Bandpass delta-sigma modulators for direct IF and RF sampling digital receivers implemented in InP HBT IC technology

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 filters that are bulky, expensive, require calibration, and drift with temperature. 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 use of ultra-fast InP HBT IC technology to build bandpass delta-sigma modulators for use in IF sampling digital receivers