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Computer‐aided diagnosis of lossy microwave coupled resonators filters
Author(s) -
Wang Rui,
Xu Jun
Publication year - 2011
Publication title -
international journal of rf and microwave computer‐aided engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.335
H-Index - 39
eISSN - 1099-047X
pISSN - 1096-4290
DOI - 10.1002/mmce.20537
Subject(s) - resonator , scattering parameters , filter (signal processing) , microwave , lossy compression , waveguide filter , m derived filter , coupling (piping) , phase (matter) , topology (electrical circuits) , band pass filter , acoustics , cauchy distribution , prototype filter , electronic engineering , mathematical analysis , mathematics , filter design , computer science , physics , optics , materials science , engineering , telecommunications , electrical engineering , statistics , quantum mechanics , combinatorics , metallurgy
A method is presented for extracting the coupling matrix (CM) and the unloaded Q from the measured (or electromagnetic simulated) scattering parameters of a lossy coupled resonators bandpass filter. The method can be used for computer‐aided tuning of a microwave filter. The method consists of two elements: 1) a three‐parameter optimization method is proposed to obtain the unloaded Q (assuming all the resonators with the same unloaded Q) and to remove the phase shift of the measured S ‐parameters caused by the phase loading and the transmission lines at the input/output ports of a filter; 2) the Cauchy method is used for determining characteristic polynomial models of the S ‐parameters of a microwave filter in the normalized low‐pass frequency domain. Once the characteristic polynomials of the S ‐parameters without phase‐shift effects are determined, the CM of a filter with a given topology can be extracted using well‐established techniques. Three diagnosis examples illustrate the validity of the proposed method. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.