My design is 4096-point FFT, which splits into 4 stages of radix-8 FFT. The system twiddle factor is 15-bits and gives acceptable quantization error. However the design is bogged down by the trivial twiddle factor within radix-8, W81 = 2 * pi * 1/8 = 0.707, which can be reasonably done with 181/256. However the quantization of 181/256 causes system quantization error from 80dB to 30+dB, and this error absorbed quantization error variations with system twiddle factors varying between 13~20bits. Consideration is the system memory (4096 point, 13b) won't be widdened to accomodate this 0.707. Are there any means to fix this problem?
How would one minimize quantization error in radix-8 based FFT?
Started by ●February 7, 2007