LC circuit in ADS-any comment will be appreciated....................................

Hi all,

I was trying to simulate a LC circuit in ADS: 1nH series with 1pF in parallel, so 3-dB cut of frequency gives by calculation is 5GH but my simulation result shows 6GHz--I am attaching the document here, pls do comment if you have any.

Thanks

Your formulae is valid for open circuted low pass filters only.If you do the math, you'll obtain the same result

Hello BigBoss,

what formula are you pointing to?

In ADS its a double terminated LC filter I have used, but it doesn't correlate with the equation I have used! I would like to have the correlation between theorytical calculation and simulated results-whats the best approach to it?

your comments will be appreciated

Simply you can not understand S21 correctly.

Calculate S21 correctly.
The Designer's Guide Community Forum - s-parameter calculation using ac analysis

S21=(2*V2/E)*sqrt(R01/R02)=(V2/(E/2))*sqrt(R01/R02), is it the equation I should be using for my calculation? If so how do you determine E & V2?

I am using the following eq
Voltage gain=(S21/2)((1-gamma_S)*(1+gamma_L)/(S11*gamma_S-1)*(S22*gamma_L-1)-S12*S21*gamma_S*gamma_L). I have Zs=Zl=50ohm , so gamma_S and gamma_L can be calculated. Simplyfied equation is
Voltage gain=S21*50, but I still do not get any correlation between simulation and simulated results.

Your comments will be appreciated BigBoss!

Surely learn concept of S-parameters.

Yes.

You can set any value as E. Since a factor which we have an interest on is a ratio of V2/E .
So you can set E=1.
If you set E=1, V2 can be determined uniquely since R01 and R02 are known.

Still you can not understand S21 at all.

Calculation of S21 from (2*V2/E)*sqrt(R01/R02) for your simple inverse L topology circuit is a task of kindergarden level.

But if you can not calculate S21 from (2*V2/E)*sqrt(R01/R02), calculate Y or Z parameters and then convert them to S-parameters.

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