A 2–24-GHz 360° Full-Span Differential Vector Modulator Phase Rotator With Transformer-Based Poly-Phase Quadrature Network

Abstract

This article presents a differential vector modulatorbased phase rotator (PR) performing 360° full-span phase interpolation over a first-ever decade-wide instantaneous bandwidth from 2 to 24 GHz. The proposed PR employs a three-stage transformer poly-phase network with high-precision and ultrawide-bandwidth, two highly linear 5-bit variable gain amplifiers (VGAs), a differential series-shunt-series inductor peaking load network for bandwidth extension and an open-drain buffer. It is implemented in a standard 65-nm bulk CMOS process with a chip area of 1.2 mm x 1.8 mm. The measurement results demonstrate the maximum rms quantization phase error of 1.22° within a 1.5-dB output magnitude variation for full 360° interpolations from 2 to 24 GHz and the -3-dB magnitude bandwidth is up to 19 GHz, respectively. Moreover, due to the wideband high-quality in-phase/quadrature (I/Q) signal generation and high-precision I/Q interpolation of the VGAs, the PR can perform full-span phase synthesis with a constant set of phase shift code settings for all the operating frequencies. For interpolating 22.5°/15° phase step over the 360° full-span, the “one-code” setting operation achieves an rms phase error of 1.56°/1.42° from 3.5 to 22.5 GHz without any frequency-dependent code/look-up table (LUT), tunable element, or band-selection switch. Furthermore, with the “one-code” setting operation, the modulation tests demonstrate measured rms error-vector-magnitude (EVM) values below 5% for a 50-kSym/s QPSK signal from 3.3 to 22.3 GHz and for a 16-quadratic-amplitude modulation (QAM) signal from 2.7 to 22 GHz.