Patent ID: 6271781
Filing Date: 2001-08-07
Classification: H03M

Abstract:
An analog-to-digital converter for converting analog input signals to parallel digital form, said analog-to-digital converter comprising:a multibit sigma-delta modulator including an input port to which said analog input signals are applied, and which produces an oversampled digital parallel data stream at its output port, the performance of said multibit sigma-delta modulator being subject to errors caused by both dynamic and static nonlinearity;nonlinear filter correction means coupled to said output port of said sigma-delta modulator for receiving said parallel digital data stream, for generating I and Q components of an estimate of said errors, and for subtracting said I and Q components of said estimate of said errors from equivalent components of said parallel digital data stream, for thereby producing I and Q components of said parallel digital data stream corrected for said nonlinearity; anda filter with at least a low-pass characteristic coupled to receive said I and Q components of said parallel digital data stream, for removing out-of-band signal components therefrom;wherein said correction means comprises:a tapped delay line coupled to said parallel digital data stream, for generating at one set of delayed samples of said parallel digital data stream at at least one tap:a lookup table coupled to said tap, for producing said I and Q components of the estimated error of said parallel digital data stream; andsumming means coupled to said parallel digital data stream and to said lookup table, for subtracting said I and Q components of said estimated error from corresponding components of said parallel digital data stream.