Assessing Multicarrier Direct-Conversion Transmitters

摘要

Careful component selection can make direct-conversion architectures practical for multicarrier WCDMA and CDMA2000 cellular base stations. Direct-conversion transmitters appeal to designers of wireless systems for their simplicity and low cost. Unfortunately, the simple architecture does not allow the filtering of broadband noise, images and spurious components typically executed at intermediate frequencies (IFs) in a more complex superheterodyne transmitter. For designers to migrate single-carrier base stations to multicarrier architectures using direct-conversion approaches, they must use components with high output compression and low noise. What follows is an examination of the direct-conversion approach for multicarrier WCDMA and CDMA2000, with particular attention on that critical component, the inphase/quadrature (I/Q) modulator.