Effect of power supply ripples on RF PA/LNA

[Simo.Da]

Hello all,

I was using a bench power supply with 1mV of ripples to power up some RF power amplifiers/ LNAs.
If I used a different power supply with nearly 100mV of ripples, will that affect the PA/LNA performance? How to know at what level the PA/LNA's response will be affected? Does the phase noise test give any indication?

Any advices please?

 

[G4BCH]

Does the signal source analyser display discrete spurious signals, if so turn that function on, it will show the if the swither frequency is getting through. I have only used the Agilent E5052 and that had to have the display set to show spurs, it makes a big difference to the display if there are any single line spurs present.
Also check the input signal before it is amplified together with the suggestions made by biff44 as a comparison.

 

[Simo.Da]

First, oscilloscopes are NOTORIOUS for adding their own noise on top of what is actually there. your power supply might be much better than you think it is.

one thing you could do is make a phase noise and AM noise test with the power supply--use multiple measurement averages. then replace the power supply with a battery and a bunch of capacitors, and retake the phase noise test. Compare the two. then you know the effect of the additive noise of the amplifier. you might need to float the 3rd pin earth ground on your ac wall outlet on the power supply

also, it really depends on what MODULATION you are using (if a communications system), or what sort of subclutter visibility you need (if its a radar system). i do not see you mentioning the system application.

a 4FSK sytem is a cake walk compared to a 4096 QAM system!

Sorry, I didn't get how to float the earth pin!
I have tried to connect the earth of the power supply and the scope, and that has reduced the noise a little bit
I am not using any type of modulation. It is only a bunch of amplifiers and an IQ mixer for up and down conversion.
Will using a LISN be any good? I have attached a picture of the frequency content connecting to a linear power supply. The blue trace while there was no current draw, the black trace is after turning the DC electronic load.