UWB phase shifter with parallel stubs terminated with virtual short and ground slots

The paper describes the design of an ultra wideband (UWB) microstrip phase shifter employing open and short-circuited parallel stubs loading a main transmission line. To make the device fully planar, the design uses a virtual short and ground slots terminating the stubs. The proposed design strategy is demonstrated in examples of 45° and 22.5° phase shifters. The designed phase shifters exhibit an approximately constant phase shift with fine amplitude characteristics over UWB.