AN 8-BIT SUPERCONDUCTING ANALOG-TO-DIGITAL CONVERTER WITH 10 GHZ INPUT BANDWIDTH

INVESTIGATORS HAVE DEMONSTRATED A 6-BIT A/D CAPABLE OF ABOUT 5 BITS OF RESOLUTION AT 4 GHZ INPUT BANDWIDTH AND ABOUT 4 BITS OF RESOLUTION AT 7 GHZ INPUT BANDWIDTH. THE INPUT BANDWIDTH IS ABOUT 10 GHZ (THE 3DB POINT). HOWEVER, THE RESOLUTION AT GHZ FREQUENCIES IS LIMITED BY DYNAMIC DISTORTIONS IN THE THRESHOLDS PROPORTIONAL TO THE INPUT SIGNAL SLEW RATE. A NEW COMPARATOR DESIGN HAS BEEN SIMULATED IN WHICH THESE DISTORTIONS ARE LARGELY CANCELLED BY SYMMETRY. SIMULATIONS INDICATE AN ORDER OF MAGNITUDE IMPROVEMENT IN THE APERTURE TIME OF THE A/D IF THE PROPER ARCHITECTURE IS USED (ABOUT 3 MORE BITS OF RESOLUTION AT HIGH FREQUENCIES). RESEARCHERS INTEND TO FABRICATE AND TEST THIS DESIGN TO VERIFY THIS LEVEL OF PERFORMANCE AT THE SINGLE COMPARATOR LEVEL.