Switchless tunable bandstop-to-all-pass reconfigurable filter

Eric J. Naglich, Juseop Lee, Dimitrios Peroulis, William J. Chappell

Research output: Contribution to journalArticlepeer-review

82 Citations (Scopus)


The theory of a new type of bandstop-to-all-pass reconfigurable filter is developed in this work. A bandstop filter structure with both source-to-load and inter-resonator coupling is implemented. The synthesis equations are manipulated such that the signals in the filter's resonators and source-to-load transmission line can be made to constructively or destructively interfere at the output port through tuning of the resonant frequency of the filter's resonators. The relationship between resonator quality factor, filter bandwidth, and the all-pass response state is shown for the first time. The theory is proven through fabrication of a bandstop-to-all-pass filter with resonator unloaded quality factors greater than 500. Measured results show that the filter can continuously tune from insertion loss of 2.1 dB in the all-pass state to insertion loss of 69 dB in the bandstop state at the center frequency of the filter. Analog tuning of the attenuation level is also shown. The capability to switch from an all-pass to a variable-attenuation bandstop response enables a spectrally aware system to operate over wide bandwidths when interference levels are low and to dynamically add bandstop responses when interference affects its performance or signal equalization is required.

Original languageEnglish
Article number6175128
Pages (from-to)1258-1265
Number of pages8
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number5
Publication statusPublished - 2012

Bibliographical note

Funding Information:
Manuscript received August 04, 2011; revised February 07, 2012; accepted February 14, 2012. Date of publication April 03, 2012; date of current version April 27, 2012. The work of E. J. Naglich was supported by the Department of Defense (DoD) through the National Defense Science and Engineering Graduate Fellowship (NDSEG) Program. This work was supported by the Defense Advanced Research Projects Agency through the Purdue Evanescent-Mode Cavity Filter Study Program.

Copyright 2012 Elsevier B.V., All rights reserved.


  • Filters
  • microwave filters
  • passive filters
  • tunable filters
  • tunable resonators

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


Dive into the research topics of 'Switchless tunable bandstop-to-all-pass reconfigurable filter'. Together they form a unique fingerprint.

Cite this