volume | PIER Journals

2009-11-09

A Compact Balun Based on Microstrip EBG Cell and Interdigital Capacitor

Chih-Ming Lin,

Dr. Chih-Ming Lin

Department of Electrical Engineering

National Cheng-Kung University

Taiwan

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Chun-Chi Su,

Dr. Chun-Chi Su

Department of Electrical Engineering

National Cheng-Kung University

Taiwan

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Shih-Han Hung,

Dr. Shih-Han Hung

Department of Electrical Engineering

National Cheng-Kung University

Taiwan

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Yeong-Her Wang

Prof. Yeong-Her Wang

Institute of Microelectronics, Department of Electrical Engineering

National Cheng-Kung University

Taiwan, ROC

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Progress In Electromagnetics Research Letters, Vol. 12, 111-118, 2009

doi:10.2528/PIERL09092904

Abstract

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 0.74 cm x 0.7 cm. 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 15 dB over the band from 2.6 to 4 GHz. The amplitude and phase imbalances are less than 1.4 dB and 3° with the 20% operational bandwidth ranging from 2.7 to 3.3 GHz, respectively.

Citation

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Chih-Ming Lin, Chun-Chi Su, Shih-Han Hung, and Yeong-Her Wang, "A Compact Balun Based on Microstrip EBG Cell and Interdigital Capacitor," Progress In Electromagnetics Research Letters, Vol. 12, 111-118, 2009.
doi:10.2528/PIERL09092904

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