Design of Dual- and Triple-Passband Filters Using Alternately Cascaded Multiband Resonators

• Published in: IEEE transactions on microwave theory and techniques Vol. 54; no. 9; pp. 3550 - 3558
• Main Authors: Chen, C.-F., Huang, T.-Y., Wu, R.-B.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.09.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Band pass filters; Chebyshev approximation; Circuit properties; Circuits; Coupling circuits; Coupling coefficient; Coupling coefficients; Degrees of freedom; Dual band; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; external quality factor; Filtering theory; Frequency filters; Mathematical analysis; microstrip filter; Microstrip filters; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwave filters; Microwaves; Oscillators, resonators, synthetizers; Passband; Q factor; Resonator filters; Resonators; Specifications; stepped-impedance resonator; transmission zero; Freedom degree; Microstrip filters; transmission zero; Q factor; Stepped impedance device; Specification; external quality factor; Simulation; Coupling coefficient; stepped-impedance resonator; Band pass filter; microstrip filter; Frequency response; Passband; Coupled resonator; Cascade connection
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2006.880653

A novel method for designing multiband bandpass filters has been proposed in this paper. Coupling structures with both Chebyshev and quasi-elliptic frequency responses are presented to achieve dual- and triple-band characteristics without a significant increase in circuit size. The design concept is to add some extra coupled resonator sections in a single-circuit filter to increase the degrees of freedom in extracting coupling coefficients of a multiband filter and, therefore, the filter is capable of realizing the specifications of coupling coefficients at all passbands. To verify the presented concept, four experimental examples of filters with a dual-band Chebyshev, triple-band Chebyshev, dual-band quasi-elliptic, and triple-band quasi-elliptic response have been designed and fabricated with microstrip technology. The measured results are in good agreement with the full-wave simulation results