Bandpass implementation of the sigma-delta A-D conversion technique

A new design of band-pass sigma-delta A-D converter is presented which can encode the signal at the intermediate frequency and then by digital post processing convert to baseband I and Q. The technique of band-pass sigma-delta conversion is described and a method for designing band-pass A-D converters from existing baseband modulator designs is given with an example to illustrate the theory. Practical results are described with the performance specified in conventional RF circuit terms