Wireless user terminal and system having high speed, high resolution, digital-to-analog converter with off-line sigma delta conversion and storage

Abstract

A wireless communications apparatus and corresponding system having an improved DAC operable at higher speed than heretofore achievable which exploits the sigma-delta principle in a different way. More particularly, the invention comprises a wireless user terminal () and corresponding system () that implement a digital-to-analog conversion circuit () including a storage means (), such as a read only memory, for storing delta-sigma analog sequences corresponding to all possible values of a digital input () coupled to a plurality of one-bit digital to analog converters (). Each of the digital-to-analog converters () are clocked by multi-phase clocks, such that each phase applied to each one of the digital-to-analog converters () is delayed with respect to one another by the oversampling period. An summer is coupled to each digital-to-analog converter () for summing each output from each digital-to-analog converter () to generate an analog output. Hereby, the digital-to-analog conversion circuit () according to the invention emulates a delta-sigma digital-to-analog converter having both high speed and high resolution.