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Open AccessArticle

A 0.8–8 GHz Multi-Section Coupled Line Balun

EECS Department, The University of Toledo, 2801 W Bancroft St., Toledo, OH 43606, USA
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Academic Editor: Geok Ing Ng
Electronics 2015, 4(2), 274-282;
Received: 19 March 2015 / Revised: 18 April 2015 / Accepted: 24 April 2015 / Published: 30 April 2015
(This article belongs to the Special Issue Microwave/ Millimeter-Wave Devices and MMICs)
PDF [1414 KB, uploaded 30 April 2015]


In this work, we propose a wideband multi-section transforming coupled-line balun using near equal length transmission line elements. The resulting design is realized by cascading several coupled-lines with minimal discontinuities. The multi-section Chebyshev matching optimizes bandwidth at the expense of passband ripple. The proposed design delivers good impedance matching and consistent 180° phase shift over 0.8–8 GHz frequency spectrum. Furthermore, the need for vias in conventional balun designs is relaxed by replacing the short-circuited (SC) terminal by its equivalent dual open-circuited (OC) element. The proposed design is simulated, fabricated, and measured. Both simulated and measured results are in a good agreement, and show an input port matching of below −9.7 dB over the design bandwidth, with a maximum phase and amplitude imbalance of 2.1° and 0.9 dB, respectively. View Full-Text
Keywords: balun; Chebyshev; coupled-line; multi-section; stepped impedance; wideband balun; Chebyshev; coupled-line; multi-section; stepped impedance; wideband

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Itapu, S.; Almalkawi, M.; Devabhaktuni, V. A 0.8–8 GHz Multi-Section Coupled Line Balun. Electronics 2015, 4, 274-282.

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