  This paper proposes a flexible broadband linear polarization converter based
on metasurface operating at microwave band. In order to achieve bandwidth
extension property, long and short metallic arc wires, as well as the metallic
disks placed over a ground plane, are combined into the polarizer, which can
generate three neighboring resonances. Due to the combination of the first two
resonances and optimized size and thickness of the unit cell, the polarization
converter can have a weak incident angle dependence. Both simulated and
measured results confirm that the average polarization conversion ratio is over
85% from 11.3 to 20.2 GHz within a broad incident angle from 0{\deg} to
45{\deg}. Moreover, the proposed polarization converter based on flexible
substrates can be applied for conformal design. The simulation and experiment
results demonstrate that our designed polarizer still keeps high polarization
conversion efficiency even when it adheres on convex cylindrical surfaces. The
periodic metallic structure of the designed polarizer has great potential
application values in the microwave, terahertz and optic regimes.
