Spatio-temporal delta-sigma modulation for shared wideband transmit arrays

Abstract

Future array-based RF transmit systems will require linear amplification to preserve the spectral integrity of simultaneously transmitted signals. Classical delta-sigma modulation, paired with an emerging class of high-power switches, can provide this linearity by using a high-speed, low-resolution quantizer and shaping the resulting quantization errors out of the signal band. The drawback is that high clock rates are required to achieve high SNR. Recently, we have proposed shaping quantization errors jointly in temporal and spatial frequency, pushing quantization errors both out of band and to nonpropagating spatial frequencies. This provides greater SNR for a given clock rate or the same SNR at a reduced clock rate relative to conventional delta-sigma modulation, while retaining its characteristic high linearity. We present an overview of the spatio-temporal delta-sigma array architecture and present the results of some preliminary hardware experiments with a small linear array.