FLEXIBLE AND PROGRAMMABLE DELTA-SIGMA ANALOG SIGNAL CONVERTER

摘要

Processing apparatus (20) that directly samples and quantizes a complex envelope of a bandlimited waveform centered at a predetermined carrier frequency. An oversampling delta-sigma modulator (21) samples and quantizes the input signal to a single bit data stream. A serial-to-parallel converter (22) converts th e single bit data stream into a parallel bit stream. A digital decimation filter (23) digitally filters the parallel bit stream to produce an estimate of the baseband in-phase and quadrature components of the input signal. In-phase and quadrature video filters (27, 2 8) generate in-phase and quadrature samples that are output from the analog signal converter. A controller (26) and a plurality of digital-to-analog converters (25) are used to center noise shaping nulls of the delta-sigma modulator around the carrier frequency. The controller sets the spacing between nulls of the serial-to- parallel converter to maximize the signal-to-noise ratio of the analog signal. The controller controls the decimation filter to set the sample times of thereof to sample the carrier in quadrature so that the coefficients are programmed to foam a bandpass filter at the carrier frequency and programs the coefficients of the video filters to form bandpass filters at the decimated carrier frequency.