Signal processing at 250 MHz using high-performance FPGA's

This paper describes an application in high-performance signal processing using reconfigurable computing engines: a 250 MHz cross correlator for radio astronomy. Experimental results indicate that complementary metal-oxide-semiconductor (CMOS) field programmable gate arrays (FPGA's) can perform useful computation at 250 MHz. The notion of an "event horizon" for FPGA's leads to clear design constraints for high-speed application developers, and can be applied to a variety of real-time signal processing algorithms. Recent estimates indicate that higher performance FPGA's available early in 1998 can attain speeds of over 300 MHz using 20% fewer logic elements than current designs. The results of this design work provide important clues on how to improve FPGA architectures for signal processing at hundreds of MHz. Direct routing channels between logic elements can significantly increase performance. Routing architectures with four-way symmetry allow for rotations and reflections of subcircuits needed for optimal packing density. Experimental results indicate that clock buffering often limits the top speed of the FPGA. Wave pipelining of the clock distribution network may improve FPGA performance.