Wideband Microstrip 180 $^{\circ}$ Hybrid Utilizing Ground Slots

The letter describes the design of a wideband microstrip 180° hybrid, which makes use of two sides of a single-layer substrate. The device is formed by the out-of-phase and in-phase dividers which are suitably unified. By making use of ground slots and microstrip to slot transitions all four its ports are of microstrip type. The hybrid exhibits a well-balanced power division between the output ports and good quality return losses of the out-of-phase (difference) and in-phase (summation) ports across the band from 3 to 9 GHz. The isolation between the output ports is better than 10 dB. The isolation between the difference and summation ports is greater than 40 dB and the phase characteristics are close to the ideal 180° and 0°.