The digital implementation of radio

A class of highly programmable radio architectures is described. Because of distinctly different constraints associated with each propagation environment, compact modular radio frequency (RF) units are needed for each class of radio network to be accessed. These RF units perform the frequency translation of the signals to and from a common high intermediate frequency, which ultimately may be as high as several hundred megahertz. This requires converting between the analog and digital domains at very high sampling rates, which in turn creates some significantly challenging technical problems. Technological issues are discussed in the areas of analog-digital interface and digital up-and-downconversion. An overview of present research and development activity is given