Microwave analog of optical theorem for transformation media application

We experimentally demonstrate optical theorem can be employed to obtain the scattering cross-section (SCS) for transformation media. Different from the total scattering-field integration approach, the optical theorem method is a transmission-like measurement for SCS characterization, and furthermore facilitates accessing the broadband spectrum for bandwidth evaluation. In order to examine this measurement method, we measure the SCS of a field concentrator, which is a transformation medium with multiple working frequencies [15], at microwave frequencies 2-18 GHz, and make comparison with the results from the field integration calculation. The experimental curves agree with the numerical ones. Our work presents an efficient implementation to observe the SCS for transformation devices with multi-band or broadband properties.