Tunable Combline Bandpass Filter Using Cross-Coupled Stepped-Impedance Resonators with Enhanced Characteristics

  • Kim, Yoon-Hong (Dept. of Electronic Engineering, Sogang University) ;
  • Cho, Young-Ho (Dept. of Electronic Engineering, Sogang University) ;
  • Yun, Sang-Won (Dept. of Electronic Engineering, Sogang University)
  • Published : 2008.12.31


This paper proposes a tunable combline bandpass filter with high selectivity, constant bandwidth, and good stopband performances. A filter with these characteristics is obtained by applying cross-coupling to the conventional combline bandpass filter using stepped-impedance resonators(SIRs). For high selectivity and constant bandwidth, cross-coupling is utilized and the SIR configuration is used for enhanced stopband performances. The proposed combline tunable bandpass filter with 5% of fractional bandwidth at 1.6 GHz was fabricated and tested. The measured results showed 11.6% tunability with constant bandwidth, high selectivity and enhanced stopband characteristics.


Combline Filters;Stepped-Impedance Resonator;Cross-Coupling;Microstrip Filters;Transmission Zeros;Tunable Filters


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