Design of wideband phase shifters with low phase error using parallel inductor and capacitor for wideband antenna applications

In this paper, a phase shifter with arbitrary phase shift is presented using a coupled-line section and lumped elements. The proposed structure which consists of coupled-line section and parallel inductor and capacitor takes advantage of being realizable for phase shifts more than 90° due to relaxing the requirement for tight coupling in coupled line. The analysis shows that it is possible to achieve an arbitrary phase shift on a wide band with a low phase error. To verify the concept, three 90°, 135° and 180° phase shifters are fabricated. Measured 10-dB impedance bandwidths of 73, 62 and 56% have been obtained for 90°, 135° and 180° phase shifters, respectively, with maximum phase error of ±3°. Finally, to avoid the problems of using discrete elements, the inductor and capacitor in180° phase shifter arte realized utilizing microstrip lines. The measurement results of both designs with discrete elements and microstrip lines are a match which indicates that the proposed structure is reliable for arbitrary phase shift for high frequencies.