sheldon wrote on Oct 3rd, 2017, 9:02am:Niloun,
Comments:
1) Carl's approach includes an integer number of clock and signal
periods, for example: 13 periods of the signal and 256 periods
of the clock. So, the signals will be periodic in the data record
used for the FFT
2) The reason for using the approach Carl suggest is to assure that
the clock and signal are not harmonically related. For example,
if the clock is 100MHz and the signal is 10MHz, there are only
10 lsb levels tested in the simulation. So the SNDR/SINAD will
be correct, but the SNR and THD will be incorrect. Since all the
energy will be concentrated in 10 bins of the FFT
3) If you follow the guidelines that Carl suggests, you can use the
Rectangular window which means that there is no signal spreading
4) For Delta Sigma, #1 is still applied but you will need to use a
window function
Sheldon
Hi, Sheldon,
It sounds correct to me,
if the clock is 100MHz and the signal is 10MHz, there are only
10 lsb levels tested in the simulation.
So the SNDR/SINAD will
be correct, but the SNR and THD will be incorrect. Since all the
energy will be concentrated in 10 bins of the FFT But why SNDR/SINAN is correct, while SNR/THD not?
Thanks
Feng