• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.513-520
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• 2001

In this paper, the directional coupler using three layer microstrip substrate is proposed and the design method is notified. Modified re-entrant mode coupler is the proposed structure that one layer is added on upper plane of coupled transmission lines and the floating conductor is placed on added layer's upper planes. This structure has high coupling for the increase of odd mode capacitance and also has good performance in VSWR, isolation, phase difference because the difference of effective permittivity is small in each mode. We have designed the coupler from the calculation of impedance, effective permittivity, coupling coefficient using even, odd mode analysis method. From the simulation and measurement, proposed coupler has about 2 dB more tighter coupling than conventional coupler and also has good performance in VSWR, isolation, phase difference.