Question

How many number of bits are required to compute the FFT of a 1024 point sequence with a SNR of 30db?

(a) 11

(b) 10

(c) 5

(d) 20

I got this question in unit test.

Question is taken from Quantization Effects in the Computation of DFT topic in portion DFT Efficient Computation – Fast Fourier Transform Algorithms of Digital Signal Processing

Answer 1

Correct choice is (a) 11

Explanation: The size of the FFT is N=2^10. Hence the SNR is 10 log102^2b-v-1=30

=>3(2b-11)=30

=>b=21/2=11 bits.