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VCO design with -190 dBc/Hz phase noise @ 10 KHz??

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rosaeidi

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noise floor when measuring vco

Hi

My project topic is "Designing a 2.4 GHz VCO with -190 dBc/Hz phase noise @ 10 KHz."

Is it possible?
 

BigBoss

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phase noise dbc hz

Practically impossibe..
How will you measure this ???
 

shogun

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dbc/hz

You might of had a typo and ment -100dBc/Hz at 10kHz offset which is achieveable and reasonable practical depending on your application.

Shogun
 

khach

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Only in liquid helium with superconductive cavity. And -190 is IMHO impossible, only 180-185 because active device noise is degrade cavity performance. Look at the pearametric pumping oscillator with quantum amplifier.
 

Abhishekabs

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-174dBm is thermal noise power at RT for 1Hz bandwidth.
Measurement will be impossible.
I dont think any measuring instrument is available for this kind of measurement.
 

karote

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"-174dBm is thermal noise power at RT for 1Hz bandwidth.
Measurement will be impossible.
I dont think any measuring instrument is available for this kind of measurement."

The original spec was -190dBc/Hz. In case your VCO output power is +16 dBm, you can measure -190dBc/Hz noise level such way that thermal noise does not cause constraints. In practice, there might not be so much instruments that would have over 190 dB dynamic range.
 

Element_115

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Just tell your Prof. that your VCO works to spec and ask him to measure it !
I have never seen any instrument that can measure -190dBc/Hz.
Like others have said before, white noise of our universe is-174dBc/Hz so anything
below that is cutting edge technology. It must be a trick question by your Prof.
 

Ti_W

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Just remember the thermal noise kt/q,about -174dbc/hz at a normal temperature

so I think your project is hard
 

biff44

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A fair bit of misinformation here. -174 dBc/Hz thermal noise floor? Boy is THAT wrong! Check your units.

As far as measuring this, you will need to build two separate oscillators, have some means to phase lock (in a very narrow loop bandwidth) one to the other, put them in quadrature, and beat the two outputs in a mixer (acting as a phase detector). You then video amplify the mixer output and can make your measurement.

As far as actually making the oscillator, you have two choices to TRY:
1) get a very high Q cavity (maybe whispering gallery mode in saphire) and run the oscillator at a very high power level (maybe 1 watt). Look up "Lesson's equation" to see what loaded Q and oscillation power you would need.
2) have a pretty good oscillator, and use a very high Q resonator as a frequency discriminator, and use the frequency discriminator output in a feedback loop to degenerate the original oscillator's phase noise.
 

Nicholaes

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biff44 said:
A fair bit of misinformation here. -174 dBc/Hz thermal noise floor? Boy is THAT wrong! Check your units.

As far as measuring this, you will need to build two separate oscillators, have some means to phase lock (in a very narrow loop bandwidth) one to the other, put them in quadrature, and beat the two outputs in a mixer (acting as a phase detector). You then video amplify the mixer output and can make your measurement.

As far as actually making the oscillator, you have two choices to TRY:
1) get a very high Q cavity (maybe whispering gallery mode in saphire) and run the oscillator at a very high power level (maybe 1 watt). Look up "Lesson's equation" to see what loaded Q and oscillation power you would need.
2) have a pretty good oscillator, and use a very high Q resonator as a frequency discriminator, and use the frequency discriminator output in a feedback loop to degenerate the original oscillator's phase noise.
For single frequency only. Very high Q at 2,4 GHz? For example, if VCO have -105 dBc@10 kHz, your resonator must have 85dB attenuation at 10 kHz offset. So, it's practicaly impossible for single frequency too.
 

BigBoss

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-No measurment equipment has this dynamic range..
190dB !!! ( as I know..)
-Even tough you found a SA (or something else), how this equipment will measure -174dBm/Hz noise level ??

In this area flicker noise is dominant, how this equipment will dicriminate flicker noise from thermal ???

There are too much question..
 

biff44

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Listen, I am not going to hold a school on phase noise measurement techniques or oscillator design. Go do some reading, and stop making such outlandish assumptions about needed dynamic range, or thermal noise floors, etc.
 

Strejda

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Sorry biff44, thermal noise IS 174dBm/Hz.
See - thermal nois is defines as P = kTB where
- k is Boltzman constant (1.38*10^-23 Joules/Kelvin)
- T is Temperature in degrees Kelvin (K= 300 for room temperature)
- B is Bandwidth in Hz

so P = 1.38*10^-23 * 300 * 1 = 4.14 x 10-21 W = -174 dBm


thus, BigBoss has right, period.

Strejda
 

BigBoss

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biff44 said:
Listen, I am not going to hold a school on phase noise measurement techniques or oscillator design. Go do some reading, and stop making such outlandish assumptions about needed dynamic range, or thermal noise floors, etc.

It became too much time from my graduation from the University ( approx 25 years)..
But anyway, if you find a solution to measure -174dBm noise power with standard equipments, we appreciate..
 

Soben

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I am a bit late here, but I will like to comment a bit also.

I hope rosaeidi you have told your supervisor that -190dbc/Hz at 10kHz VCO is out of question except if you invent a new technology of transistors and resonators. And dont lose your time to make the impossible.

However in a DRO I have seen 180-183dBc/Hz at about half of your frequency and 5 times your frequency and it was measured.

As far about the possible measurement of -190dBc/Hz Osc, people forget that the measurement is relative to the carrier power not to the temperature noise floor ( that also can be lowered in a cryogenic environment). The problem right now is that there are no available test equipments for that kind of measurement simple because there are no oscillators around with that kind of specs. However if there is such a low phase noise oscillator, a Phase Lock loop method with Cross correlation will do the trick to lower the noise floor of the measurement equipment to 20-40dB. So far There are Cross correlation measurement systems out there already, but they used to lower the noise floor of their reference internal oscillators only.
 

rfsystem

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-190dBc/Hz


...noise floor is -174dBm so the oscillator power should be >16dBm

but if phase noise does not intercept after 10kHz the noise floor what is the required Q. Is that really a very Q.

around 0dBm with Q=10 gives about -90dBc/Hz at 10KHz so add 16dB for the power and 84dB for the Q from Q=10 ... 10*10^8.4 is a little much...

But ther are some pulse laser experiments giving some fs jitter noise at some MHz repetition ....


need some reading ... later
 

biff44

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Like I said, do some basic research. You will need to amplify the noise floor in an LNA to make the measurement.

It is appalling how people do not seem to know the difference beween dbm/hz and dbc/hz. If you do not understand that, you do not have a prayer of making such a measurement.
 

RFDave

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Take a look at the papers at

https://rubiola.org/

He has some publications that show some impressivly low phase noise performcne, measuring below kTB, but I'm not sure he's gotten below -190 dBc/Hz, as all of his power measurements are in dBm/Hz and dB(rad^2)/Hz

https://arxiv.org/abs/physics/0503015

is a good overview.

Dave
 

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