Patent ID: 8604957

Claim:
An apparatus for converting a continuous-time, continuously variable signal into a sampled and quantized signal, comprising: an input line for accepting an input signal that is continuous in time and continuously variable; a plurality of processing branches coupled to the input line, each of said processing branches including: (a) a continuous-time quantization-noise-shaping circuit, (b) a sampling/quantization circuit coupled to an output of the continuous-time quantization-noise-shaping circuit, (c) a digital bandpass filter coupled to an output of the sampling/quantization circuit, and (d) a line coupling the output of the sampling/quantization circuit back into the continuous-time quantization-noise-shaping circuit; and an adder coupled to outputs of the plurality of processing branches, wherein a center frequency of the digital bandpass filter in each said processing branch corresponds to a minimum in the quantization noise transfer function for the continuous-time quantization-noise-shaping circuit in the same processing branch, and wherein each of said digital bandpass filters includes: (a) a quadrature frequency downconverter that generates in-phase and quadrature outputs, using cosine and sine sequences with a frequency corresponding to the minimum in the quantization noise transfer function, (b) a first moving-average filter coupled to the in-phase output of the quadrature frequency downconverter, (c) a second moving-average filter coupled to the quadrature output of the quadrature frequency downconverter, and (d) a quadrature frequency upconverter that uses cosine and sine sequences with the frequency corresponding to the minimum in the quantization noise transfer function.