A 2–24GHz 360° full-span differential vector modulator phase rotator with transformer-based poly-phase quadrature network

Abstract

This paper presents a differential vector modulator phase rotator performing 360° full span phase interpolation over a first-ever decade-wide instantaneous bandwidth (2GHz-24GHz). A wideband poly-phase network based on folded transformer 90° couplers generates accurate differential quadrature signals with low passive loss (2dB) over a decade bandwidth. Two 5-bit linear digital variable gain amplifiers (VGAs) scale the quadrature signals, which are then combined for the target phase interpolations. Our phase rotator occupies a very compact chip size (1.2mm-by-1.8mm) in a standard 65nm CMOS process. Moreover, our design does not require any tuning element, band selection switch, or frequency-dependent code compensation/look-up table, ensuring that each phase interpolation code can be used for all the in-band operation frequencies. Additionally, the maximum RMS quantization phase error is only 1.22° within 1.5dB output magnitude variation for full 360° interpolation from 2GHz to 24GHz.