Design of 3dB Lange Coupler with Compensation

This paper designs $a\ \boldsymbol{90^{\mathrm{o}}}$ 3dB Lange coupler with low over-coupling and low return loss. The coupling line width and coupling line spacing of the Lange coupler are preliminarily cal-culated through traditional design methods. This coupler has an over-coupling situation. This paper considers the influence of the thickness of the coupled microstrip line itself and calculates the compensation amount. Finally, the deviation of the coupler's cou-pling degree and through degree from 3dB does not exceed 0.ldB in 2.8~3.6GHz.