RF CMOS integrated on-chip tunable absorptive bandstop filter using Q-tunable resonators

Byungguk Kim, Jangjoon Lee, Juseop Lee, Byunghoo Jung, William J. Chappell

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)


A new approach for protecting sensitive receivers through large attenuation and its realization on-chip is presented for the first time. This paper demonstrates the use of absorptive bandstop filters that gives anomalously deep notches for a given quality factor. This approach is used in a fabricated design example to isolate a sensitive wideband LNA from interference in 45-nm SOI complementary metaloxide-semiconductor (CMOS). For reconfigurable RF front-ends, a frequency-agile design is newly developed with Q tunable resonators because an absorptive bandstop filter must balance both intrinsic Q of the resonators and the resonant frequency of the filter. Therefore, the design requires variable resistors, variable capacitors, and intimate coupling of inductors of disparate values. The layout of overlapping inductors on closely spaced metal layers is required for proper absorptive properties. The size of one filter presented in this paper is 310 by 340 μm, making it the smallest absorptive bandstop filter demonstrated so far. Despite using small-size, on-chip low-Q resonators in the bandstop filter design, an attenuation level from 31 to 63 dB and a frequency tuning range from 2.9 to 4.3 GHz are achieved with potential to suppress potential interference or an image frequency signal.

Original languageEnglish
Pages (from-to)1730-1737
Number of pages8
JournalIEEE Transactions on Electron Devices
Issue number5
Publication statusPublished - 2013


  • Absorptive bandstop filter
  • Bandstop filter
  • Complementary metal-oxide-semiconductor (CMOS)
  • Frequency-agile filter
  • Image rejection
  • Integrated filter
  • Interference rejection
  • On-chip
  • RF receiver front-end
  • Resonator filter

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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