Wide-stopband microstrip bandpass filters using dissimilar quarter-wavelength stepped-impedance resonators

Shih Cheng Lin, Pu Hua Deng, Yo Shen Lin, Chi Hsueh Wang, Chun Hsiung Chen

Research output: Contribution to journalArticlepeer-review

157 Scopus citations


Wide-stopband and compact microstrip bandpass filters (BPFs) are proposed using various dissimilar quarter-wavelength (A/4) stepped-impedance resonators (SIRs) for multiple spurious suppression. The use of λ/4 SIRs is essential in widening the filter stopband and reducing the circuit size. By properly arranging the individual λ/4 SIR, which has the same fundamental resonance frequency f 0, but has different spurious (harmonic) resonance frequencies, and also carefully misaligning the maximum current density nodes, several higher order spurious resonances may be suppressed so that a BPF with wide stopband may be realized. In this study, the basic concept of multiple spurious suppression is demonstrated by thoroughly investigating the spurious characteristics of the fourth-order interdigital BPFs, which consist of two different types of λ/4 SIRs. To widen the rejection bandwidth, the fourth-order coupled-resonator BPFs based on three and four different types of λ/4 SIRs are implemented and carefully examined. Specifically, a very wide-stopband microstrip BPF composed of four dissimilar λ/4 SIRs is realized and its stopband is extended even up to 11.4 f 0 with a rejection level better than 27.5 dB.

Original languageEnglish
Pages (from-to)1011-1017
Number of pages7
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number3
StatePublished - Mar 2006


  • Bandpass filter (BPF)
  • Coupled resonator
  • Microstrip
  • Quarter-wavelength stepped-impedance resonator
  • Spurious suppression


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