MONOLITHIC GAAS DIGITIZER FOR SPACE-BASE LASER ALTIMETER PULSE-SPREADING EFFECT

A MINIATURE, LOW-POWER, GAAS MONOLITHIC GHZ WAVEFORM DIGITIZER IS PROPOSED FOR ANALYZINGSPACE-BASE LASER ALTIMETER PULSE-SPREADING EFFECT. IT CONSISTS OF A GHZ GAASSAMPLE-AND-HOLD AND A 6-BIT MONOLITHIC GAAS FLASH A/D CONVERTER USING THE ENHANCEMENT/DEPLETION (E/D) TECHNOLOGY AND LATCHING COMPARATORS. THE ADVANTAGES OF THE APPROACH ARE: (1) THE USE OF A FRONT-END SAMPLE-AND-HOLD ELIMINATES THE CLOCK-INDUCED TRANSIENT NOISE PROBLEM ASSOCIATED WITH THE COMPARATORS AND (2) IT ENABLES SMALLER DEVICES TO BE USED FOR THE COMPARATORS TO SAVE POWER WITHOUT SACRIFICING THE INPUT BANDWIDTH. THE E/D GAAS TECHNOLOGY WILL MINIMIZE THE POWER CONSUMPTIONS OF THE 6-BIT A/D CONVERTER TO 400MW. THE E/D LATCHING COMPARATORS PROVIDE HIGH GAIN AND REDUCE THE COMPARATOR OFF-SET VOLTAGE DOWN TO 15 MV, THUS MAKING THE 6-BIT DYNAMIC RANGE RELIZABLE.