Microstrip Bandpass Filters with Reduced Size and Improved Stopband Characteristics Using New Stepped-Impedance Resonators

Prayoot AKKARAEKTHALIN
Jaruek JANTREE

Publication
IEICE TRANSACTIONS on Electronics   Vol.E89-C    No.12    pp.1865-1871
Publication Date: 2006/12/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e89-c.12.1865
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Emerging Microwave Techniques)
Category: Passive Circuits/Components
Keyword: 
stepped-impedance resonator (SIR),  bandpass filter,  improved stopband,  

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Summary: 
This paper proposes a new microstrip stepped-impedance resonator (SIR) used for bandpass filters with reduced size and improved stopband characteristics. A comprehensive treatment of both ends of the resonator with loaded triangular and rectangular microstrips is described. The design concept is demonstrated by two filter examples including four-resonator parallel-coupled Chebyshev bandpass and compact four-resonator cross-coupled elliptic-type filters. These filters are not only compact size due to the slow-wave effect, but also have a wider upper stopband resulting from the resonator bandstop characteristic. The filter designs are described in details. The simulated and experimental results are demonstrated and discussed.