Design of Ku-band High Directivity Directional Coupler

This paper introduces a method to improve the directivity of directional coupler. Adding open-stub to each section of the parallel coupling line. The open-stub is equivalent to a capacitance element to compensate the discontinuity of two adjacent coupled line junction. The simulation results show that this method can effectively improve the directivity of stripline directional coupler. In this paper, a Ku-band stripline directional coupler is designed, the directivity value of the directional coupler is -17dB without open-stubs. However, the directivity of the directional coupler improves 13dB with open-stubs.