A DSP-based alternative to direct conversion receivers for digital mobile communications

The authors describe a digital conversion receiver featuring digitization at a low IF (intermediate frequency), followed by DSP (digital signal processing)-based extraction of the complex envelope components. It eliminates the problems of DC offset and phase and gain imbalance encountered in analog direct conversion designs. The sensitivity of the digital conversion receiver is comparable to that of other designs, and its dynamic range is determined by the analog IF amplifier rather than by the A/D (analog-to-digital) converter and DSP. A model for the bandpass A/D converter that can be included in conventional receiver design calculations is also presented