Sampling/quantization converters

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;
• and
• a processing branch coupled to the input line, said processing branch 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;
• wherein said continuous-time quantization-noise-shaping circuit comprises an adder that includes a plurality of inputs and an output, with the input signal being coupled to one of the inputs of the adder, the output of the adder being coupled to one of the inputs of the adder through a first filter having a first transfer function, and the output of the sampling/quantization circuit being coupled to one of the inputs of the adder through a second filter having a second transfer function,
• wherein the continuous-time quantization-noise-shaping circuit has a noise transfer function with a minimum at a particular frequency,
• wherein a minimum in the quantization-noise transfer function of the quantization-noise-shaping continuous-time circuit corresponds to a frequency band selected by the digital bandpass filter, and
• wherein each of the first transfer function and the second transfer function is at least one of a weighted sum or difference of two filter responses that have group delay and insertion gain that:
• (i) are approximately constant over the frequency band selected by the digital bandpass filter, and (ii) approach zero at frequencies outside the frequency band selected by the digital bandpass filter.