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raymond_luo2003
Joined: 20 May 2004
Posts: 43
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 10 Sep 2004 3:40 phase noise definition |
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Hi,all,
I am tatally confused by the definition of Phase noise.
I have seen a lot of different TERMs for phase noise definition
1) Phase Noise
2) Spectral Density
3) Power Spectral Density
4) Spectrum
5) Single side band power spectral density
6) Auto-correlation function
It seems that they all different but related!! Who has very clear reference on that? Very appreciate if any can share your understanding and reference!!
Thanks!
Raymond
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brmadhukar
Joined: 21 Jun 2002
Posts: 844
Helped: 29
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| 10 Sep 2004 15:43 Re: phase noise definition |
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Hi,
Phase noise basically measures the error in frequency. Normally any frequency output is not really stable and error free. The true output will be distributed around the nominal and less the distribution better the source and it is more expensive to get the same.
The phase noise normally measured by the amplitude and range of the spread.
B R M
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DoctorX
Joined: 02 Sep 2004
Posts: 73
Location: USA
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| 11 Sep 2004 3:44 Re: phase noise definition |
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| raymond_luo2003 wrote: |
Hi,all,
1) Phase Noise
2) Spectral Density
3) Power Spectral Density
4) Spectrum
5) Single side band power spectral density
6) Auto-correlation function
It seems that they all different but related!! Who has very clear reference on that? Very appreciate if any can share your understanding and reference!!
Raymond |
Phase noise is in fact the random frequency fluctuation observed in real oscillators. As the frequency fluctuation is normally small and centered around 0, we may take its integration, which is phase, as a random process to study.
When phase noise is treated as a (typically wide-sense stationary) random process, it is best characterized by its time-domain self-correlation function. If you take the Fourier transformation of the correlation function, you get a power spectrum, which is what you see in publications.
As a spectrum plot is hard to describe verbally, typically phase noise is quantized by xxx dBc at xxx offset. Such as -110 dBc at 1 MHz offset, with center frequency at 5.2 GHz, it means that at 5.201 or 5.199 GHz, the power spectrum density of phase noise is 110 dB BELOW the power of fundamental (desired) signal.
By default the phase noise (power) spectrum is expressed in double-sideband format, as F0 >> 0, say = 5.2 GHz. However, in some cases, such as direct down conversion reception, one of the two sidebands is folded back and overlaps the other, so the power adds up. Hence, sometimes single-sideband phase noise is more convenient.
Anybody has some thought over the calculation of phase noise for simple (analog, not ring) oscillators?
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DoctorX
Joined: 02 Sep 2004
Posts: 73
Location: USA
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| 11 Sep 2004 3:48 Re: phase noise definition |
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Random process and power spectrum density summary.
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djalli
Joined: 10 Nov 2001
Posts: 887
Helped: 15
Location: 1600 Pennsylvania Avenue, Washington DC 20500
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| 11 Sep 2004 4:29 phase noise definition |
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Suppose we have a signal going into a certain circuit, an AND gate for sake of simplicity.
If a signal going into a circuit will be delayed eventually, so signal out will lag in phase with input signal. Let say for 20Hz signal lags 5 degrees.
Now suppose you have another signal for 10Hz and lags 2.5degrees
and a third signals of 12 Hz lagging 24degrees (delayed).
This amount of lagging (actually difference) is what is in most of times a phase noise attached to the signal.
Just try to picture it this way at least in most basic form of imagination
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DoctorX
Joined: 02 Sep 2004
Posts: 73
Location: USA
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| 15 Sep 2004 22:32 Re: phase noise definition |
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| djalli wrote: |
Suppose we have a signal going into a certain circuit, an AND gate for sake of simplicity.
If a signal going into a circuit will be delayed eventually, so signal out will lag in phase with input signal. Let say for 20Hz signal lags 5 degrees.
Now suppose you have another signal for 10Hz and lags 2.5degrees
and a third signals of 12 Hz lagging 24degrees (delayed).
This amount of lagging (actually difference) is what is in most of times a phase noise attached to the signal.
Just try to picture it this way at least in most basic form of imagination |
This appears to me is the definition of distortionless signal propagating -- linear phase. However, the addition of phase noise when the clock signal passes some circuitry is due to the UNEVEN (fluctuating) addition of extra phase.
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frannk
Joined: 22 Jul 2004
Posts: 66
Helped: 3
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| 15 Sep 2004 22:46 Re: phase noise definition |
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goto:
http://eeclass.stanford.edu/ee314/
select 'handouts', then 'general handouts'.
there's a tutorial on phase noise by Thomas Lee of Stanford University
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