Question

I have a radix4 FFT that works in forward direction. How different is the inverse fft from froward? I think the only difference is twiddle factors. My code is a modified version of
Source. Can some one enlighten me on this. Thanks.

My output

1. 50 688
2. -26 -6
3. -10 -16
4. 6.0 -26

Expected output

1. 50 688
2. 6 -26
3. -10 -16
4. -26 -6

Answer 1

Google search “how to compute inverse FFT”. Top result:

http://www.adamsiembida.com/node/23

The equation:

IFFT(X) = 1/N * conj(FFT(conj(X)))

conj() means “complex conjugate”, which basically just means multiplying all the complex values by -1.

http://en.wikipedia.org/wiki/Complex_conjugate