Design of directional coupler with an arbitrary realizable power ratio and identical output phase

This document presents the design of a directional coupler that gives a relatively arbitrary power division ratio and identical output phases at the output ports. The arbitrary power ratio is realized by adopting broadside-coupled striplines. Improved Schiffman phase shifters are integrated into the circuit to achieve identical output phases within a certain frequency range. The circuit is also skillfully reshaped to ensure the two output ports lying on the same side with a compact size. Based on the simulation results by using the commercial EM software, the responses of the reshaped circuit have little difference compared with the traditional one.