Filtering phase shifter with wide bandwidth and multiple transmission zeros

A wideband filtering phase shifter is proposed using a cascaded single line and coupled line as a shunt stub of the centre-coupled line. Such kind of a shunt stub provides the possibility to achieve wideband impedance matching, wideband phase shift, and multiple controllable transmission zeros (TZs) at the same time. The coupling between the shunt stubs of the practical layout can generate extra TZs and enhance the frequency selectivity. Compared with the state-of-the-art designs, the proposed one has wider bandwidth, more TZs and medium size, and the former cannot juggle bandwidth and size. Two prototypes at 1.76 GHz are designed with the relative operating bandwidth for 45 degrees +/- 3 degrees (90 degrees +/- 4.2 degrees) phase shift of 75% (76%), five TZs and the minimum return loss of 14.7 dB.