RTD/HBT ANALOG-TO-DIGITAL CONVERTER

INNOVATIVE CIRCUIT DESIGN AND ADVANCED PROCESSING IS PROPOSED TO CREATE A 25 - 50 GS/S, 6- TO 8-BIT ANALOG-TO-DIGITAL CONVERTER (A/D). THE DESIGN COMBINES THE RAPID QUANTUM SWITCHING (< 1 PS) AND MULTIPLE-STATE OPERATION OF RESONANT TUNNEL DIODES (RTD'S) WITH THE ISOLATION, HIGH SPEED (130 GHZ FT), AND FLEXIBILITY OF INP HETEROJUNCTION BIPOLAR TRANSISTORS (HBT'S). THIS COMBINATION, AVAILABLE WITH A STATE-OF-THE-ART PROCESS, ALLOWS Q-DOT TO EXPLOIT THE ADVANTAGES OF BOTH DEVICES. RTD'S HAVE BEEN OPERATED TO 2.5 THZ, BUT THEIR PRACTICAL USE IS LIMITED BY THEIR TWO-TERMINAL NATURE (NO ISOLATION AND LOW DRIVE CAPABILITY). INP HBT'S PROVIDE THE ISOLATION AND DRIVE REQUIRED TO EFFECTIVELY COMBINE FUNCTIONAL BLOCKS, BUT CARE MUST BE TAKEN TO AVOID LIMITING THE RTD'S QUANTUM SWITCHING SPEED. THE PROPOSED DESIGN INTERFACES RTD'S AND HBT'S WITHOUT SERIOUS SPEED DEGRADATION BY USING INNOVATIVE CELL DESIGNS WHICH DO NOT LIMIT RTD SWITCHING SPEEDS. THE A/D DESIGN WILL PRODUCE BOTH ANALOG AND DIGITAL RTD/HBT BUILDING BLOCKS WHICH CAN BE INCORPORATED INTO CELL ARRAYS USEFUL FOR A BROAD RANGE OF APPLICATIONS. DURING PHASE I, MODELLING AND SIMULATION WILL RESULT IN A PRELIMINARY A/D DESIGN WITH ITS PERFORMANCE PROJECTED. FINAL DESIGN, FABRICATION, AND TEST OF A/D PROTOTYPES WILL BE ACCOMPLISHED DURING PHASE II. ANTICIPATED BENEFITS/POTENTIAL APPLICATIONS - X, K, AND MMW RADAR AND COMMUNICATION TRANSMISSIONS CAN BE DIRECTLY CONVERTED BY THE PROPOSED A/D, SUBSTANTIALLY REDUCING FRONT-END COMPLEXITY. CONVERTED DATA CAN BE PROCESSED BY ADVANCED RTD/HBT CELLS. APPLICATIONS TARGETED INCLUDE GPS, HDTV/DBS LINKS, AND PHASED-ARRAY ANTENNA SYSTEMS. THE PROPOSED DESIGN PROVIDES SUBSTANTIAL PERFORMANCE AND FLEXIBILITY INCREASES WHEN COMPARED TO EXISTING DESIGNS.