| 摘要 |
The reflector is for electromagnetic waves, and can turn one quarter of the polarisation direction in the reflected waves, and at the same time within two widely differing frequency bands, such as those with frequencies in the proportion of 4 to 1. For polarisation turning, two wire grids comprising parallel metal wires are placed parallel to a metal reflector's surface, and at different distances from it. Both wire grids are encased by a layer of dielectric material and the same material is between the reflector's surface and the grids. The distance from each of the grids to the surface of the metal reflector is in a ratio between 0.11 and 0.13, the distance being calculated in wavelength in the dielectric material. A cassegrain type aerial with a main reflector and one secondary is used for electromagnetic wave transmission and reception within the two very different frequency bands. (Provisional Basic advised week E36) |
