DPOJET phase noise

I'd like to know more about how do you calculate the phase noise in DPOJET tool box? is it FFT of TIE jitter sequence?

and if my input clock is 1Mhz, how to set noise integration limits (upper/lower frequency)? shall i set the upper frequency = 1MHz/2?
is it the integrated bandwidth in which total TIE jitter power put in?

thanks
Jeff
 

The DPOJET help manual states:

"The Phase Noise measurement performs a jitter measurement, converts the result into the frequency domain, and reports
the rms jitter integrated between two specific frequencies selected by the user."

So a TIE jitter measurement is performed and an FFT is conducted of that.

The integration limits that are used depends on what the user wants to see, which is generally based on the specification for the clock.

Hi. 
Thanks.
As to the integration limits, i guess you are saying that the clock frequency (half of it) defines the upper limit, right? if user inputs a higher upper freq, it will get ignored?
by the way, the unit of phase noise is wrong in DPOJET, it's lablled by dBc/sqrt(Hz) instead of dBc/Hz. 

regards
JEFF 

HI
Can any one tell me what is RWB of jitter spectrum? if my scope sampling freq. is 1.56gHZ and record length is 31.25M.

Thnanks
jeff

Hi Yan,
IMHO (but please double check it is Friday and Beer Time here 8PM)
The TIE Time Interval Error Jitter Trend is sampled by your actual measured signal.
your Jitter FFT Max Frequency will be 1MHz/2
your Jitter FFT Min Frequency will be 1/(RecordLength*SamplingRate)
your Jitter FFT number of points should be half of number of TIE samples (here this should equate to 1E6x(RecordLength*SamplingRate)

your Jitter FFT RBW should be (FFT_Max_Frequency-FFT_Min_Frequency)/FFT_Number_of_Points
Jitter FFT RBW=(FFT_Max_Frequency-FFT_Min_Frequency)/(1.56e9x(RecordLength*SamplingRate)

Now regarding the phase noise plot (assumptions here)
I have run the PhaseNoise Plot with your settings on my scope, then I saved the PhaseNois ePLot as .mat file

then I opened it insid eMatlab
dataphasenoise=load('D:\DOCUMENTS\Phase Noise\Phase Noise 1MHz Sinawave 1.56GSas.mat');

then I digged inside it:
dataphasenoise.DPOJET.Plot.line

ans = 

  struct with fields:

              XData: [50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 … ]
              YData: [-99.8782 -97.3776 -96.4661 -96.6948 -102.6597 -101.1378 -102.5144 -105.3665 -102.7922 … ]
              ZData: [1×0 double]
              Color: [1 0.5000 0]
          LineStyle: '-'
          LineWidth: 0.5000
             Marker: 'none'
         MarkerSize: 6
    MarkerEdgeColor: 'auto'
    MarkerFaceColor: 'none'
                Tag: 'Spectrum'

Looking at XDATA so it seems that RBW is 50Hz

Have a great weekend!
Kind regards
Pascal


 

hi Pascal,

thanks for the reply.

do you think there would be no FFT window applied?

if no window applied , fft min freq = fs/rec. length = 1/capture time.

it yes, what kind of window used, do you know?

regards

jeff 

I'm trying to set up the DPOJET to do a TIE jitter analysis on  a differential manchester encoded/ biphase mark encoded signal. Is there a way to configure the clock recovery so that it doesn't see the different types of transitions as jitter.