Error due to resolution of data path.On a last paper that i read,
it was written that the desired power spectrum is given from the output of the SD modulator after removing the dc term.
What is the dc term that is mentioned?
Yes........Does it depend on the number of accumulator bits ( N ) or the fractional input?
This plot is a result of dfft() of Cadence OCEAN function.OK so , the first image is the power spectrum as plotted from Cadence Virtuoso.
It seems spectrum results are same between dfft() of Cadence OCEAN function and Scilab ?The second one is the power spectrum ( same configuration as in Virtuoso ), this time plotted in Scilab
There is no DC term in your plot.On a last paper that i read,
it was written that the desired power spectrum is given from the output of the SD modulator after removing the dc term.
What is the dc term that is mentioned?
Your issue has no relation to DC term.but i have an offset of about 20 dB from the ideal curve.
Do you mean this is a result of Z-Domain Transfer function plot ?The third one is the ideal curve, as it is written in the literature.
This plot is a result of dfft() of Cadence OCEAN function.
It seems spectrum results are same between dfft() of Cadence OCEAN function and Scilab ?
What function do you apply in Scilab ?
Even in Cadence OCEAN, two functions exist for evaluating Spectrum, dfft() and psd().
Do you use psd() or dfft() in Scilab ?
Do you mean this is a result of Z-Domain Transfer function plot ?
Still, you can not understand things correctly and also not understand correct terminologies.If i didn't make something clear, please tell me.
fs ; Sampling Frequency
Nfft = 2^17
BinWidth=fs/Nfft
(1) db20( dft() ) - db10(BinWidth) gives dBV/Hz
That one gives an output spectrum that peaks at around -60dB ( yet, as i mentioned above , it changes for longer sampling time )(1) db20( dft() ) - db10(BinWidth) gives dBV/Hz
This one gives almost the same as above, so I guess it is ok.(2) db10( psd() ) gives dBV/Hz
According to the literature, (1-z^-1)^3)^2 expands to (2*sin(pi*f/fs))^6 right?(3) db10( (1/12)/(fs/2)*abs((1-z^-1)^3)^2 ) which gives dBV/Hz
I can not understand what you want to mean at all.For N=14 bits, the full sequence length is Ls=2^(N+1)=15.
I can not understand what you want to mean at all.I And i sample for 2 full Ls, that is 2^16 points.
I can not understand what you want to mean at all.My question is that , if i sample for let's say 16 full Ls, the binWidth according to your formula will be 2^(N+1) * 16= 2^19?
I can not understand what you want to mean at all.that means, there will be difference to the output spectrum if I sample more periods of the periodic signal?
Maybe right.According to the literature, (1-z^-1)^3)^2 expands to (2*sin(pi*f/fs))^6 right?
Rather I don't see such expression.The thing that confuses me is the factor (1/12)/(fs/2).
On almost every paper I came across, this factor is (1/12)/Ls.
Show me your results and fs.If i plot your equation ( in SciLab ),
i get the peak at -80 dB ( big enough difference from the measured data ).
If i plot my variation ( that is substituting fs/2 with Ls ), i get the peak at -40 dB (still 20 dB difference from measured data).
Simply you can not understand basic mathematic especially fft.OK, as it seems i have trouble explaining what i mean
These are for Cadence ViVA using time-domain data.Show me the followings.
fs ; Sampling Frequency
Tstart ; argument for dft()
Tstop ; argument for dft()
Nfft ; argument for dft()
........................................
Show me results of following and setting.
(1) db20( dft() ) - db10(BinWidth)
(2) db10( psd() )
This is for Plot using frequency-domain data in Scilab.Show me your results and fs.
Are your outputs in Spectre truely [-3,4] ?Ok, for all cases N=14 and input 2037 as before.
.................................................
"Cout" is the output carry sequence with range [-3,4] from the 3rd order SD modulator
Show me time domain waveform as a result of Cadence Spectre.Yes they are in the range [-3,4]
Why do you use fs=1GHz ?I am trying to plot the power spectrum of the quantization noise for a MASH topology(for frequency synthesizer)
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