A 23.8–30.4-GHz Vector-Modulated Phase Shifter With Two-Stage Current-Reused Variable-Gain Amplifiers Achieving 0.23° Minimum RMS Phase Error

This letter presents a millimeter-wave (mm-wave) vector-modulated phase shifter (VMPS) for phased-array applications. To improve the phase-shift accuracy without drastically increasing design complexity, the proposed VMPS structure employs variable-gain amplifiers (VGAs) that offer $2\times $ better resolution at their low-gain states compared to their high-gain states. A two-stage current-reused structure is also proposed to implement the desired VGAs with minimal layout complexity, negligible gain penalty, and no extra power. Moreover, the proposed VMPS can maintain its phase-shift accuracy even at lower voltage gains. Fabricated in 40-nm CMOS, the prototype core consumes 11 mW from a 1.1-V supply and occupies a core area of 0.19 mm ² . At 28 GHz, with a phase resolution of 0.61°, the measured RMS phase error is 0.23° at the maximum gain and remains $ < 0.5^\circ $ at 9-dB gain back-off. With a fixed set of VGA’s codewords, the RMS phase error and gain variation error are, respectively, lower than 1° and 0.24-dB over a bandwidth of 23.8–30.4 GHz.