Wideband and Ultrawideband Phase Shifter Designs Based on Low-Pass/Bandpass/High-Pass Networks

This paper presents the design of wideband and ultrawideband 90° phase shifters using coupled-line sections and low-pass/bandpass/high-pass networks with inductors and capacitors. By relaxing the tight-coupling requirement, the proposed phase shifters are realized with much easier fabrication process. It is demonstrated how the embedded low-pass/bandpass/high-pass networks make the phase shifters wideband. The fabricated phase shifters with low-pass, bandpass, and high-pass networks using discrete elements achieve the operating bandwidths of 44%, 83%, and 107%, respectively. Later, discrete elements are replaced by their equivalent short and open microstrip lines to make the system monolithic and more reliable, especially at higher frequencies. The measured results show approximately equal bandwidths of 40%, 87%, and 94% for the phase shifters with low-pass, bandpass, and high-pass networks, respectively.