A compact microstrip wideband arbitrary branch-line coupler with coupled-line impedance-transforming structures

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Pages (from-to)256-270
Journal / PublicationElectromagnetics
Issue number3
Publication statusPublished - 1 Apr 2013


Abstrct A novel coupled-line impedance-transforming structure with two parallel short-circuit stubs is proposed to design a wideband branch-line coupler with arbitrary power division in this article. In order to design this modified wideband branch-line coupler, analytical synthesis equations are obtained. As typical examples, four wideband branch-line couplers with different power dividing ratios are presented. The widest 20-dB return loss and isolation fractional bandwidth in these four numerical examples is almost 38%. Finally, two microstrip branch-line couplers operating at 1 GHz are fabricated and measured. One of these couplers has equal power division and a measured 13.9-dB return loss and isolation fractional bandwidth of 32.8%. The other one has 3-dB unequal power division and a measured 12.7-dB return loss and isolation fractional bandwidth of 37.6%. Obviously, this proposed branch-line coupler has several advantages, including a wide band, a compact size, an unequal power division, easy implementation (simple structure), and an analytical design method. Copyright © 2013 Taylor and Francis Group, LLC.

Research Area(s)

  • branch-line coupler, coupled line, unequal power division, wide band