HdrChopper wrote on May 23rd, 2009, 8:34pm:However if you are also processing noise applying just a simple fft(x) will not give you accurate results.
It will work ok if your signal is deterministic though.
It is true theoretically.
But I don't think so from practical point of view.
A simple abs(fft(x))
2 is a approximation of true PSD, here approximation point is lack of ensemble averaging.
I think a simple abs(fft(x))
2 is enough useful even for random signal(stochastic signal).
I can get following well known PSD value in Transient Noise Analysis even with simple abs(fft(x))
2.
PSD=k*T=-173.8[dBm/Hz], k=1.38*10
-23[J/K], T=300[K]
In the following, band limited white gaussian noises are added in system and I evaluate ACPR by using simple abs(fft(x))
2.
http://www.designers-guide.org/Forum/YaBB.pl?num=1190971685/7#7Do you truely evaluate PSD based on a Spectrum of auto-correlation function for results of Transient Noise Analysis ?, although it might be dependent on purpose of PSD.
In audio signal analysis, PSD based on a Spectrum of auto-correlation function is used exclusively.
Even if we use Spectrum of auto-correlation function as PSD for practical finite length time sequence {x[n]}, it is also no more than approximation of true PSD.