Broadband 4-bit digital phase shifter based on vector combining method

This paper presents the design and experimental results of a new broadband 4-bit digital phase shifter, based on a vector combining method. The circuits consist of an asymmetric coupled line coupler, PIN diode attenuator, symmetric coupled line coupler, and Wilkinson power combiner. The measured results exhibits a maximum RMS phase error of about 7.9 degrees and a maximum RMS amplitude error less than 1.5 dB across the frequency band from 1 GHz-3 GHz. Typical insertion loss is 16.5 dB, mean input return loss is 14.5 dB, and mean output return loss is 12 dB.