# Nonlinear model of amplifier simulation using SDD

1. ## [Moved]: How to simulate DC Nonlinear model?

Hi,

I have an equation that describes the linearity of my amplifier. and I want to make a plot based on the equation. How could I do that in ADS?

this the equation I have vo=a1+a2vi+a3vi^2, and I want to plot vo vs vi...

Please help,

thanks

•

2. ## Re: How to simulate DC Nonlinear model?

Can you create a lissajous figure? It's the natural choice.
Excellent for observing whether your amplifier introduces distortion.

3. ## Re: How to simulate DC Nonlinear model?

Originally Posted by Freestylesoap
I have an equation that describes the linearity of my amplifier.
and I want to make a plot based on the equation.
How could I do that in ADS?
this the equation I have vo=a1+a2vi+a3vi^2, and I want to plot vo vs vi...
It is very easy.
Use SDD(Symbolically Define Device) or Verilog-A.

http://edadocs.software.keysight.com...efined+Devices
http://edadocs.software.keysight.com...he+SDD+and+UCM

4. ## Re: How to simulate DC Nonlinear model?

Originally Posted by pancho_hideboo
Hopefully it's not too late to get back to you. Thank you for your help. The SDD example is really helpful.
I tried out the example, but it doesn't work as what I expect. Compression point, OIP2, and OIP3 do not match to my original amplifier.

I have the equations set up as follows.. K1, K2, and K3 are calculated base on gain, OIP2, and OIP3. Do I input anything wrong here?

•

5. ## Nonlinear model of amplifier simulation using SDD

Hi all,

I would like to come up with a DC nonlinear model of an amplifier. I calculated k1, k2, and k3 based on gain, OIP2, and OIP3 of the amp. And now, I need to simulate the output voltage equation vo=k1vi+k2vi^2+k3vi^3. I use SDD2P block to simulate(as shown in the pictures below), but I could not get similar OIP2 and OIP3 values by doing HB simulations. Does anyone know what I've done wrong in the simulation setup?

Thank you so much!

•

6. ## Re: Nonlinear model of amplifier simulation using SDD

Originally Posted by Freestylesoap
I calculated k1, k2, and k3 based on gain, OIP2, and OIP3 of the amp.
Show me equations for k1, k2 and k3 you use.
http://edadocs.software.keysight.com...pageId=5923594

And you use "vi" in SDD without defining it.

7. ## Re: How to simulate DC Nonlinear model?

Originally Posted by Freestylesoap
Hopefully it's not too late to get back to you.
You were online on 19th March 2017 at least.
Respond quickly.

8. ## Re: Nonlinear model of amplifier simulation using SDD

Originally Posted by pancho_hideboo
Show me equations for k1, k2 and k3 you use.
http://edadocs.software.keysight.com...pageId=5923594

And you use "vi" in SDD without defining it.
The main page keeps saying there's no new reply for me. That's why I didn't open the page. Sorry!
I use vi=_v1. I set up the variables as shown in picture. Really appreciate your help!!

9. ## Re: Nonlinear model of amplifier simulation using SDD

No.
I request equations for k1, k2 and k3.

•

10. ## Re: Nonlinear model of amplifier simulation using SDD

Originally Posted by pancho_hideboo
No.
I request equations for k1, k2 and k3.
vi=Acos(w1t)+Bcos(w1t); vo=k1vi+k2vi^2+k3vi^3
Gain=20log(K1) -> get K1
OIP2=2Po-IM2, IM2=10log((A^2*K2)/(2*z0))[dBm] -> know OIP2 and Po, so get K2
2OIP3=3Po-IM3, IM3=10log((A^3*K3*3/4)/(2*z0))[dBm] ->know OIP3 and Po, so get K3
Hope it makes sense.

11. ## Re: Nonlinear model of amplifier simulation using SDD

First, set k2=0.
Can you get reasonable results when k2=0 ?

I think your equations for k2 and k3 are very suspicious.
See http://www.designers-guide.org/Model...rf-systems.pdf

There are many definition of IM2.
And IM2 is out of band.
Show me definition of your IM2.

--[[ ]]--