In terms of which of its parameters? For example, radiation resistance, loss resistance, input impedance etc?

what kind of antenna? for example, there is a good analysys of patch antenna in balanis book.

We are assuming that you want to exact equivalent L,R,C parameter for a given antenna. Suppose, you got your result, then these parameters i.e. L, R and C can easily be utilized to represent radiation resistance, losses, input impedance, S11 etc because all are inter-related. Now the question is, how to exact these parameters.

Suppose, you want to model TM10 mode. Then, assume approximate L, R and C value and tune it using ADS or any other software. here, antenna parameters are fixed. For next mode, use similar procedure and exact different L, R and C values. In this way, researchers generally exact the equivalent L, R C value for different mode (or frequency)

If you do not have ADS, then use "network synthesis" procedure to exact L, R and C for a given mode (or frequency). We generally match our results with S11 for antenna case. M E Valkenburg, E A Gullemin, Tames & Lapatra etc may help you to learn circuit synthesis procedure.

Personally, I prefer to use second procedure instead of using ADS or any other software. If you use paper and pencil to exact L, R and C values, you will learn the subject. Software does not know any thing.

I have s parameter results and i want to map them to get equivalent circuit .My Antenna type is  meandered monopole type with some additions like gaps and matching network etc.Now how should i start whether on paper or ADS.If on paper how to account for the structure to map to equivalent components?? Is any antenna model can be started by RLC circuit??

I see . . .

It may be that the publications of Cartel, Haider, and Yarovoy (see http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6565790) as well as that by Sayidmarie and Yahya (http://article.sapub.org/pdf/10.5923.j.ijea.20140402.01.pdf) will be of help

Paper and pencil will take long time whereas you can easily find the equivalent RLC parameters using ADS. Although I prefer to work using first method, but for simplicity, you can use ADS. As you are investigating Monopole (meandered), it is better to follow R W P king/Schelkunoff's papers to learn transmission line model. From that you can get an idea how to deal monopole antenna. Solve at least one published problem by yourself. Verify all results with published data. then go for your work. Best book on transmission line mode: "Transmission Line Theory_Ronold W. P. King_1965"

thank you for reply and guidance .can you guide me steps to start with in ADS? I am new to it.

I never work on ADS.....These are the basic steps....If you have ADS, then use it to represent an Antenna using RLC ckt and tune it. Take example from Balanis's antenna book and verify results. No need for other example.

thanks sudipta so much...but as i am not working on patch antennas rather on meandered design so can you refer me any example related to meandered design??

I'm little bit confuse. You are working on meander. its is correct. Where will you apply it? Or, can you tell me your working area using meandering technique. I'm waiting for your reply....

Hi Sudipta...well mine is RFID tag antenna design at UHF band

Please try to contact Prof. Nemai karmakar, Monash University, Australia. Just give google search. You will get all information....

thank you much Sudipta....so nice of u.......I will try.....

Please go through this link:

https://www.radioeng.cz/fulltexts/2018/18_03_0646_0653.pdf.