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JC

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How to use phaseNoise() function in OCEAN script?
Apr 08^th, 2007, 4:39am

I used the function "plot(phaseNoise(1 "pss_fd" ?result "pnoise"))" to plot the phase noise figure, but I don't know the meaning of the first argument in the function "phaseNoise( )".

The definition says the first argument is "g_harmonic --- List of harmonic frequencies." What does this mean? When I change its value, the phase noise figures have the same shape but different values.

===========The definition of function phaseNoise( ) in OCEAN document==================
phaseNoise( g_harmonic S_signalResultName [?result s_noiseResultName [?resultsDir t_resultsDir]] )

g_harmonic List of harmonic frequencies.
S_signalResultName Name of the result that stores the signal waveform. Use the
results() command to obtain the list results.
.............

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Ken Kundert

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Re: How to use phaseNoise() function in OCEAN scri
Reply #1 - Apr 8^th, 2007, 7:51am

If you have a 1GHz oscillator, then using 1 will give you the phase noise about the first harmonic, or the one at 1GHz. Specifying 2 would give you the phase noise about the 2nd harmonic, or the one at 2GHz. This is primarily used when your circuit contains a frequency divider. For example, if you had a divide by 2 with your 1GHz oscillator, the fundamental frequency for the analysis would be 500MHz, and the oscillator output frequency would be at the 2nd harmonic of 500MHz, so you would use 2 when observing the phase noise at the output of the oscillator.

-Ken

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JC

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Re: How to use phaseNoise() function in OCEAN scri
Reply #2 - Apr 8^th, 2007, 8:32am

Thanks for your reply!

You mean if I have a 1GHz oscillator, then using 1 I will get the phase noise about the first harmonic �(1GHz) and using 2 about the 2nd harmonic (2Ghz). In my understanding phase noise about �the 2nd harmonic (2Ghz) should be smaller than that of the first harmonic �(1GHz). �I don't know whether is it right? confusing.....

Howerver, when I plot two figures (one using 1 and the other using 2) together, I found phase noise about �the 2nd harmonic (2Ghz) is bigger than that of the first harmonic �(1GHz) . The functions are "plot(phaseNoise(1 "pss_fd" ?result "pnoise"))" and "plot(phaseNoise(2 "pss_fd" ?result "pnoise"))".

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ACWWong

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Re: How to use phaseNoise() function in OCEAN scri
Reply #3 - Apr 8^th, 2007, 2:43pm

the phase noise plotted is dBc/Hz (decibel from carrier per Hertz) so is in reference to some carrier level.

when the reference harmonic is 1 (lets say this the oscillator frequency= 1GHz), then you get the phase noise in dBc/Hz with reference to the fundamental "carrier" signal level at 1GHz.

when you do the phase noise with reference to harmonic 2, indeed your dBc/Hz phase noise plot may look like its bigger, but this is because you are now referencing a carrier level at 2GHz (which in your case is probably very small compared to the fundamental carrier at 1GHz). You can check the difference in the levels between the carrier references at 1GHz (harmonic 1) or 2GHz (harminic 2), by looking at your pss results.

see this related topic below to help further your understanding, where here now the refernce harmonic for the phase noise plot is fixed, but the sweep pnoise sweep goes past the 2nd harmonic:
http://www.designers-guide.org/Forum/YaBB.pl?num=1174556880

cheers
aw

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JC

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Re: How to use phaseNoise() function in OCEAN scri
Reply #4 - Apr 9^th, 2007, 9:14am

Thanks for you reply!
I am more clearly right now. However, I am still confusing about how to calculating phase noise. According to the difinition phase noise is that "the noise power in a unit bandwidth at an offset w0 with respect to carrier wc and then divided by the carrier (average) power in log scale" --- from Razavi's RF microelectronics.

How to calculate the phase noise if I get a output signal spectrum as follows Fig. 1?

I know how to calculate the noise power in a unit bandwidth, but how about the carrier (average) power. Is it just the power of the harmonic at 1GHz (in my case) or include all frequency components which distribute the whole spectrum? �

If the carrier (average) power is the power of harmonic at 1GHz, it is positive proportional to the square of amplituds of the first harmonic (1GHz), i.e. A² (Fig.1). If the carrier (average) power includes the power of all frequency components, it is the integral of the square of output signal's spectrum. Correct?

Best regards!

-JC

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Phase_noise_cal_001.JPG

« Last Edit: Apr 9^th, 2007, 10:36am by JC »

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ACWWong Community Fellow Offline Posts: 539 Oxford, UK	Re: How to use phaseNoise() function in OCEAN scri Reply #5 - Apr 9^th, 2007, 10:57am as far as i am aware, you use A² if A is voltage... but this is usually taken into account by using 20*log(Vsignalrms)...
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JC Junior Member Offline Posts: 23	Re: How to use phaseNoise() function in OCEAN scri Reply #6 - Apr 10^th, 2007, 3:03pm Thanks for all of you! :D -JC
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