A high directivity coupler design using an inductive compensation technique

This paper presents the technique to enhance a directivity of a microstrip parallel coupler. The technique increases the directivity by equalizing phase velocities with inductive components at coupled and direct ports of the coupler. Two configurations based on the technique are proposed and their design equations are derived. The practicability of the proposed technique is demonstrated with both singly and doubly inductive compensation at 0.9GHz on RF60-0600 substrate, whose improved directivity performance of such uncompensated microstrip parallel coupler about 6 and 33dB, respectively.