A design was presented for a multi-functional metasurface for in-band wavefront and polarization conversion,and out-of-band radar cross-section reduction to address the design problem of versatile microwave composite materials operating under complex electromagnetic environments.The identical transmission phase gradient and aptotic transmission phase difference of π/2 were maintained along the two orthogonal transverse directions of the layered metasurface to achieve the reciprocal conversion between circularly-polarized plane wave and linearly-polarized spherical wave.Meanwhile,a circuit analog absorbing structure was constructed through cascading a frequency-selective lossy layer,which effectively reduced the out-of-band radar cross-section of the layered metasurface.Further,a linearly-polarized tapered-slot element was used as the primary radiation source positioned at the phase center of the spherical wave.The secondary radiation with an augmented gain as well as circular polarization sense was observed within a wide band along the main lobe direction after transmission conversion by the metasurface.The bandwidth of gain augmentation is 57.14％,and the 3 dB axial ration bandwidth is 35.50％along the main lobe direction.The radar cross-section is reduced by more than 10 dB within a maximum bandwidth of 113.12％around the lower-band outside the transmission window.Relatively good angular stability was observed for this radar cross-section reduction effect.The agreement between measured and full-wave simulated results validates the presented design.
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