Can a separated receiver defeat the world's most advanced stealth aircraft?
In short: Traditional radar relies on a single unit to both send and receive signals. But by splitting the transmitter and receiver apart, a bistatic radar system creates a geometric trap that stealth coatings and specialized shapes may struggle to evade.
In a conventional monostatic radar, the transmitter and receiver are co-located. This makes the system vulnerable to stealth technology designed to deflect signals away from the source. Bistatic radar changes the geometry by separating the transmitter and receiver by a distance comparable to the expected target distance. This separation creates a 'bistatic angle' between the three points. When this angle is near 180 degrees, the system functions as a forward scatter radar, detecting targets passing between the two stations.
Forward scatter radar is particularly potent against stealth aircraft. Under such settings, the aircraft's silhouette from the transmitter's perspective dictates the radar cross section (RCS), rendering stealthy airframe shaping or coatings mostly irrelevant. The RCS in this mode can be modeled using Babinet's principle, where the scattering depends on the silhouette area and the radar wavelength. However, this method faces significant hurdles: tracking is difficult because the information content for range, bearing, and Doppler shift tends toward zero as the target moves through the 'fence'.
Beyond combat, these systems offer unique advantages. Passive coherent location (PCL) systems, or passive covert radars, do not emit their own pulses. Instead, they exploit 'transmitters of opportunity,' such as commercial signals, to detect targets. This can lower procurement costs and increase resilience to electronic countermeasures, as an adversary may not know the receiver's location or the waveform being used. However, these benefits come with trade-offs, including the high cost of communication between separated sites and a reduced ability to provide low-level coverage due to the necessity of line-of-sight.
The physics of bistatic radar also enables advanced imaging. By analyzing how signals reflect, researchers can use bistatic imaging to differentiate between materials, such as distinguishing ice from rock on the lunar surface by detecting volume scattering versus surface scattering.
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- Summary by Intellect · source: Bistatic radar
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