A Fully Canonical Bandpass Filter Design Using Microstrip Transversal Resonator Array Configuration

Masataka OHIRA
Toshiki KATO
Zhewang MA

IEICE TRANSACTIONS on Electronics   Vol.E99-C    No.10    pp.1122-1129
Publication Date: 2016/10/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E99.C.1122
Type of Manuscript: Special Section PAPER (Special Section on Microwave and Millimeter-Wave Technology)
bandpass filters,  transversal array filters,  even mode,  odd mode,  transmission zeros,  

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This paper proposes a new and simple microstrip bandpass filter structure for the design of a fully canonical transversal array filter. The filter is constructed by the parallel arrangement of microstrip even- and odd-mode half-wavelength resonators. In this filter, transmission zeros (TZs) are not produced by cross couplings used in conventional filter designs, but by an intrinsic negative coupling of the odd-mode resonators having open ends with respect to the even-mode resonators with shorted ends. Thus, the control of the resonant frequency and the external Q factor of each resonator makes it possible to form both a specified passband and TZs. As an example, a fully canonical bandpass filter with 2-GHz center frequency, 6% bandwidth, and four TZs is synthesized with a coupling-matrix optimization, and its structural parameters are designed. The designed filter achieves a rapid roll-off and low-loss passband response, which can be confirmed numerically and experimentally.