Design of UWB uniplanar 180° hybrid employing ground slots and microstrip-slot transitions

The paper describes the design of a uniplanar 180° hybrid with an ultra wideband (UWB) performance. The device uses a single substrate and all its four ports are of microstripline type. Its construction is accomplished by first designing separately the out-of-phase and in-phase dividers. To merge the two devices into the hybrid, the input port of the in-phase power divider is split into two lines to overpass a ground slot in the out-of-phase divider. The proposed design strategy results in the 180° hybrid exhibiting 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 11GHz. The isolation between the difference and signal ports is excellent and the differential phase shift is also close to the ideal case of 180º and 0º across this band.