Delay-Sum Group Delay Controller with Low-Loss and Low-Phase Variation

Kyutae Park, Byung Wook Min

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


This article presents a group delay controller (GDC) circuit based on the delay-sum method. The proposed circuit can potentially be employed in a self-interference cancellation circuit in full-duplex radio systems. The proposed GDC splits the input signal into two signals with different magnitudes and then combines them in-phase at the output port. Variable group delay can be achieved by changing the power ratio of the two signals. The power dividing ratio (PDR) is changed by employing a variable power divider/combiner (VPD/VPC). The resonant reflective loads substitute for a single varactor diode such that the limited PDR of the VPD/VPC does not degrade the group delay variation range of the GDC. The resonant load can provide infinite PDR by covering open to short susceptance. In addition, asymmetrically connecting the VPD and VPC provides a flatter group delay response. As a result, the delay-sum method enables the proposed GDC to provide low and constant insertion loss while providing low insertion phase variation. The proposed delay sum GDC is demonstrated at 2.5 GHz. The measured insertion loss is only 2.18± 0.28 dB with a continuously controlled relative group delay of 430 ps. Furthermore, the insertion phase variation is only 7.3° at 2.5 GHz, and input/output matchings are maintained for all delay settings.

Original languageEnglish
Article number9288951
Pages (from-to)825-832
Number of pages8
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number1
Publication statusPublished - 2021 Jan

Bibliographical note

Funding Information:
Manuscript received July 25, 2020; revised October 6, 2020 and November 16, 2020; accepted November 21, 2020. Date of publication December 9, 2020; date of current version January 5, 2021. This work was supported by the IITP Grant funded by the Korea Government (MSIT) under Grant 2020000218. This article is an expanded version of that presented at the IEEE MTT-S International Microwave Symposium (IMS 2020), Los Angeles, CA, USA, June 21–26, 2020. (Corresponding author: Byung-Wook Min.) The authors are with the Department of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, South Korea (e-mail:;

Publisher Copyright:
© 1963-2012 IEEE.

All Science Journal Classification (ASJC) codes

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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