Noise from a Class C Amplifier - RF Cafe Forums

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Michael

Post subject: Noise from a Class C Amplifier Posted: Fri Jan 27, 2006 10:37 am

Good day.

This might be a simple question, but I need some assistance. I am looking at the noise generated by a Class C amplifier (to keep things simple, lets assume it is has a 10 watt amplifier) and how to measure it.

Also I would like to know if anyone has some suggestions about how to analyze the noise (instead of measuring it, can I perform some calculations and get an approximate answer?)

Finally, has anyone tried to simulate the noise from a Class C amplifier?

Any information will be appreciated - websites, magazine articles, books, etc.

Thank you

Michael

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IR

Post subject: Posted: Sun Jan 29, 2006 11:54 am

Joined: Mon Jun 27, 2005 2:02 pm

Posts: 373

Location: Germany

Hello Michael,

You can measure the output noise of the PA by using Spectrum Analyzer. You first have to measure the output noise when the PA is off, this result will be used as reference point, you have to know the temperature at which it was measured. Then turn on the PA and notice that the noise floor is increased. Make these measurements at the same RBW.

The difference between the noise floors at both cases is the gain of the noise + PA´s Noise Figure. Of course that the noise is also dependent on the BW of operation (RBW of the SA in this case) and the temperature according to: Pn=kTB

After this calculation, you can deduce the self-contribution of the PA to the noise measured.

Good luck!

_________________

Best regards,

- IR

Posted  11/12/2012