Direct conversion using lowpass sigma-delta modulation

A method for quadrature demodulation by subsampling with sigma-delta analog-to-digital converters is discussed, and a correlator receiver structure based on this method is described. The almost completely digital demodulator structure is based on second-order sampling and sigma-delta analog-to-digital converters. A theoretical performance analysis is presented, and a measurement system for the method is described. The proposed structure can be implemented on a single integrated circuit.<
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