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LC VCO poor phase noise @1MHz

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R

rty94

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Hello,

I am designing a 5GHz LC tank VCO and it shows -89dbC/HZ @1Mhz phase noise..Which are the best techniques for making it acceptable?
 

First, some investigation of whether this is truly random
noise, or has external components such as supply ripple,
ambient EMI and so on. Also check that the measurement
system is set up such that open socket noise floor is way
lower (spectrum analyzer span has large effect on this).

Although when you say "designing", present tense, maybe
this is a simulation type question (however things like FFT
window may have the same consequences re noise floor).
 

There is no such Best Design Method..Principal Phase Noise Contributions are;
-Quality Factor of the Tank Circuit
-Noise Factor of the Active Device
respectively.If you especially design a high Q Factor Tank Circuit, PN will obviously be improved.
There are some other " particular" techniques to improve Phase Noise but I have mentioned the Principal Contributors.
More info can be found Rohde's Textbook.
Also read his' App. Notes @ **broken link removed**
 

This is really bad, make sure this isn't caused by noise on the VCO tuning voltage.
 

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