ABSTRACT
This chapter introduces a new transmitter architecture that targets high data rate wideband systems. Sigma–delta digital–RF modulation efficiently modulates a radiofrequency (RF) carrier with very wide bandwidths by replacing high dynamic range analog circuits with high-speed digital circuits. This technique enables power and area savings in the implementation of a wideband transmitter as complementary metal oxide semiconductor (CMOS) transistors continue scaling. As CMOS technology continues to scale, and wireless system bandwidths increase, direct digital–RF modulation will become more attractive. By modulating an entire band of spectrum with sufficient dynamic range, a wideband digital–RF modulator can transmit any number of channels within the band using varying bandwidths and modulation schemes. In this way, the transmitter can be configured to utilize and share spectrum in a certain band on an adaptive basis, depending upon channel conditions, spectrum availability, and the presence of interferers from other systems.
