Nice question. Its actually not easy to match the antenna performance to a circuit model across a large band. But basically you can start with a RLC circuit to model the band close to the resonance, and add other elements as needed.

In case youre using a toll like CST Microwave Studio, just import the measured S parameters (S1p file) from the VNA into Design Studio canvas. The you create the lumped circuit model too, and get the software optimize the RLC values as to make both S parameters the same (minimizing the difference S11-S22). 

The same can be done with ADS, Microwave Office and even Matlab.

Nice question. Its actually not easy to match the antenna performance to a circuit model across a large band. But basically you can start with a RLC circuit to model the band close to the resonance, and add other elements as needed.

In case youre using a toll like CST Microwave Studio, just import the measured S parameters (S1p file) from the VNA into Design Studio canvas. The you create the lumped circuit model too, and get the software optimize the RLC values as to make both S parameters the same (minimizing the difference S11-S22). 

The same can be done with ADS, Microwave Office and even Matlab.

Mostly, the RLC approach will work for narrow band antennas. But, for UWB antennas I think it is not possible.......

You need to see the book Hong J.-S. and Lancaster M. J. ‘Microstrip filters for RF/microwave applications’ John Wiley and Sons Inc. 2001 ISBN 0-471-38877-7

R-L-C connected in Parallel creates equivalent circuit where R represented loss factor and L store and forward magnetic field, C store and forward electric field 

hi Marcelo B. Perotoni, am using cst microwave studio software. can u please explain how to export the s parameters from VNA to  design studio canvas

Hi Aju

You get the .S1P or .S2P parameters, exported from your VNA. The on Design Studio you ask for the item "Touchstone file block", which is under the class "Data Import". There you will point the path to your .s1p/.s2p file, which will show up as a box with one or two ports, depending on your measurement. It can then be connected to other circuit elements on your canvas.

any one pls give brief clarification about to draw RLC circuit model for return loss by using MATLAB

you can draw the S11 on the smith chart from result in project tree and the you can determine the imaginary and real part part then you can predict the circuit

Project Manger Window

Result>>>Create Terminal Solution Data Report>>>> Smith chart

Hello Prof Marcelo B. Perotoni ,

have you worked on band pass filter ?? i am finding difficulty in drawing mode chart graph and also finding coupling matrix ofcoupled resonator filter using ADS..Do you have idea of finding them..Please help if know

Thanks

Nitin

Hi Nitin

I dont know ADS, my advice would go for Matlab instead.

Hi Nitin

I am not familiar with ADS, sorry...

Email me for further questions

Hi Yehya

I tried to send you a mail but is not going please i need more explanation regarding your paper on how to draw equivalent circuit of an antenna. [email protected] is my email address

Hello Adamu!

this is my email address: [email protected]

Please go through this link: https://www.radioeng.cz/fulltexts/2018/18_03_0646_0653.pdf.

Anveshkumar i checked the link that you have send but still i didnt understand how the equivalent circuit was extracted

This is a heuristic approach need lot of efforts and concept

In HFSS it is not possible to draw equivalent circuit of any antenna... Theoretically, you need to approximate the antenna in terms of R, C and L......

The input impedance of an antenna can be obtained from S11 since

S11= ( ZL-ZO)/ (ZL+ZO),

given S11 magnitude and phase and given Zo one can calculate ZL. By changing the frequency one can get ZL as a function of frequency and fins an equivalent circuit which is normally a parallel LC circuit shunted by the far field radiation resistance.

Best wishes

Please read the book

Antennas

by

Kraus

from

Ohio state university

Please look at the book by

Kraus

from

Ohio state university

USA