Patent ID: 7860189

Claim:
A complex sigma-delta analog-to-digital converter (ADC), constructed and arranged to receive a continuous time modulated analog input signal at an RF carrier frequency and provide a quantized output at an intermediate frequency (IF), the complex sigma-delta ADC comprising: a first summing node responsive to the modulated analog input signal at the RF carrier frequency and a first feedback signal comprising an analog replica of a quantized output of the sigma-delta ADC, wherein the summing node produces a first error signal at an RF carrier frequency; a bandpass filter providing first noise-shaping responsive to the first error signal at the RF carrier frequency and the first feedback signal comprising a first analog replica of the quantized output, wherein the bandpass filter provides at least one pole in a frequency band that includes the RF carrier frequency; an analog mixer mixing the first error signal after first noise-shaping with a first mixing frequency offset from the RF carrier frequency by an intermediate frequency (IF), wherein the mixer generates a frequency shifted first error signal at the IF; a complex filter providing complex noise-shaping of the frequency shifted first error signal at the IF, the complex filter responsive to a second feedback signal comprising a second analog replica of the quantized output, wherein the complex noise-shaping filter provides at least one pole in a frequency band that includes the IF; and a quantizer receiving the noise-shaped frequency shifted first error signal at the IF after complex noise-shaping and providing a quantized sigma-delta ADC output.