A Frequency Tunable Circulator with 70-dB Isolation Using Reflection Coefficient Controller for Arbitrary Load Impedance

Donghyun Lee, Gisung Yang, Jong Hyuk Park, Byung Wook Min

Research output: Contribution to journalArticlepeer-review


This article presents a method to increase the isolation and control the operating frequency of a circulator. The internal signal flow of a circulator is analyzed, and the through-port reflection to cancel out the leakage signal is investigated. A reflection coefficient controller (RCC) is designed to ensure that such reflection occurs at the operating frequency. In addition, the operating frequency can be tuned by using two varactor diodes of the RCC for an arbitrary value of the antenna impedance. The experimental results from the proposed method show isolation of 70 dB and an insertion loss of -1.4 dB at the operating frequency. Moreover, the operating frequency can be changed from 2.2 to 2.8 GHz with high isolation for an arbitrary antenna impedance.

Original languageEnglish
Article number9440675
Pages (from-to)3797-3803
Number of pages7
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number8
Publication statusPublished - 2021 Aug

Bibliographical note

Funding Information:
Manuscript received February 1, 2021; revised March 23, 2021; accepted April 19, 2021. Date of publication May 25, 2021; date of current version August 5, 2021. This work was supported in part by the CTO Future Technology Center, LG Electronics, and in part by the Institute of Information and Communications Technology Planning and Evaluation (IITP) Grant funded by the Korean Government (MSIT) under Grant 2020000218. (Corresponding author: Byung-Wook Min.) Donghyun Lee, Gisung Yang, and Byung-Wook Min are with the Department of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, South Korea (e-mail: bmin@yonsei.ac.kr). Jong-Hyuk Park is with Hyundai Mobis, Yongin 449-910, South Korea.

Publisher Copyright:
© 1963-2012 IEEE.

All Science Journal Classification (ASJC) codes

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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