Analog-to-digital converter survey and analysis

Analog-to-digital converters (ADC’s) are ubiquitous, critical components of software radio and other signal processing systems. This paper surveys the state-of-the-art of ADC’s, including experimental converters and commercially available parts. The distribution of resolution versus sampling rate provides insight into ADC performance limitations. At sampling rates below 2 million samples per second (Ms/s), resolution appears to be limited by thermal noise. At sampling rates ranging from 2 Ms/s to 4 giga samples per second (Gs/s), resolution falls off by 1 bit for every doubling of the sampling rate. This behavior may be attributed to uncertainty in the sampling instant due to aperture jitter. For ADC’s operating at multi-Gs/s rates, the speed of the device technology is also a limiting factor due to comparator ambiguity. Many ADC architectures and integrated circuit technologies have been proposed and implemented to push back these limits. The recent trend toward single-chip ADC’s brings lower power dissipation. However, technological progress as measured by the product of the ADC resolution (bits) times the sampling rate is slow. Average improvement is only 1.5 bits for any given sampling frequency over the last six–eight years.