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Distortion mechanisms in varactor diode-tuned microwave filters

Research output: Contribution to journalArticle

  • BE Carey-Smith
Original languageEnglish
Pages (from-to)3492 - 3500
Number of pages9
JournalIEEE Transactions on Microwave Theory and Techniques
Journal issue9
StatePublished - Sep 2006


This paper examines the broadband distortion behavior in flexible filters employing varactor-diode tuning elements. Series- and parallel-resonant varactor-loaded transmission-lines, both commonly used in bandpass and bandstop microwave filters, are analyzed. Nonlinear Volterra-series analysis is employed to determine the second- and third-order distortion ratios dependent on the frequencies of the incident signals. It is shown that in a bandpass filter (employing parallel tuned resonators), maximum distortion occurs in the passband, while in a bandstop filter (employing series tuned resonators), minimum distortion occurs at the minimum-loss passband. The analysis is verified by practical measurement of filters employing the two modes of resonators

Additional information

Publisher: IEEE Rose publication type: Journal article Terms of use: Copyright © 2006 IEEE. Reprinted from IEEE Transactions on Microwave Theory and Techniques. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Bristol's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to By choosing to view this document, you agree to all provisions of the copyright laws protecting it.

Research areas

  • microwave filters, distortion, tunable filters

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