Phase Noise and Jitter Measurements - The Designer's Guide Community Forum
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Phase Noise and Jitter Measurements - The Designer's Guide Community Forumen-usThe Designer's Guide Community ForumTue, 17 May 2022 08:22:42 +0000http://blogs.law.harvard.edu/tech/rss30Phase Noise through the NTF of VCO
https://designers-guide.org/forum/YaBB.pl?num=1634826957
The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1634826957Assuming that I have a PSD of random noise on Vcontrol of VCO as discrete points from the simulator, eg. 50 points per decade. Now I have to simply find the phase noise at the output of the VCO. Do I :<br />A. assume the NTF is Kvco/f, do dot product of PSD and square(Kvco/f) at the corresponding frequency points?<br /> OR<br />B. Now that the points are discrete, I assume each bin value is a sinusoid, convert the rms to peak by sqrt(2) and then get the USB/LSB as half the value and then dot product by square(Kvco/f) at the corresponding frequency points?<br /><br />A and B differ by a scaling factor due to the sinusoid assumption.VCO Phase Noise Modeling using Verilog-A, Verilog-AMS
https://designers-guide.org/forum/YaBB.pl?num=1582082899
The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1582082899If you can assume the noise is dominated by white noise, then you can actually make the vco model in verilogAMS by deriving period jitter from it. Now given that the noise at an offset is known, the curve is completely defined in all the points or in other words you can find out the N=H(f) of the noise. Assuming that you need the period jitter, multiply it by a (1-zinv) filter and integrate the noise. This is the sigma of each period. Now you find a random number in your code based on this sigma and pass it to the oscillator. It will generate an integrated noise which corresponds to the PSD of your actual oscillator. Da Dalt's book on understanding jitter has details on retrieving period jitter from spot noise of purely 1/f^2 noise.<br /><br />You can even model flicker noise by using multirate filters to create 10dB/decade which is explained in Staszewski's book. But it can be a next step.Simulation to retrieve reference spur
https://designers-guide.org/forum/YaBB.pl?num=1620755917
The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1620755917Hi,<br />Regarding how to calculate the reference spur analytically is available everywhere. Could anyone suggest a methodology for simulating and measuring the reference spur for a charge Pump that has a pre determined static phase offset. Assume the LF to be the standard C1, R, C2 type.(Multi-modulus) divider phase noise simulation
https://designers-guide.org/forum/YaBB.pl?num=1603971413
The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1603971413Hello everyone,<br />Sorry if I missed the topic and the question is already answered.<br /><br />I want to simulate the phase noise contribution of an MMD used in a frequency synthesizer. For the purpose of simulation, the division is integer ( divide by N ). I use PSS and add Beat frequency to be Fvco/N ( where Fvco is the vco output frequency ). <br />Also i add harmonics to be 5*N ( that would equal to 5 harmonics of Fvco).<br /><br />Then in Pnoise simulation , I use 10 maximum sidebands and add the voltage nodes I am interested in ( output nodes of MMD ). Im measuring relative harmonic 1 also.<br /><br />Is this the correct way to simulate a divider or am I missing something?<br /><br />Thank you in advancePhase Noise of Squared Noisy Sine Wave (Ian Galton's Paper)
https://designers-guide.org/forum/YaBB.pl?num=1603949787
The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1603949787I have read [I. Galton 2018] and wanted to understand the effect of <i>squaring </i> deeply. I made a simple experiment to observe the effect of squaring, but I am unable to make sense of the results.<br /><br /><b>MATLAB experiment description:</b> I have taken a sine wave of frequency 100MHz, sampled at the rate 100GHz. To this sine wave, I have added a sinusoidal phase noise of magnitude "alpha" and frequency 10MHz. When I take the FFT of the resultant signal, I get the expected frequency spectrum.<br /><br /> <b>Code:</b><pre class="code" style="margin: 0px; width: 90%; overflow: auto;">clear all
close all;
f0 = 100e6;
df = 10e6;
tTotal= 1e-6;
Fs = 100e9;
Ts = 1/Fs;
t = 0:Ts:tTotal-Ts;
alpha = 1e-6;
a = sin(2*pi*f0*t + alpha*sin(2*pi*df*t)) ;
afft = fft(a)/length(a);
afftdb = 20*log10(abs(afft)+1e-8);
figure(1)
plot(afftdb);
</pre><br /><br /> <img src="https://i.stack.imgur.com/dHyUpm.png" alt="" border="0" /><br /><br />The strength of the spur at bin 111 is 20log(alpha/2) relative to the carrier as expected. Next, I have converted this sine wave into a squarewave, then hann-windowed, then low pass filtered and finally I've taken the FFT.<br /><br /> <b>Code:</b><pre class="code" style="margin: 0px; width: 90%; overflow: auto;">asquare = sign(a);
y = lowpass(asquare,200e6,Fs,'ImpulseResponse','iir','Steepness',0.95);
win = 0.5*(1-cos(2*pi*t/tTotal));
y =y.*win;
%asq_fft = fft(asquare)/length(a);
asq_fft = fft(y)/length(a);
asq_fftdB = 20*log10(abs(asq_fft)+1e-8);
figure(2)
plot(asq_fftdB)
</pre><br /><br />I get spur of strength -64dB which is unexpected for me (see below image). I didn't expect to get this high spur. I expected the spur to still be 20log(alpha/2) relative to the carrier. I also don't understand why I get so many harmonics too.<br /><br /> <img src="https://i.stack.imgur.com/geiK9m.jpg" alt="" border="0" /><br /><br />I also tried changing the value of alpha from 1e-6 to 1e-11. The FFT plot for alpha of 1e-11 is given below:<br /><br /> <img src="https://i.stack.imgur.com/geiK9m.jpg" alt="" border="0" /><br /><br />Still, the strength of the spur didn't change. This is surprising to me. Could anyone please explain why does the spur's strength of -64dB make sense?<br />When I make alpha = 0, there are no spurs. So, there is no FFT leakage issue here. <br /><br />[I. Galton 2018] I. Galton and C. Weltin-Wu, "Understanding Phase Error and Jitter: Definitions, Implications, Simulations, and Measurement," in IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 66, no. 1, pp. 1-19, Jan. 2019, doi: 10.1109/TCSI.2018.2856247.<br />Discrepancy between PSD of matlab script and PSD of Spectre
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The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1602269884Hi Ken:<br /><br />Thanks for your prompt comments. Your insight gives me some hint that the issue might be caused from the different/inaccurate phase crossing points that the PSD relies on.<br />I will do some further investigation. Thanks anyway.Confusion with the terminology "RMS jitter" in papers. Is it Jc or Jee?
https://designers-guide.org/forum/YaBB.pl?num=1601481739
The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1601481739Greetings,<br />While doing literature survey [1] and [2], I found that the authors have used the word "rms jitter" to report their jitter numbers. I am confused whether they mean cycle jitter (Jc) or edge-to-edge jitter (Jee) since both of them are jitter and are rms quantities. <br />Could you please tell me which jitter are they refering to? <br /><br />P.S. I know what each term mean.<br /><br />[1] A. Elkholy et al., "15.4 A 20-to-1000MHz ±14ps peak-to-peak jitter reconfigurable multi-output all-digital clock generator using open-loop fractional dividers in 65nm CMOS," 2014 IEEE International Solid-State Circuits Conference Digest of Technical Papers (ISSCC)<br /><br />[2] S. Hung and S. Pamarti, "6.4 A 0.5-to-2.5GHz Multi-Output Fractional Frequency Synthesizer with 90fs Jitter and -106dBc Spurious Tones Based on Digital Spur Cancellation," 2019 IEEE International Solid- State Circuits ConferencePhase noise and SFDR measurement of a Digital to Frequency Converter
https://designers-guide.org/forum/YaBB.pl?num=1597951085
The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1597951085Thank you so much Ken!!! jitter measurement for phase domain model PLL
https://designers-guide.org/forum/YaBB.pl?num=1597853375
The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1597853375I don't know. I am not that familiar with the calculator. Conceptually the flicker noise has a -10dB/dec slope and the white noise is flat. The corner frequency is where the asymptotes for these two regions intersect.<br /><br />-Kenphase.vams
https://designers-guide.org/forum/YaBB.pl?num=1582572832
The Designer's Guide Community Forum/Phase Noise and Jitter Measurementshttps://designers-guide.org/forum/YaBB.pl?num=1582572832I just realised that Listing 2 is from <a href="https://designers-guide.org/analysis/PLLnoise+jitter.pdf" target="_blank">https://designers-guide.org/analysis/PLLnoise+jitter.pdf</a> - with the definition there, the code also compiles with Spectre 18.1 and 19.1 (unsurprisingly since the discipline is essentially similar to the standard rotational).<br /><br />Andrew.