Tunable MEMS hybrid coupler and L-band tunable filter

Tamotsu Nishino*, Yusuke Kitsukawa, Masatake Hangai, Sang Seok Lee, Shin Nosuke Soda, Moriyasu Miyazaki, Izuru Naitoh, Yoshihiko Konishi

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

12 Citations (Scopus)


Simultaneous control of frequency and coupling coefficient of a directional coupler provides a wide band tunable hybrid coupler. This hybrid coupler is combined with identical two tunable band rejection filters (BRF), to achieve a small-size wide-band tunable band pass filter (BPF). The BPF is called a reflection-type BPF and has a feature of converting rejection frequency bands of the BRF to pass frequency bands. In this paper, we derive the minimum insertion/reflection loss of the lumped element BPF and BRF, considering only the equivalent series resistance (ESR) of tuning devices. The results showed their minimum insertion loss was -5.2dB and reflection loss was -0.35dB if the ESR is 1Ω. Considering the results, we prioritize a reflection-type filter as a prospective low insertion loss tunable BPF. Even though the BRF could be miniaturized and be adapted to wide frequency region by adopting lumped elements, the hybrid coupler might restrict the wide tuning range. Then we propose new tunable hybrid coupler, which alters its coupling coefficient as well as its center frequency, to provide equal transmission and coupling coefficients in wide frequency range. Validation has been done by fabricating tunable BPF composed of 1.2/2GHz selectable MEMS hybrid coupler and 800MHz-2.4GHz seven-band MEMS tunable BRF. The total loss was around -5dB and filter size was as small as 5.2 x 12.3mm2.

Original languageEnglish
Title of host publicationIMS 2009 - 2009 IEEE MTT-S International Microwave Symposium Digest
Number of pages4
Publication statusPublished - 2009
Externally publishedYes
Event2009 IEEE MTT-S International Microwave Symposium, IMS 2009 - Boston, MA, United States
Duration: 2009 Jun 72009 Jun 12

Publication series

NameIEEE MTT-S International Microwave Symposium Digest
ISSN (Print)0149-645X


Conference2009 IEEE MTT-S International Microwave Symposium, IMS 2009
Country/TerritoryUnited States
CityBoston, MA


  • Lumped-element filters
  • Reflection-type filters
  • Tunable couplers
  • Tunable filters

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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