High Directivity Coupler Suppressing Leak Coupling with Cancellation Circuit of Wilkinson Divider

Kazuhisa YAMAUCHI  Akira INOUE  Moriyasu MIYAZAKI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E93-C   No.7   pp.1032-1037
Publication Date: 2010/07/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E93.C.1032
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Microwave and Millimeter-Wave Technologies)
Category: 
Keyword: 
directional coupler,  microstrip coupler,  directivity,  divider,  isolation,  

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Summary: 
A high directivity microstrip coupler suppressing leak coupling with a cancellation circuit of a Wilkinson divider is presented. The presented coupler utilizes a cancellation circuit between a coupling port and an isolation port of the conventional microstrip coupler to enhance the isolation. The cancellation circuit consists of the Wilkinson divider, the multistage attenuator, and the phase offset line. The frequency to enhance the isolation is controlled by the attenuators. As the directivity is improved without the modification of the conventional coupler, the cancellation circuit can be applied to the fabricated conventional couplers. The measured directivity of the presented 1/18 λ coupler is improved from 4.8 dB to 43.0 dB at 2.6 GHz, compared with the conventional 1/4 λ coupler with -20 dB coupling. Simultaneously, the 27.4% relative bandwidth with the 20 dB directivity is achieved.