LOOK-AHEAD DELTA SIGMA MODULATOR WITH QUANTIZATION USING NATURAL PATTERN LOOP FILTER RESPONSES

摘要

A look-ahead delta sigma modulator reduces and simplifies the computations used to generate quantizer output values. Superposition can be applied to a loop filter response of the look-ahead delta sigma modulator. By superposition, the complete loop filter response for each output candidate vector equals the difference between a forced pattern response and a natural input signal response. The forced pattern response of the loop filter can be determined from the response to each output candidate vector with an input signal set to zero and loop filter state variables initially set to zero when determining the loop filter response for each output candidate vector. The natural input signal response of the loop filter can be determined from the response to each input signal vector with feedback data set to zero. The forced pattern response is independent of the output signal data and can be determined once for all input signal vectors xt. The natural input signal rsponse is independent of the feedback data and, therefore, need only be determined once for each output data value.