Design of wideband quadrature hybrid coupler with tapered lines on the arms

In this research, a quadrature hybrid coupler has been designed and built using a substrate FR4 at a frequency of 2.5 GHz. Conventionally, the coupler has a narrow bandwidth. Tapered lines are proposed to increase its bandwidth. The line would make the series arms of the coupler curved. The measurement results on the proposed coupler indicate a reflection loss of -16.47 dB with an additional bandwidth about 100 MHz.