A new computer-aided tuning scheme for general lossy coupled-resonator bandpass filters based on the Cauchy method

Abstract

In this paper, a novel analytical circuit model extraction scheme for the computer-aided tuning (CAT) of general lossy coupled-resonator bandpass filters is proposed based on the Cauchy total least squares (TLS) method. The new approach enforces the realisable condition of a set of scattering rational functions that is required for a lossy two-port network in extracting the transfer and reflection characteristics of a filter. Thus, a lossy circuit model can be synthesised from the extracted scattering polynomials using the well-known coupling matrix synthesis method from the literature. To illustrate the effectiveness of the new scheme, measured data of two different kinds of dual-mode filters are used. Using the proposed method, the extracted coupling matrix can give nearly identical frequency responses with the measured data, regardless of whether the filter is well-tuned or badly detuned.

Keywords:

• bandpass filters
• Cauchy method
• characteristic function
• computer-aided tuning
• coupling matrix

Additional information

Funding

This work was supported by The Chinese University of Hong Kong.

Notes on contributors

Ping Zhao

Mr Ping Zhao received his B.Sc. degree from the Nanjing University, People's Republic of China in 2012. He is currently working toward his Ph.D. degree at The Chinese University of Hong Kong. His current research focuses on synthesis and computer-aided tuning algorithms for multiport microwave coupled-resonator networks, especially for diplexers and multiplexers with applications in cellular base station and satellite.

Ke-Li Wu

Prof Ke-Li Wu received his B.Sc. and MEng degrees from the Nanjing University of Science and Technology, People's Republic of China in 1982 and 1985, respectively, and Ph.D. degree from the Laval University, Quebec, Canada in 1989. From 1989 to 1993, he was a Research Engineer and Group Manager of the Communications Research Laboratory at McMaster University, Canada. In March 1993, he joined the Corporate R&D Division of COM DEV International, the largest Canadian space equipment manufacturer, where he was a Principal Member of Technical Staff. Since October 1999, he has been with The Chinese University of Hong Kong, where he is a Professor and the Director of the Radiofrequency Radiation Research Laboratory (R³L). He has authored and co-authored numerous publications in the areas of EM modelling, and microwave passive component, microwave filter and antenna engineering. His current research interests include partial element equivalent circuit (PEEC) and derived physically expressive circuit (DPEC) EM modelling of high-speed circuits, RF and microwave passive circuits and systems, microwave filter synthesis theory and practice, antennas for wireless terminals, LTCC-based multichip modules (MCMs), and RF identification (RFID) technologies. Prof Wu is a Fellow of the Institute of Electrical and Electronics Engineers (IEEE), a member of the IEEE MTT-8 subcommittee (Filters and Passive Components), and a Technical Program Committee (TPC) member for many prestigious international conferences, including the International Microwave Symposium. He was an Associate Editor of IEEE Transactions on MTT from 2006 to 2009. He was the recipient of the 1998 COM DEV Achievement Award for the development of exact EM design software for microwave filters and multiplexers and the Asia Pacific Microwave Conference Prize in 2008 and 2012, respectively.