Proceedings Article | 24 September 2012
Proc. SPIE. 8452, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI
KEYWORDS: Digital signal processing, Clocks, Receivers, Computer programming, Signal processing, Transistors, Analog electronics, Electromagnetic coupling, Digital electronics, Cryogenics
We propose analog-to-digital converters (ADCs) using spread spectrum technology in cryogenic receivers or at warm
room temperature for coherent receiver backend systems. As receiver signals are processed and stored digitally, ADCs
play a critical role in backend read-out systems. To minimize signal distortion, the down-converted signals should be
digitized without further transportation. However, digitizing the signals in or near receivers may cause radio frequency
interference. We suggest that spread spectrum technology can reduce the interference significantly. Moreover, cryogenic
ADCs at regulated temperature in receiver dewars may also increase the bandwidth usage and simplify the backend
digital signal process with fewer temperature-dependant components. While industrial semiconductor technology
continuously reduces transistor power consumption, low power high speed cryogenic ADCs may become a better
solution for coherent receivers. To examine the performance of cooled ADCs, first, we design 4 bit 65 nm and 40 nm
CMOS ADCs specifically at 10 K temperature, which commonly is the second stage temperature in dewars. While the
development of 65 nm and 40 nm CMOS ADCs are still on-going, we estimate the ENOB is 2.4 at 10 GSPS,
corresponding to the correlation efficiency, 0.87. The power consumption is less than 20 mW.
