Lumped Elements Modelling in ADS

Dear All,

Does anyone can show me a example of how to implement a customized lumped element in ADS which is independent of frequency ?

For example, I want to simulate an reactive element (jB) shunt to ground where the susceptance B is idependent of the frequency. So I imagine it requires to implement a box or work around in the equations, but I appreciate if someone of you can come with a example showing how to do it in ADS (Advanced Design System).

Thanks !

OK - if I understand it right, you want to make a (somewhat magical) simulation component which, having some susceptance, would normally alter its value with frequency, BUT - you want to mathematically mess with it such that it provides a constant reactive value, even as you alter the frequency... I think.

You would have to test out, or decide beforehand, the sign, to select the scaling equation. It all depends on whether you want a inductive susceptance, or a capacitive susceptance.

For a capacitive susceptance B(C) = 2*pi*f*C where f is frequency and C is capacitance.
You can see that it is proportional to frequency. Therefore, you scale by dividing by frequency to make it blind to that variable.
For example, your simulation C capacitance will appear to have a constant susceptance if you make it Csim=C/freq.

IF the component type has susceptance coming from inductance, then it is all the other way up.

For a inductive susceptance B(L) = 1/(2*pi*f*L) where L is the inductance.
To simulate this susceptance into staying constant, you need to replace L with a value L(sim) = L*freq.

This is just me thinking out loud. Try it. If I got it wrong, I am sure someone will tell us

OK, thanks but now how to implement it in ADS ? Anyone knows ?

With nearly every simulation software, instead of automatic sweep, you can set a variable. Either make the frequency be set by the variable, and sweep that parameter, or if you like, do it the other way around, and have the variable track the frequency.

You then have a variable to use to meddle with the other values. You may have to include the the suitable 10^n constant in with it if you are not using Hz and Farads, to keep the units correct.

BUT! .. I have gone along with this so far because I was curious about the motivation. The makers of simulation software have taken a lot of trouble to take the pain out of figuring how reactive components really behave. Reactive components do notice the frequency!

The wonderful point where the inductive susceptance equals the capacitive susceptance except for sign, and we get the tuned resonance.. is what we need to know! Why would you deliberately want to knobble that simulation by making a susceptance that does not behave the way it would in nature?

"Nature cannot be fooled" - Richard Feynman..

- - - Updated - - -

With nearly every simulation software, instead of automatic sweep, you can set a variable. Either make the frequency be set by the variable, and sweep that parameter, or if you like, do it the other way around, and have the variable track the frequency.

You then have a variable to use to meddle with the other values. You may have to include the the suitable 10^n constant in with it if you are not using Hz and Farads, to keep the units correct.

BUT! .. I have gone along with this so far because I was curious about the motivation. The makers of simulation software have taken a lot of trouble to take the pain out of figuring how reactive components really behave. Reactive components do notice the frequency!

The wonderful point where the inductive susceptance equals the capacitive susceptance except for sign, and we get the tuned resonance.. is what we need to know! Why would you deliberately want to knobble that simulation by making a susceptance that does not behave the way it would in nature?

"Nature cannot be fooled" - Richard Feynman..

Some have fair understanding on the view of nature behavior or even are limited to classical teachings.

Similarly, when Veselago hypothesized that a material with a negative refractive index could exist (metamaterials might not have even been discovered at that time), many scientists initially held onto their theoretical laws, arguing that a negative index of refraction was impossible they were reluctantly forced to rewrite all the textbooks on optics.

I could mention you a number of applications (such as a wide-band nearly constant susceptance waveguide element or a complex gyrator circuit or even in the theory and design of microwave filters, etc...) where the susceptance is nearly independent to the frequency (my application demands a behavioral model which is theoretically frequency independent in the simulation domain).

BTW, meanwhile I find out how to implement it in Agilent ADS, this was my motivation.

"The first principle is that you must not fool yourself, and you are the easiest person to fool" - Richard Feynman..

The quick and easy way to do it for any simulator is to simply make a 1 port model in a text file as below.

# MHZ S MA R 50
0.01 1 90
10000 1 90

This linear 1 port s parameter model gives a constant reactance of 50 ohms from 10kHz through to 10GHz (i.e. it has a constant 90deg phase angle for the reflection coefficient regardless of frequency)

Assuming your simulator interpolates between these two values then you will get this constant 50 ohm inductive reactance everywhere from 10kHz to 10GHz for the 1 port linear model :)

So save the text above as a *.s1p file and import it as a 1 port s parameter model?

To get a different constant reactance then simply change the angle from 90 to something else on lines 2 and 3...

In ADS you can use equation based models, under "Eqn Based-Linear":
Insert your 1,2... (or what ever you want) - port component as Z or Y and enter your susceptance!

Finished!

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