Hi Guys
 I had a measured results shows the following spectrum of ring oscillator, it seems the spectrum is dirty, any suggestions what the phase noise source might be?  I do not think it is flicker noise since it is at the 10Mhz region, am I right? Also, is their paper or post about VCO layout techniques? I would like to make a PLL, but I want to isolate VCO from mixer and amplifier stage if possible.
 Thanks

pancho_hideboo wrote on May 4^th, 2009, 8:53am:

Can you explain more free running state?
In which state it will be better spectrum?
 how yo measure envelope_amplitude v.s. time ?
 Frequency Deviation v.s. time ?
 what's the use of it?
 I use agilent spectrum analysizer to measure it and GSG probe.

pancho_hideboo wrote on May 4^th, 2009, 9:11am:
It is "not locked state".
so for unlocked state, the spectrum is very dirty?
liletian wrote on May 4^th, 2009, 9:05am:
You don't seem to understand VCO, PLL, etc.
I do, I read a lot books, but not as much experience yet.

liletian wrote on May 4^th, 2009, 9:05am:
There are many spectrum analyzer in Agilent.
http://www.home.agilent.com/agilent/product.jspx?nid=-536902453.0.00&cc=US&lc=en...
But I think your spectrum analyzer have built-in VSA89600 Vector Signal Analysis ability. Is it right ?
yes, I did not use this feather yet.:)

liletian wrote on May 4^th, 2009, 9:05am:
Use VSA89600 Vector Signal Analysis.
 Thanks, I will read manual and try to do it.
liletian wrote on May 4^th, 2009, 9:05am:
You can distinguish AM-Noise and PM(FM)-Noise.

liletian wrote on May 4^th, 2009, 9:05am:
I don't mean what probe you use.

It seems 50ohm is loaded directly in your observation point of circuit.
Your observation point of circuit have enough ability to drive load of 50ohm ?
yes, definitely!
Does it require high-impedance probing, such as Giga-Pico-Probe ?
no, for oscillator point, we did not need it!

pancho_hideboo wrote on May 6^th, 2009, 8:55am:

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