Abstract

The trend in modern communications and radar systems is to move the analog-to digital interface as far forward in the signal path as possible toward the antenna or sensor. Moving the digital interface forward in the signal path eliminates stages of downconversion and analog filtering that are bulky, expensive, drift with temperature, and require calibration. Ultra-fast device technologies are required to perform direct analog-to-digital conversion on radio frequency (RF) or intermediate frequency (IF) signals that enables moving the digital interface forward in the signal path. This paper describes the performance limits of current analog-to-digital converters (ADCs) and shows how the ultra-fast performance of InP HBT technology is extending the performance of ADCs to higher levels to enable all digital approaches to communications receivers.