Overlapped and sequential metasurface modulations for Bi-Chromatic beams generation

This paper describes the generation of directive beams at two different frequencies with the same circular metasurface (MTS) antenna based on a surface wave (SW) excitation. Two methods are presented to achieve the desired bi-chromatic beam operation. The first one consists in mathematically superimposing two MTS modulations, each one matched to the SW wavelength at a different frequency. In the second method, the period of the MTS modulation matches the SW wavelengths at two different frequencies in two different regions of the antenna, i.e., close to the center for the high frequency band and close to the periphery for the low frequency band. The first method allows one to have different feed points for each beam in a self-diplexed structure, although it is also possible to use a single feed configuration and a diplexer. The second approach only holds for a single physical feed-point. Numerical and experimental results are shown.