A compact balun based on microstrip EBG cell and interdigital capacitor

C. M. Lin, C. C. Su, S. H. Hung, Y. H. Wang

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


A novel compact balun (balanced-to-unbalanced) that consists of a low-pass network served by a microstrip electromagnetic bandgap (EBG) cell and a high-pass π-network formed with an interdigital capacitor is presented. This proposed approach can effectively operate the compact balun without the use of λ/4 microstrip lines to reduce the circuit area over 50% compared to the conventional Marchand balun. The core dimension of the compact balun is 0.74cm×0.7cm. The planar structure enables an efficient circuit design in printed circuit boards (PCB) without using any bonding wires, defected ground structures (DGS), or surface mounted devices (SMD). A compact balun operating in the 3 GHz band has been implemented in a FR-4 PCB. From the measured results, the return loss of the input port is better than 15dB over the band from 2.6 to 4 GHz. The amplitude and phase imbalances are less than 1.4dB and 3° with the 20% operational bandwidth ranging from 2.7 to 3.3 GHz, respectively.

Original languageEnglish
Pages (from-to)111-118
Number of pages8
JournalProgress in Electromagnetics Research Letters
Publication statusPublished - 2009

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials


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