adc in rfic transreceiver

The complexity of modern communication standards requires that operations such as equalization and detection be performed in the digital domain. Furthermore, many functions that were traditionally realized in the analog domain (e.g., channel-selection filtering, frequency offset cancellation, and automatic gain control) can be implemented digitally if baseband A/D converters provide sufficient dynamic range. For these reasons, considerable research effort has been expended on improving the performance of data converters for wireless applications.
With the relative ease of realizing functions digitally, it is desirable to push the analog-to-digital interface toward the antenna. However, both the resolution and the speed required of the ADC must rise, eventually approaching infeasible levels or demanding greater power dissipation than the analog counterparts. The interface has therefore remained at relatively low frequencies, a few tens of megahertz in most cases. The advances in RF and ADC technologies may gradually shift this interface to higher frequencies, but direct digitization at the antenna appears to be an unlikely or nonoptimum solution.