| Summary: | A broadband spaceborne reflectarray with high polarization purity is proposed for Ultra High Definition TV (UHDTV) broadcasting for direct-to-home (DTH) applications. The provided bandwidth would allow to offer DTH and other services, while the enhanced cross-polarization performance enables the improvement of a better signal-to-interference-plus-noise ratio. The broadband design procedure is based on a multi-resonant unit cell with several degrees of freedom (DoF) and an improved multi-frequency optimization algorithm. It is divided into several stages and sub-stages in order to facilitate convergence towards a broadband, contoured-beam, high-performance design, including the cross-polarization figure-of-merit in the procedure. A one-meter contoured-beam reflectarray working in a 20% frequency band with high polarization purity is presented as an example. The antenna is designed to fulfil the requirements of a European coverage for DTH UHDTV broadcasting in dual-linear polarization. The cross-polarization figure-of-merit greatly improves after the optimization procedure in the whole band, achieving values better than 37 dB in the coverage region, providing an excellent isolation between polarizations. This procedure can also be extended to other satellite applications in dual-circular polarization.
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