• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.6
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• pp.548-553
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• 2004

In this paper, single, two, and three-section microstrip directional couplers are implemented for realizing the high directivity characteristics. The achievement of the high directivity with microstrip configuration is carried out by the distributed capacitor to decrease the even and odd mode phase difference. Capacitive compensation is performed by gap coupling of open stub formed in sub-coupled line. Therefore, insertion loss and power handling capability are not affected by the gap coupling. The proposed structure is easy to fabricate and incorporate another microwave device due to the planner microstrip. We designed and fabricated single, two, and three-section directional coupler with 20 ㏈ coupling. In spite of microstrip structure, the capacitive compensation structure shows 30 ㏈, 27 ㏈, and 25 ㏈ of directivity in single, two, and three-section directional couplers, respectively.