Performance and area tradeoffs in space-qualified FPGA-based time-of-flight systems

This paper introduces four FPGA-based designs for radiation-tolerant time-of-flight (TOF) systems for sub-atomic particles: Snapshot, Vernier, Fast-Clocking and Hybrid designs. The designs measure TOFs ranging from 0 to 240 ns and are compared based on resolution, thermal performance, FPGA I/O pin usage and area, particle processing rate, and power consumption. All designs are implemented and tested on an Actel ProASIC 3E A3PE1500 FPGA using only the features available on the radiation-tolerant Actel RTAX 2000 S/SL. The designs achieve resolutions of 130 ps to 25 ns and particle rates of 1.63 to 40 MHz, use from 0.02% to 7.5% of the FPGA area, and consume from 396 to 448 mW. The TOF measurements of the fast-clocking design show no thermal variation across the ranges of -25degC to 55degC. The other three designs vary linearly with temperature, but this variation can be calibrated using a temperature sensor. All four designs offer a flexible, inexpensive TOF measurement system that can be implemented across a broad range of FPGAs.