Design of microstrip bandpass filters with suppression of spurious harmonics

Jen Tsai Kuo*, Eric Shih, Meshon Jiang, Wei Hsiu Hsu, Wei Ting Huang, Sin Ping Chen, Wei Cheng Lee

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review


Coupled corrugated microstrip lines, suspended coupled microstrip lines, over-coupled end stages and stepped impedance resonators (SIR's) are used to construct bandpass filters that suppress spurious harmonics. These designs can greatly enhance the attenuation levels in stopband, extend the upper stopband width to at least two times, and improve the passband symmetry of a microstrip bandpass filter. The first two structures are designed to equalize the phase velocities of the eigen-modes in the longitudinal direction, so that filters of medium and wide bandwidths can be implemented with effective suppression of spurious harmonics at twice the center frequency (2fo). Over-coupled stages are used to effectively compensate for the phase difference resulting from the un-equal even- and odd-mode phase velocities of coupled stages in a parallel-coupled line filter. SIR filters are found to have a wide stopband -up to more than eight times the passband frequency. Both simulation and measured results are presented for each structure.

Original languageEnglish
Pages (from-to)357-365
Number of pages9
JournalJournal of the Chinese Institute of Electrical Engineering, Transactions of the Chinese Institute of Engineers, Series E/Chung KuoTien Chi Kung Chieng Hsueh K'an
Issue number4
StatePublished - 11 2003
Externally publishedYes


  • Corrugated coupled lines
  • Microstrip filter
  • Over-coupled stages
  • Spurious harmonic
  • Suspended microstrips


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