  In this paper, a low radar cross section (RCS) patch antenna based on the
3-bit metasurface composed of linear polarization conversion elements is
designed. At first, 3-bit coding metamaterials are constructed by a sequence of
eight coded unit cells, which have a similar cross-polarized reflected
amplitude response and gradient reflected phase responses covering 0~2{\pi},
respectively. Equivalent circuit models (ECMs) of these unit cells are created
to describe their electrical behavior for the two linear incident polarizations
at the same time. Then, a patch antenna is integrated on the 3-bit metasurface,
of which the elements are placed with a 2-dimensional linear coding sequence.
The metal square ring is set around the patch antenna to protect it from the
disturbance of metasurface. Both the simulation and experiment results
demonstrate that the designed metasurface can primarily reduce the antenna RCS
at a broadband, while the antenna performances are not degraded significantly.
