I have tried the following methods to test the orthogonality on Fixed point FFT implementation.
Y = A*x, where A = FFT basis and x = input, Y= FFT output
If the input (x) is set to A-1(A inverse), then the o/p will be an identity matrix. To get A-1(A inverse), first set the input (x) an identity matrix. The output is nothing but the basis vector. Take the transpose and set this as next input, which should give an identity matrix as output.
16bit fixed point implementation, an input value of 1 is set as 0x7FFF, but I was not able to get the orthogonality test by setting this value. Please help me in doing orthogonality test on fixed point FFT implementations.