I have designed a bilayered structure on CST which is having copper patches as upper and bottom layers and a substrate sandwiched in between but I want LC equivalent circuit for the whole structure.
Dear Asfandiyar Khan thanks for asking this very interesting technical question on RG. As an inorganic chemist I'm absolutely not a proven expert in this field. However, I know that it often pays off to search the "Questions" and "Publications" sections of RG directly for helpful hints. In this context please have a look at the following closely related technical questions which have been posted earlier on RG. It might help you in your analysis when you check the answers given to those questions:
How can extract antenna equivalent circuit from CST microwave studio?
In Microstrip Patch antenna you can easily calculate the inductance, resistance and capacitance based on the Length, Width, Height and type of the material used in the design of the microstrip lines.
You can refer the following book for conversion of microstrip lines to equivalent circuit
Passive RF and Microwave Integrated Circuits by Leo G. Maloratsky