Electronically switchable microstrip bandpass filter with good selectivity

Po Ying Chang, Yo Shen Lin

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations


In this work, an electronically switchable cross-coupled microstrip bandpass filter using p-i-n diodes is proposed. The basic filter structure is based on the cascade of λ/8 parallel and anti-parallel coupled-line sections. Therefore, it occupies only about half the circuit size of conventional parallel-coupled filters. The magnetic cross-coupling is also introduced to achieve two transmission zeros in the lower and upper stopbands. In addition, by employing the four-line anti-parallel coupled microstrip structure, two more transmission zeros in the upper stopband are obtained. Two p-i-n diodes along with a common bias control circuitry are then introduced to allow the bandpass filter to be switched on and off. For design purpose, suitable equivalent-circuit for the filter is also introduced. Specifically, a switchable 4th-order microstrip bandpass filter with a center frequency of 1.5 GHz, passband insertion loss less than 2 dB, 3-dB bandwidth of 19.5%, and four transmission zeros is demonstrated. The ON-OFF isolation is better than 20 dB from dc up to 4.3 GHz.

Original languageEnglish
Title of host publicationAsia-Pacific Microwave Conference Proceedings, APMC 2011
Number of pages4
StatePublished - 2011
EventAsia-Pacific Microwave Conference, APMC 2011 - Melbourne, VIC, Australia
Duration: 5 Dec 20118 Dec 2011

Publication series

NameAsia-Pacific Microwave Conference Proceedings, APMC


ConferenceAsia-Pacific Microwave Conference, APMC 2011
CityMelbourne, VIC


  • Bandpass filter
  • coupled-line
  • p-i-n diode
  • switch
  • transmission zero


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