Compact Microstrip Wideband Cross-Coupled Inline Bandpass Filters With Miniaturized Stepped-Impedance Resonators (SIRs)

Shao Chan Tang, Pei Cheng Chu, Jen Tsai Kuo*, Lin Kun Wu, Chun Hung Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

This paper presents a class of reduced footprint inline microstrip bandpass filters capable of covering bandwidth up to 20% as well as good flexibility in establishing various cross-couplings for creating transmission zeros. The resonating elements are quarter-wave stepped-impedance resonators (SIRs), which have a wide upper stopband in nature. To achieve size miniaturization, the low-impedance segment of each SIR is implemented as a thick-trace ring and configured in a spiral form, and the high-impedance section is deformed to accommodate the low-impedance section. An interlaced coupling structure is proposed to enhance the coupling limited by the downsized coupled segments of adjacent resonators. In addition, by properly routing the associated shorted stubs, the structure can easily establish cross-coupling between nonadjacent resonators. Thus, compact SIR filters in an inline arrangement can be achieved to have either narrow or wide passbands with multiple transmission zeros. Two such circuits with sharp transition bands and upper stopband extension are synthesized, fabricated, and tested. The measured results show good agreement with simulated data. The circuit areas together with the performances of the experimental filters are compared with those in existing literature.

Original languageEnglish
Pages (from-to)21328-21335
Number of pages8
JournalIEEE Access
Volume10
DOIs
StatePublished - 2022

Keywords

  • Bandpass filter
  • compact
  • cross-coupling
  • microstrip
  • miniaturization
  • stepped-impedance resonator (SIR)
  • transmission zero
  • wideband

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