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Measurements >> RF Measurements >> Phase noise measurement from equipment is USB or DSB?
https://designers-guide.org/forum/YaBB.pl?num=1274422891

Message started by casual on May 20^th, 2010, 11:21pm

Title: Phase noise measurement from equipment is USB or DSB?
Post by casual on May 20^th, 2010, 11:21pm

The default/typical plot from cadence is the USB noise (upper side band), which is 3dB lower than double side band (DSB) phase noise.

typical plot -->(direct plot ->pnoise analysis->function: phase noise)

May I know the measure we get from RF equipments is USB or LSB or DSB??

I am new to RF stuff.

Title: Re: Phase noise measurement from equipment is USB or DSB?
Post by pancho_hideboo on May 21^st, 2010, 3:04am

supermoment wrote on May 20^th, 2010, 11:21pm:

May I know the measure we get from RF equipments is USB or LSB or DSB??

Measurement by spectrum analyzer having simple phase noise measurement option is USB.
Measurement by special equipment is PM noise.

See the followings.
http://www.designers-guide.org/Forum/YaBB.pl?num=1050465395/22#22
http://www.designers-guide.org/Forum/YaBB.pl?num=1256925601/4#4

Title: Re: Phase noise measurement from equipment is USB or DSB?
Post by casual on May 21^st, 2010, 3:44am

a bit confuse after reading the thread.

Per my understanding
1. Phase noise is a combination of PM noise and AM noise. PM noise dominates in close in region (low freq in dBc) while AM noise usually dominates high-freq noise.

2. PM noise can be more than 0dBc in low freq
3. the typical phase noise we got from cadence is USB. (which is already consists of both AM & PM noise, whichever is the worst)
4. spectrum analyzer can measure "output phase noise". However cannot measure PM noise correctly near to low freq. Thus see flat region.
5. Special equipment can do the task (measuring close in noise correctly or PM noise)

Hopefully it is correct :p

Title: Re: Phase noise measurement from equipment is USB or DSB?
Post by pancho_hideboo on May 21^st, 2010, 3:48am

supermoment wrote on May 21^st, 2010, 3:44am:

4. spectrum analyzer can measure "output phase noise". However cannot measure PM noise correctly near to low freq. Thus see flat region.

Not correct.
Simple measurement by Spectrum Analyzer is no more than C/N0.

See http://www.designers-guide.org/Forum/YaBB.pl?num=1241917016

supermoment wrote on May 21^st, 2010, 3:44am:

3. the typical phase noise we got from cadence is USB. (which is already consists of both AM & PM noise, whichever is the worst)

See http://www.designers-guide.org/Forum/YaBB.pl?num=1260521995

supermoment wrote on May 21^st, 2010, 3:44am:

1. Phase noise is a combination of PM noise and AM noise. PM noise dominates in close in region (low freq in dBc) while AM noise usually dominates high-freq noise.

Not correct. It has to be "Normalized Output Sideband Noise".

Title: Re: Phase noise measurement from equipment is USB or DSB?
Post by casual on May 21^st, 2010, 3:59am

I used the wrong word.. correction here:

4. spectrum analyzer can measure "Voltage phase noise" or Sv. However cannot measure PM noise correctly near to low freq. Thus see flat region.

Voltage phase noise = Sv
Phase noise =Sphi (I shall call it: truly phase noise)

refering to http://www.designers-guide.org/Analysis/rf-sim.pdf (pg12)

Title: Re: Phase noise measurement from equipment is USB or DSB?
Post by pancho_hideboo on May 21^st, 2010, 4:01am

supermoment wrote on May 21^st, 2010, 3:59am:

4. spectrum analyzer can measure "Voltage phase noise" or Sv..

Still you are wrong.
It is no more than "Voltage Noise". It is not "Voltage Phase Noise".

Correctly we call it "Sideband Voltage Noise" or "Normalized Sideband Voltage Noise".
Here we don't include any "Phase" term in it.

Title: Re: Phase noise measurement from equipment is USB or DSB?
Post by casual on May 21^st, 2010, 4:21am

ok wrong again

it is called sideband voltage noise=Sv
which consist of both amplitude and phase noise components.

Title: Re: Phase noise measurement from equipment is USB or DSB?
Post by pancho_hideboo on May 21^st, 2010, 4:35am

supermoment wrote on May 21^st, 2010, 4:21am:

it is called sideband voltage noise=Sv
which consist of both amplitude and phase noise components.

Correct.
See http://www.designers-guide.org/Forum/YaBB.pl?num=1050465395/14#14

Title: Re: Phase noise measurement from equipment is USB or DSB?
Post by Mayank on Jun 29^th, 2010, 9:09pm

Also,

Quote:

2. PM noise can be more than 0dBc in low freq

Phase Noise can never be more than 0 dBc coz it means that noise present is more than the carrier itself.
On the other hand, Lphi (which is a small signal approximation of phase noise b/w osc. linewidth & Fosc/2 ) can go above 0 dBc below corner freq.
But true Sphi wont.

As per my understanding, none of the simulators can solve true Sphi correctly for very low frequencies.
What i still wonder is if it's due to lack of proper gaussian flicker noise model in technology models OR is it due to simulator's inability to solve gaussian noise in low-freq. as opposed to Lorentzian after linewidth.

Title: Re: Phase noise measurement from equipment is USB or DSB?
Post by pancho_hideboo on Jul 18^th, 2010, 3:22am

Mayank wrote on Jun 29^th, 2010, 9:09pm:

On the other hand, Lphi (which is a small signal approximation of phase noise b/w osc. linewidth & Fosc/2 ) can go above 0 dBc below corner freq.
But true Sphi wont.

Wrong.

I don't know what you mean by Lphi.
But in actual Measurement using Actual Instruments, L_SSB(f)=C/N0 never go above 0dBc/Hz but S_Φ(f) can go above 0dBrad/Hz.

On the other hand, in simulation using current EDA Tool, L_SSB(f) could go above 0dBc/Hz at low offset especially in the presence of 1/f noise.

Mayank wrote on Jun 29^th, 2010, 9:09pm:

What i still wonder is if it's due to lack of proper gaussian flicker noise model in technology models OR is it due to simulator's inability to solve gaussian noise in low-freq. as opposed to Lorentzian after linewidth.

No.
It is simply due to a limitation of small signal analysis.
See http://www.designers-guide.org/Forum/YaBB.pl?num=1263835149/6#6