The SR-71 Blackbird and other aircraft were painted with a special " iron ball paint" that consisted of small metallic-coated balls. Chaff is often made from metallised plastic or glass (in a similar manner to metallised foils on food stuffs) with microscopically thin layers of metal.Īlso, some devices are designed to be Radar active, such as radar antennas and this will increase RCS. Even a very thin layer of metal can make an object strongly radar reflective. Wood and cloth (such as portions of airplanes and balloons used to be commonly made) or plastic and fibreglass are less reflective or indeed transparent to radar making them suitable for radomes. Materials such as metal are strongly radar reflective and tend to produce strong signals. For example, 10 cm (S-band radar) can detect rain drops but not clouds whose droplets are too small. Also, radar of one band may not even detect certain size objects. A target's RCS depends on its size, reflectivity of its surface, and the directivity of the radar reflection caused by the target's geometric shape.Īs a rule, the larger an object, the stronger its radar reflection and thus the greater its RCS. In general, RCS is a strong function of the orientation of the radar and target, or, for the bistatic (radar transmitter and receiver not co-located), a function of the transmitter-target and receiver-target orientations.
Thus, RCS allows the performance of a radar system with a given target to be analysed independent of the radar and engagement parameters. However, RCS is an extremely valuable concept because it is a property of the target alone and may be measured or calculated. In those situations, it is useful to use a related quantity called the differential scattering coefficient (also called the normalized radar cross-section or backscatter coefficient) σ 0 ("sigma nought"), which is the average radar cross-section of a set of objects per unit area: In some cases, it is of interest to look at an area on the ground that includes many objects. RCS data for current military aircraft is mostly highly classified. RCS is integral to the development of radar stealth technology, particularly in applications involving aircraft and ballistic missiles. For example, a stealth aircraft (which is designed to have low detectability) will have design features that give it a low RCS (such as absorbent paint, flat surfaces, surfaces specifically angled to reflect the signal somewhere other than towards the source), as opposed to a passenger airliner that will have a high RCS (bare metal, rounded surfaces effectively guaranteed to reflect some signal back to the source, many protrusions like the engines, antennas, etc.). Radar cross-section is used to detect airplanes in a wide variation of ranges. While important in detecting targets, strength of emitter and distance are not factors that affect the calculation of an RCS because RCS is a property of the target's reflectivity. the polarization of the transmitted and the received radiation with respect to the orientation of the target.
the reflected angle (angle at which the reflected beam leaves the part of the target hit it depends upon incident angle).the incident angle (angle at which the radar beam hits a particular portion of the target, which depends upon the shape of the target and its orientation to the radar source).the size of the target relative to the wavelength of the illuminating radar signal.
0 kommentar(er)
