Method

• Move the first input into the centre of the real part of an array X and remove its average. Zero the imaginary part.
• Move the second input into the centre of the real part of an array Y and remove its average. Zero the imaginary part.
• Find the FFT of X and Y, FX and FY
• Compute the FFT of the convolution of FX and FY, FC
• Untransform FC to find the convolution C
• Restore DC level if required and rotate so that zero lag is in the centre of the output