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

Abstract

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× 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 mm2. 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∘ 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.