Wideband filtering phase shifter with high selectivity and low phase deviation

A wideband filtering phase shifter offering low phase deviation and high selectivity is proposed in this letter. The design incorporates phase-slope-compensation networks that allow flexible adjustment of the phase slope through impedance variation, effectively counteracting slope variations caused by changes in the delay line’s electrical length, thereby yielding a low phase‑shift error. Three pairs of coupled lines and two half-wavelength microstrip lines are employed to achieve a wide passband. Multiple transmission zeros (TZs) are introduced by the parallel coupling, source and load coupling, and quarter-wavelength short-circuit stubs, significantly improving the selectivity. Through codesign of the high-selectivity filtering structure with the phase-slope-compensation network, wide bandwidth, high selectivity, and low phase deviation can be simultaneously achieved. To demonstrate the design methodology, three prototypes were fabricated and measured, showing phase deviations in the passband of 90 ± 3.4°, 45 ± 4.2°, and 22.5 ± 2.3°, along with a rectangular coefficient of 81.2%, which validates the effectiveness of the proposed codesign approach.