Digital generation of RF signals for wireless communications with band-pass delta-sigma modulation

This paper demonstrates a high speed digital technique to produce binary (digital) signals that encode representative RF signals (with time varying envelope) as needed for wireless communications. Specifically, it shows that IS-95 format CDMA signals can be generated with a single bit digital data stream at 3.6 Gb/S. The technique uses band-pass delta-sigma modulation so that the quantization noise is shaped out of the frequency band of interest. This approach points the way to single-chip, DSP-based transmitters, used in conjunction with switching mode power amplifiers and simple analog filters, to implement all the functions of a wireless transmitter.