Abstract: Based on SMIC 0.13 μm CMOS technology, a C-band 5 bit digital phase shifter was designed by using on-chip Barron, orthogonal all-pass filter and Gilbert cell. The balun divided the input signal at one end into two inverse differential signals, and then carried out vector operation on the quadrature signals generated by the quadrature all-pass filter through Gilbert cell. The bandwidth of 4.5~7.5 GHz was achieved when the phase-shifting accuracy was 11.25 degrees. The simulation results of electromagnetic field showed that the typical insertion loss of digital phase shifter was -10 dB at 4.5-7.5 GHz; the input and output return losses were better than 10.6 dB and -9.9 dB, respectively; the phase shifting accuracy of RMS was less than 3.5 degrees, the size of the layout was 1.66 mm x 0.74 mm; and the relative bandwidth of the 5 bit MMIC digital phase shifter was 50%, which was suitable for 5G low frequency communication system.