Wideband microstrip rat-race hybrid with via-swap phase inverter

A via-swap 180° phase inverter on the slotted ground is presented. The phase inverter with a 90° line replaces the conventional 270° line built into the microstrip rat-race hybrid. This results in a size reduction and the widening of the bandwidth. The experiments show that the proposed hybrid has a good performance from 1.5 to 2.5 GHz (f_o = 2 GHz). The bandwidth is increased from 10 to 50% and a 43% size reduction is obtained compared with the conventional rat-race hybrid.