Common-mode suppression for balanced bandpass filters in multilayer liquid crystal polymer technology

Armando Fernández-Prieto, Shilong Qian, Jiasheng Hong, Jesus Martel, Francisco Medina*, Francisco Mesa, Jordi Naqui, Ferran Martín

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


A new multilayer differential transmission line for common-mode suppression fabricated using an organic liquid crystal polymer multilayer substrate is proposed and analysed. The structure consists of a pair of parallel strip lines printed on the top layer of the substrate that are capacitively coupled to conductor patches periodically etched in an intermediate interface. These patches are symmetrically connected to a solid ground plane by means of short-circuited high-impedance microstrip line sections and metalised via holes. The differential signal supported by the coupled strips is not significantly affected by the presence of the middle layer layout, whereas the common-mode signal propagation is strongly suppressed within a certain frequency band. When this structure is cascaded with a simple differential bandpass filter exhibiting poor common mode rejection, a good common mode response is achieved within the unperturbed differential passband. The measurements confirm a significant enhancement of common-mode rejection thanks to the use of the proposed differential lines.

Original languageEnglish
Pages (from-to)1249-1253
Number of pages5
JournalIET Microwaves, Antennas and Propagation
Issue number12
Publication statusPublished - 17 Sept 2015

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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