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Single stage branchline couplers reappraised
Author(s) -
Fusco V. F.,
Kerlin J. B. D.
Publication year - 1988
Publication title -
microwave and optical technology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 76
eISSN - 1098-2760
pISSN - 0895-2477
DOI - 10.1002/mop.4650011004
Subject(s) - wavelength , bandwidth (computing) , power dividers and directional couplers , hybrid coupler , center frequency , fractional bandwidth , coupling (piping) , optics , electrical impedance , physics , engineering , electrical engineering , telecommunications , band pass filter , mechanical engineering
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.