A Wideband CMOS Linear Digital Phase Rotator

This paper presents a 10-bit wideband Cartesian phase rotator with a novel linear digital VGA implemented in a 0.13 um CMOS process. The VGA topology is robust to device modeling uncertainties and PVT variations. The system provides 7.8 dB voltage gain with -3 dB bandwidth of 7.6 GHz. A maximum phase error of 2deg has been achieved for a phase shifting range of 360deg with 32 phase steps of 11.25deg. The capability to compensate for mismatched quadrature inputs is also demonstrated.

I. Introduction

The beam forming and electrical steering capabilities of a phased array system depend mainly on the phase shifting resolution. Various on-chip phase shifters have been reported in the past [1]–[8]. In general, a phase shifter functions as an adjustable delay element and can be classified into two categories depending on whether the signal is broadband or narrowband in nature.