hi, can u elaborate on your question?

@Devashree panchayat

If we are designing a filter , we can use different methods ,using fss, metamaterial, etc

Then how we can say that this filter is particularly designed using fss

You can use the simulation results to demonstrate that your structure is functioning as a frequency-selective surface (FSS). An FSS is a type of surface that is designed to reflect or transmit specific frequency bands while suppressing other frequencies. To prove that your structure is an FSS, you can perform a full-wave simulation of the structure and compare the simulated reflection and transmission characteristics to your design specifications.