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Published June 2003 | Published
Book Section - Chapter Open

Octave-bandwidth high-directivity microstrip codirectional couplers


It is a well-known problem with microstrip backward-wave couplers that directivity suffers due to the differing phase velocities of the even- and odd-mode waves. A fully-planar alternative is the forward-wave, or codirectional-coupler, but these structures have not yet been widely accepted, in part because they are complex and tedious to design. Here, we offer a simple quarter-arc geometry for loosely-coupled microstrip couplers with high-directivity that can be very quickly modeled and prototyped. A design example of a 50-110 GHz 12 dB coupler is shown. Measurements indicate that the coupler has better than 20 dB directivity over the full octave bandwidth.

Additional Information

© 2003 IEEE. The authors wish to express their thanks to the staff of American Technical Ceramics for fabrication of the Alumina substrates, and to the National Radio Astronomy Observatory for financial support. The work described in this paper was carried out in part by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

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August 19, 2023
August 19, 2023