volume | PIER Journals

2014-09-05

A Complex Impedance-Transforming Coupled-Line Balun

Weiwei Zhang,

Mr. Weiwei Zhang

School of Electronic Engineering

Beijing University of Posts and Telecommunications

China

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Yuan'an Liu,

Dr. Yuan'an Liu

School of Telecommunication Engineering,

Beijing University of Posts and Telecommunications

China

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Yongle Wu,

Prof. Yongle Wu

School of Electronic Engineering,

Beijing University of Posts and Telecommunications

China

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Weimin Wang,

Dr. Weimin Wang

School of Electronic Engineering

Beijing University of Posts and

China

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Ming Su,

Dr. Ming Su

School of Electronic Engineering

Beijing University of Posts and Telecommunications

China

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Jinchun Gao

Dr. Jinchun Gao

School of Electronic Engineering

Beijing University of Posts and Telecommunications

China

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Progress In Electromagnetics Research Letters, Vol. 48, 123-128, 2014

doi:10.2528/PIERL14062402

Abstract

An asymmetrical coupled-line circuit is proposed to design planar microstrip balun, which has the advantages of compact structure and complex source to complex load impedance transformation. This balun consists of three pairs of coupled lines and two tapped transmission-line stubs. Based on the traditional even-odd mode technique and ABCD parameters, closed-form mathematical equations for circuit electrical parameters are obtained. To demonstrate our design theory, a practical microstrip balun is designed, simulated and measured. The results show that the return loss is larger than 25 dB, the insertion loss S₂₁ (S₃₁) 3.15 dB (3.129 dB), and the output phase difference -180.22˚ at the operating frequency. Good agreements between the simulated and measured results verify our design theory.

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Weiwei Zhang, Yuan'an Liu, Yongle Wu, Weimin Wang, Ming Su, and Jinchun Gao, "A Complex Impedance-Transforming Coupled-Line Balun," Progress In Electromagnetics Research Letters, Vol. 48, 123-128, 2014.
doi:10.2528/PIERL14062402

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