[HELP] How to measure S-Parameters of a PA?

[bagel520]

Hi!

I use RF-2192 as the power amplifier in my codeless phone design. I've got a problem now. The PA oscillates at some output impedance. So I think I should try to get the S-Parameters of PA and draw the stability circles. Then I can avoid the output impedance being at the unsable area on Smith Chart.

But another problem is how to get the S-Parameters of the PA? The information doesn't be included in the datasheet. And S-Parameters is changed by different bias condition and operating frequency.

The best way to get the right S-Parameters is to measure it directly. But how?

Thanks!

 

[pthoppay]

Hi,

First understand that S-parameters are for small signal analysis and hence cant beused for PA.

Since PA are large signals even if you have S-parameters, I dont think it will help. So better to think in other angles or contact the RF micro devices customer care to get more help, i have contacted them they really help a lot in solving probelms .

Prakash.

 

[boy]

There is a large signal network analyzer. It is avaliable from https://www.maurymw.com/

 

[BigBoss]

In generally small signal s-parameters are not very useful to design a PA. Because under the large signal conditions, these parameters are not valid anymore.Instead, to characterize a PA (or a large signal transistor) is to use either if it's possible slide tuner and find optimum load impedance or use a simulator if the nonlinear model of the component is available.

But first attempt is to use small signal s-parameters to validate impedance matching even tough under the large signal condition they won't be valid anymore.

And then the best method is to use automatic slide tuner but simple trombone will also able to work with some care.

Briefly, to design a PA is in fact to development by test and measurement.

Otherwise to obtain nonlinear models,characterize with large s-parameters is not very accurate and quite tedious.