On a wideband fast fourier transform for a radio telescope

Abstract

The radio telescope analyzes a radio frequency from celestial objects by using fast Fourier transform (FFT). In this application, its bandwidth f is wider than that of the typical FFT. Since the amount of hardware for the typical FFT circuit is proportional to the bandwidth f, a special technique is necessary for this application. This paper shows a realization of wideband FFT for the radio telescope on an FPGA. We show that the memory size for the conventional FFT, which consists of the twiddle factor memory and the transpose memory, is too large. We replace the twiddle factor memory with the pipelined CORDIC. To reduce the number of transpose memories, we increase the radix of the FFT from 22 to 2k, also we use the DDR2SDRAM to implement the transpose memory. We implement the 230-FFT on an Altera's Stratix IV GX530 FPGA. It performs the 230-FFT operations in 1.5 seconds. Compared with the Altera's FFT library, our FFT circuit realizes 214 times wider bandwidth on the same FPGA. Also, compared with Tesla S1070 utilizing four GPUs, our FFT circuit is faster and dissipates lower power.