approach the Bode-Fano limit by including the antenna's reflection zero (RZ) within the quasiequiripple response of S, thereby achieving the most optimal solution; and 2) a ladder filter matched to a real switch, designed excluding its RZs from S to obtain a suboptimal solution.
Ajuts:	Ministerio de Ciencia, Innovación y Universidades PID2024-159605OB-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 (AW) ; ladder filters ; Bode-Fano limit ; Cascaded filter ; Chebyshev polynomials ; Equiripple behavior ; Frequency-dependent load impedance ; Matching network
Publicat a:	IEEE transactions on microwave theory and techniques, Vol. 74, Num. 6 (June 2026) , p. 5536-5550, ISSN 1557-9670

DOI: 10.1109/TMTT.2026.3674572

15 p, 2.3 MB

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