Bandpass delta-sigma data converters

A standard (lowpass) delta-sigma converter uses a sampling frequency which must be many times greater than the highest signal frequency of interest. In contrast, a bandpass delta-sigma data converter needs a sampling rate which is only a few times greater than the highest frequency of interest. Bandpass data converters facilitate high precision analog-to-digital conversion of narrowband bandpass signals in the MHz range. They find application in digital communication systems, spectrum analyzers and special-purpose instrumentation. This paper describes some of the theory behind the technique and summarizes results reported in the literature.