Design of novel microstrip directional coupler for differential signal decoupling

This study describes a concept of a novel microstrip directional coupler for differential signal decoupling, which can be used to digital signal overhearing on printed-circuit-boards. The complete design method is proposed with rules given analytically. Considered methodology is suitable for synthesis of couplers with low coupling factors, which have negligible influence on the transmission in main line. Theoretical considerations are confirmed by numerical tests performed using full-wave simulator for the practical case of the coupler project and measurement results. The authors demonstrate that the accuracy of the design method is sufficient for practical system design both in terms of required coupling factor and influence on the main transmission line.