I understand you don't need a manual, but with the help of Foster canonical form, the equivalent circuit of a single band or multiband antenna can easily found.

Anil Pandey : ‘Antenna Design for Wireless Communication and Mobile Phones’, in ‘Practical Microstrip and Printed Antenna Design’ (2019), pp. 58–59

You can extract the impedance of an antenna vs frequency from any Full-wave software and then synthesize the impedance with many circuits, but there are some constraints which will be applied in circuit synthesis process to get desired circuit.

Have a look on this interactions please:

https://www.researchgate.net/post/How_can_we_determine_equivalent_circuit_model_of_an_antenna_using_CST_and_ADS

https://www.researchgate.net/post/How_to_view_Equivalent_Circuit_Model_export_from_HFSS

https://www.researchgate.net/post/How_to_draw_equivalent_circuit_model_for_antennas

https://www.researchgate.net/post/Is_there_any_procedure_to_extract_the_equivalent_lumped_circuit_model_of_a_patch_antenna_designed_using_HFSS

https://www.researchgate.net/post/How_can_we_get_equivalent_circuit_of_our_radiating_patch_in_HFSS

This papers may also help you:

Typical Approach of Modeling Lumped Equivalents for Narrowband Antennas

Lumped equivalent models of narrowband antennas and isolation enhancement in a three antennas system.

It seems like the most elegant is the method developed by Prof Brazil. This method employs direct conversion of a measured/simulated antenna S matrix, even multi-port, into an equivalent circuit made of transmission line delays and a few more basic circuit components. The conversion algorithm is physically explicit, numerically robust, and simple to implement in few lines of computer code, say in Matlab or Python. See more in the attached.

Refer to the following textbook which is considered as one of the most popular and classical books on antennas:

Balanis, Constantine A. Antenna theory: analysis and design. John wiley & sons, 2015.

Just keep in mind that EVERY antenna is basically a transformer between the incoming signal (via coax or waveguide feed).. in case of a transmitting antenna..(receiving antenna all the same same just reciprocity) and the radiation (far) field which can (but not must be) be represented as a superposition of homogenous (and in some cases also inhomogeneous=evanescent)plane waves. Caveat about the near field which can store a considerable amount of reactive power. Also caution about a sort of of superluminal claims in the nearfield of antennae..in this case ususally the Jackson caveat is forgotten.

only ADS software can give you the electrical equivalent of a designed antenna. you can export file , open in ads, generate its layout and electrical equivalent ckt.

Balanis, Constantine A. Antenna theory: analysis and design. John wiley & sons, 2015.

&

Anil Pandey : ‘Antenna Design for Wireless Communication and Mobile Phones’, in ‘Practical Microstrip and Printed Antenna Design’ (2019).

You can use Advanced Design System (ADS) by exporting the file from CST.

You could use ADS adgilent!

See my paper brother

https://ieeexplore.ieee.org/abstract/document/9625942/

Hello dear,

you can see my paper, I have already proposed an equivalent circuit model of an antenna and have already declared that each element represents.

http://dx.doi.org/10.1155/2021/9973839

Dear sir,

You can investigate the values of the lumped elements by importing the S11-parameter of the antenna to ADS and then tuning the lumped elements to get the same behaviors.

Each part of the antenna structure can be analyzed in CST, and equivalent lumped elements can be found/investigated using S-parameters and Smith Chart. Then use the ADS or MWO to optimize and find the equivalent circuit of the overall radiating antenna.

You can use ADS to optimize the parameters and get a similar result as your measured or simulated