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![]() With actual radomes, framework shadowing is more complicated and depends on the radome geometry. The framework blockage length depends on the antenna scan angle and may vary from 0 up to the antenna diameter length when the framework member just bisects the reflector diameter. As the radome protected antenna scans in azimuth, the framework shadows the antenna aperture starting from one edge, continuing over the antenna and then passing out the other side. If we cut the radome vertically in half, we now have 2 panels and one framework seam member. Radome Geometry and Framework ShadowingĬonsider a perfect radome (truncated sphere) without any panels. ![]() Nevertheless, the antenna pattern is still degraded by scattering from the feed support struts, but mostly in the not measured 45-degree pattern directions. Then when azimuth and elevation antennas patterns are measured, these measurement pattern cuts do not show the effects of feed support strut scattering. Antenna engineers have long since learned to orient feed support struts at 45-degree angles relative to the principle horizontal, vertical planes. In contrast, where the antenna pattern is strong, the first several sidelobes are affected by only 1 dB. Here the antenna sidelobes may be affected from framework scattering by 6 to 12 dB. For the most part, the scattered energy is directed into the far out sidelobes where the antenna sidelobe pattern is very weak. The precise details of where this energy goes is dependent on the shadow length and radome transmission loss, the electronic signature of the framework and the positions and orientations of the framework members shadowing the reflector. Since sidelobes have small energy, the larger the radome scattering loss, the larger the effect on antenna sidelobes. ![]() The antenna pattern is corrupted by the scattering loss. What happens to this scattered energy is that it spreads out into the antenna sidelobes. For example, if the framework shadowing length is twice another radome, so is the radome scattering loss (transmission loss). In general, a larger scattering loss is encountered for a longer length framework shadowing the antenna aperture. Therefore, one must take into account the radome panel framework scattering loss in order to understand radome performance for protected antennas or radar. While radome wall insertion loss is typically less than 0.1 dB, surprisingly, the scattering loss off the framework is 4 to 100 times larger than the wall insertion loss. From an antenna point of view, just as the antenna feed assembly, feed support struts or cassegrain subreflector block the antenna aperture, in the same fashion so does the radome framework that shadows the antenna aperture. Radome transmission loss is the sum of the ordinary insertion loss of the antenna (radar) signal passing through the radome wall plus the scattering loss off the radome panel framework blocking (shadowing) the antenna aperture. Both the radome shell wall and panel framework are in the path of the shielded antenna. After assembly, the panel flange perimeter members form a framework characteristic of the panel shapes. Each radome panel is surrounded by a flange perimeter enabling adjacent panel assembly. Radome Design Considerations for Satellite Earth Stations Introduction Radomes are composed of panels, which when assembled form a truncated spherical shell to protect the enclosed antenna from the environment.Compliance of Satellite Earth Station Antenna Patterns.Stealth Radome Technology for Dual Pol Polarimetric Radar.Radome Noise Temperature and Antenna System dG/T Degradation.Transmission Loss and Framework Electronic Signature.Radome Geometry and Framework Shadowing.Radome Transmission Loss and Antenna Pattern Degradation Radome Transmission Loss
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