Fabrication of compact microstrip line-based balun-bandpass filter with high common-mode suppression

Chia Mao Chen, Shoou Jinn Chang, Yen Liang Pan, Cheng Yi Chen, Cheng Fu Yang

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


A new type of balun-bandpass filter was proposed based on the traditional coupled-line theory and folded open-loop ring resonators (OLRRs) configuration. For that, a new device with both filter-type and balun-type characteristics was investigated and fabricated. Both magnetic and electric coupling structures were implemented to provide high performance balun-bandpass responses. The fabricated balun-bandpass filters had a wide bandwidth more than 200 MHz and a low insertion loss less than 2.51 dB at a center frequency of 2.6 GHz. The differences between the two outputs were below 0.4 dB in magnitude and within 180 ± 7° in phase. Also, the balun-bandpass filter presented an excellent common-mode rejection ratio over 25 dB in the passband. An advanced design methodology had been adopted based on EM simulation for making these designed parameters of OLRRs, microstrip lines, and open stubs. The measured frequency responses agreed well with simulated ones.

Original languageEnglish
Article number985064
JournalMathematical Problems in Engineering
Publication statusPublished - 2014

All Science Journal Classification (ASJC) codes

  • Mathematics(all)
  • Engineering(all)


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