pancho_hideboo wrote on May 4th, 2009, 9:11am:It seems you don't have much experiences of actual measurements.
liletian wrote on May 4th, 2009, 9:05am:Can you explain more free running state?
It is "not locked state".
so for unlocked state, the spectrum is very dirty?
liletian wrote on May 4th, 2009, 9:05am:In which state it will be better spectrum?
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 4th, 2009, 9:05am:I use agilent spectrum analysizer to measure it
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 4th, 2009, 9:05am:how yo measure envelope_amplitude v.s. time ? Frequency Deviation v.s. time ?
Use VSA89600 Vector Signal Analysis.
Thanks, I will read manual and try to do it.
liletian wrote on May 4th, 2009, 9:05am:what's the use of it?
You can distinguish AM-Noise and PM(FM)-Noise.
liletian wrote on May 4th, 2009, 9:05am:and GSG probe.
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!