ON-FOCAL PLANE ANALOG TO DIGITAL CONVERSION

IN ADVANCED INFRARED FOCAL PLANE ARRAYS (IR FPAS), AS THE NUMBER OF DETECTORS ON THE ARRAY INCREASE AND THE COMPLEXITY OF TARGET DETECTIONBECOMES GREATER, THERE IS AN ASTRONOMICAL INCREASE IN SIGNAL PROCESSING NECESSARY TO RESOLVE AND DISCRIMINATE TARGETS SATISFACTORILY. PRE-PROCESSING ON THE FOCAL PLANE TO THE GREATEST EXTENT POSSIBLE IS THEREFORE DESIRABLE, ALTHOUGH IT HAS BEEN LIMITED BY POWER DISSIPATION. THE POWER PROBLEM IS PARTIALLY ADDRESSED BY PERFORMING AS MANY FUNCTIONS AS POSSIBLE IN PARALLEL, WITH ANALOG ELECTRONICS BEHIND EACH DETECTOR. THERE ARE SOME FUNCTIONS THAT CAN BE READILY PERFORMED ONLY DIGITALLY, SUCH AS THRESHOLDING, LONG TERM MEMORY, AND LOGIC. HOWEVER, CURRENT ANALOG TO DIGITAL CONVERTERS (ADC) CONSUME VASTLY MORE POWER THAN CAN BE TOLERATED IN CRYOGENIC IR FPA'S. FEASIBILITY IS BEING EVALUATED OF PERFORMING ON-FOCAL PLANE ANALOG TO DIGITAL CONVERSION FOR LARGE, TWO-DIMENSIONAL IR DETECTOR ARRAYS. A PRELIMINARY ADC DESIGN IS BEING GENERATED AND COMPUTER MODELED TO VERIFY PERFORMANCE WITH INTRINSIC DETECTORS AT LIQUID NITROGEN TEMPERATURES. THE RADIATION HARDNESS OF THE DESIGN IS BEING ANALYTICALLY DEMONSTRATED. THE PRIMARY PERFORMANCE PARAMETERS OF SPEED, RESOLUTION, AND NOISE ARE BEING RELATED TO AREA AND POWER REQUIREMENTS, WHICH WOULD DETERMINE COMPATIBILITY WITH HIGH DENSITY IRARRAYS.