SiGe Amplifier Technology for High Data Rate Digital Systems

HYPRES, in collaboration with Rennselaer Polytechnic Institute (RPI), proposes to develop a system for amplifying low-level, high-speed digital signals from superconducting electronic components at cryogenic temperatures. This will beaccomplished using high-bandwidth low-noise amplifiers (LNAs) fabricated from silicon-germanium heterojunction bipolar transistors (SiGe HBTs), which can also operate at cryogenic temperatures. This will be demonstrated using a prototype superconductinganalog-to-digital converter (ADC) that generates 1 mV digital signals at speeds up to 3 Gigabits per second. The SiGe amplifier arrays will convert these signals to standard ECL logic levels compatible with conventional electronics. The SiGe LNAs and thesuperconducting ADC will be packaged onto the first stage ( at 65 K) and the second stage (at 4 K) of a commercial closed-cycle refrigerator (cryocooler), together with appropriate high-bandwidth links optimized for this cryogenic system.BENEFITS:Superconducting electronics based on rapid-single-flux-quantum (RSFQ) logic has beendemonstrated to have considerably higher performance, in terms of speed, bandwidth,and sensitivity, than any other integrated circuit technology. This isextremely attractive for a number of Navy applications, including high-resolutionanalog-to-digital converters (ADCs) and fast digital signal processing (DSP)elements for digital receivers for future software-radio communications systems.Since these superconducting circuits work only at cryogenic temperatures of 4-5 K,we must build a link to room temperature to take advantage of these superiorproperties. This is enabled by incorporating cooled SiGe HBT amplifiers at anintermediate temperature. By integrating these together on a compact commercialcryocooler without liquid cryogens, this can be developed into a complete reliableturnkey system where the cryogenics are invisible to the end user, thus enhancingacceptance in the defense and commercial wireless communications markets.