Single stage branchline couplers reappraised

V. F. Fusco, J.B.D. Kerlin

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


At present the preferred single stage branchline coupler is the conventional quarter wavelength branchline device. This paper illustrates that the quarter wavelength branchline coupler is a special case of a more general form that allows an infinite range of single stage branchline couplers to be developed for any degree of coupling and for any chosen center frequency. We term these couplers fractional wavelength branchline couplers. It is shown that the characteristics of the fractional wavelength branchline coupler are dependent on the design constraints imposed. The design can be constrained either by choice of branch lengths or by selection of line characteristic impedance. For comparison theoretical and experimental results for bandwidth, coupling, and isolation are shown for an example operating at 10 GHz.
Original languageEnglish
Pages (from-to)364-367
Number of pages4
JournalMicrowave and Optical Technology Letters
Issue number10
Publication statusPublished - Dec 1988


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