![]() An analytic approach is possible because all RTE are made of a few basic elements that have been analyzed and described thoroughly in the technical literature. My solution was to develop analytic models of all common RTE, calculate RCS over the entire range of aspect, and present the results in a color-coded analytic RCS diagram. Such a diagram is easier to interpret than multiple individual polar plots, but obtaining enough anechoic chamber data to produce a detailed diagram is costly and time consuming. The data visualization problem may be overcome by a single quantized, color-coded RCS diagram showing the data from many polar plots. Manufacturers sometimes provide several polar diagrams for different tilt angles, but this is not common practice and, even when the data are available, it is not easy to visualize performance given multiple polar diagrams. Consequently, single polar diagrams do not provide enough information to compare radar reflectors that are to be used on sailboats. It does not represent performance if the RTE is tilted away from the vertical, as would be the case if the RTE is mounted on a vessel that is rolling or pitching in a seaway or simply sailing at a constant angle of heel. A carefully calibrated radar system records the strength of the reflected signal as the platform rotates through 360° and graphs RCS against azimuth.Ī polar diagram describes the RTE as long as it is vertical (elevation is zero). To obtain polar diagram data, the target is mounted on a rotating platform in an indoor radar range (radar anechoic chamber). Radar cross section is commonly presented in a polar diagram. A complete characterization of a radar reflector includes the RCS at all bearing angles, or azimuths from 0° to 360° and all elevations angles from -90° to +90° – although a smaller range of elevation usually is adequate. For a radar dead abeam, the elevation angle is your vessel’s angle of heel for a radar dead ahead or astern, the elevation angle is your vessel’s pitch angle. The orientation, or aspect, is simply the relative bearing of the radar from your vessel and the elevation angle of the line of sight to the radar relative to your deck. Rather, the RCS depends on the orientation of the radar reflector relative to the radar that is painting it. Radar reflectors cannot be completely described by a single RCS value. Consistent detection is especially desirable for collision avoidance because your vessel may be missed by a human operator and it may be ignored by automatic radar plotting aid software. A larger RCS means the target will be detected at greater range, by lower power radar sets, in poorer weather conditions and more consistently. The strength of the radar signal reflected by a target is related to the radar cross section, or RCS. ![]() ![]() We’ll use it here to compare a few of the common passive radar reflectors on the market. How effective are these devices? For my recent book Radar Reflectors for Cruising Sailboats, I developed a method for describing and comparing RTEs. Because sailboats are notoriously poor radar targets, many sailors purchase a passive radar target enhancer (RTE), or radar reflector, to improve the vessel’s signature.
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