Patent ID: 9621175
Date: 2017-04-11
CPC Classifications: H03M

Claim:
1. 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 bandpass noise-shaping circuit, (b) a sampling/quantization circuit coupled to an output of the bandpass 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 bandpass 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 stopband region in a quantization noise transfer function for the bandpass noise-shaping circuit in the same processing branch, wherein each of said digital bandpass filters includes: (a) a quadrature frequency downconverter that has in-phase and quadrature outputs, (b) a first lowpass filter coupled to the in-phase output of the quadrature frequency downconverter, (c) a second lowpass filter coupled to the quadrature output of the quadrature frequency downconverter, and (d) a quadrature frequency upconverter coupled to outputs of the first and second lowpass filters, and wherein a frequency response of each of said first and second lowpass filters has a magnitude that varies approximately with frequency according to a product of raised sin(x)/x functions.