Differential transmission line for common-mode suppression using double side MIC technology

A. Fernández-Prieto*, J. Martel, J. S. Hong, F. Medina, S. Qian, F. Mesa

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

11 Citations (Scopus)


A novel microstrip differential transmission line for broadband common-mode rejection is proposed. The basic unit cell of the artificial transmission line consists of a pair of coupled lines with a slot in the ground plane in which a conductor patch has been etched. This patch is symmetrically series connected to the ground plane by means of high impedance lines that act as inductors. The structure exhibits all-pass behavior under differential-mode operation because the etched pattern in the ground plane side is a virtual ground. This is because the symmetry plane is an electric wall. However, under common-mode operation the symmetry plane acts as a magnetic wall and the structure exhibits elliptic low pass characteristics. Therefore, the structure prevents common-mode propagation above a specified frequency that can be easily controlled by adjusting the length of the high impedance lines. The common-mode rejection level can be increased by cascading unit cells of this type. As an example of practical application, the structure is combined with a simple balanced bandpass filter based on folded stepped impedance resonators. The introduction of the proposed differential lines in the I/O sections significantly improves the common-mode rejection level of the conventional filter. Measured results are provided for both the differential lines and the filter.

Original languageEnglish
Title of host publication41st European Microwave Week 2011
Number of pages4
ISBN (Electronic)9782874870224
ISBN (Print)9781612842356
Publication statusPublished - 15 Dec 2011
Event41st European Microwave Conference 2011 - Manchester, United Kingdom
Duration: 10 Oct 201113 Oct 2011


Conference41st European Microwave Conference 2011
Country/TerritoryUnited Kingdom

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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