A SUPERCONDUCTING INTEGRATED HIGH RESOLUTION ANALOG-TO- DIGITAL CONVERTER

THE AIM OF THIS PROJECT IS TO DEVELOP AN INTEGRATED ANALOG-TO-DIGITAL (A/D) CONVERTER IN LOW CRITICAL TEMPERATURE (ALL NIOBIUM) SUPERCONDUCTING TECHNOLOGY. THIS A/D CONVERTER IS BASED ON THE JOSEPHSON BINARY COUNTER AND ASINGLE QUANTIZER FRONT END. IT HAS THE POTENTIAL OF ACHIEVING INPUT BANDWIDTH ON THE ORDER OF A FEW TENS OF MHZ AND DYNAMIC RANGE ON THE ORDER OF MORE THAN 12 BITS. IT IS ALSO VERY FLEXIBLE. WITHIN THE MAXIMUM COUNT RATE OF THE BINARY COUNTER, THE SAME DESIGN CAN BE USED TO TRADE OFF THEDYNAMIC RANGE WITH THE INPUT BANDWIDTH. IN ADDITION, THE A/D CONVERTER HAS SUPERIOR LINEARITY LIMITED BY QUANTUM LIMITS, AND IT CAN BE DESIGNED TO HAVE HIGH SENSITIVITY DOWNTO THE SUB-MUA PER LEAST SIGNIFICANT BIT LEVEL. FURTHERMORE, THE INTEGRATED CIRCUIT ITSELF CONSUMES VERY LITTLE POWER, NORMALLY ON THE ORDER OF A FEW MILLIWATTS. THE PHASE I PROJECT SHOULD DEMONSTRATE THE FEASIBILITY OF ACHIEVING WIDE DYNAMIC RANGE WITH THE PRESENT FRONT-END QUANTIZER DESIGN AND QUANTITATIVELY DEMONSTRATE THE DYNAMIC LINEARITY OF THE A/D CONVERTER. THESE DEMONSTRATIONS WILL PERMIT EXPERIMENTAL FEEDBACK ON THE ACHIEVED PERFORMANCE AND LAY THE GROUNDWORK FOR THE PHASE II PROGRAM. IN PHASE II, DESIGN, FABRICATION, AND CHARACTERIZATION OF A HIGH RESOLUTION AND MEDIUM BANDWIDTH A/D CONVERTER WILL BE PERFORMED.