Hello,
I would like to find spectrum power based on 16-bit 1024-size IQ samples.. In time domain I find the right answer, but in spectrum I can't. I think it is because of scaling factor, which I couldn't understand what value to use of. Please help me out on this..
Here is how i find FFT..
#define N 1024
#pragma DATA_ALIGN(wfft, 8);
float wfft [N];
#pragma DATA_ALIGN(iq_sample, 8);
float iq_sample [2*N];
short table[N];
float fft_mag[N];
...
...
...
bitrev_index(table,N);
gen_twiddle(wfft,N);
bit_rev(wfft, N>>1);
DSPF_sp_cfftr2_dit(iq_sample, wfft, N);
DSPF_sp_bitrev_cplx((double*)iq_sample, table, N);
i =0;
for(; i<N; i++)
{
fft_mag[i] = iq_sample[2*i]*iq_sample[2*i]+iq_sample[2*i+1]*iq_sample[2*i+1];
totalpower += fft_mag[i];
}
totalpower = 10 * log10(totalpower);
Note: I found a code somewhere on the web, it takes scaling factor as 0.00065, which gives almost what i'm looking for.. But, where does this value come from?
Thanks a lot..
