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A class of radar systems known as passive radar, also known as parasitic radar, passive coherent location, passive surveillance, and passive covert radar, detects and tracks objects by processing reflected light from non-cooperative environmental sources, such as commercial broadcast and communications signals.
It is a specific instance of passive bistatic radar (PBR), a broad category that makes use of both cooperative and non-cooperative radar transmitters.
An exclusive transmitter is absent from a passive radar system. Instead, the receiver makes use of external transmitters and compares the times of arrival of the signal coming directly from the transmitter with the signal coming from the object’s reflection.
This makes it possible to calculate the object’s bistatic range. A passive radar would normally measure the bistatic Doppler shift of the echo as well as its direction of arrival in addition to the bistatic range.
These make it possible to determine the object’s position, heading, and speed. The accuracy of the final track can be greatly increased by using numerous transmitters and/or receivers to produce multiple independent measurements of bistatic range, Doppler, and heading.
Very small target returns must be picked up by a passive radar system in the presence of extremely potent, constant interference. In contrast, a traditional radar searches for echoes during the pauses in transmission between each pulse.
The receiver must therefore have a low noise figure, a large dynamic range, and a good linearity. Despite this, the system often operates with external noise limitations.
and the received echoes are typically well below the noise level (due to reception of the transmitted signal itself, plus reception of other distant in-band transmitters). Digital receiver systems are used by passive radar systems, and they produce a digitised, sampled signal.
The Global Passive radar market accounted for $XX Billion in 2022 and is anticipated to reach $XX Billion by 2030, registering a CAGR of XX% from 2023 to 2030.
A soldier-portable, covert radar system for air defence, land, and maritime surveillance, the MAVERICK M-series, will soon be available in a new iteration, according to Silentium Defence. It made available video of a drone flight that was used to monitor a remote property (pictured)
According to the business, the Maverick-S is a first in the capability that can simultaneously detect and track a wide variety of target types from the ground to low earth orbit.
The radar has been made smaller and has a wider range of applications thanks to the new technologies. Due to their increased efficiency, accuracy, and dual-use, 3D radar systems are attracting the attention of numerous businesses and military organisations throughout the world.
By measuring an object’s three spatial coordinates, the 3D radar technology can locate the target with extreme precision. In the defence and meteorological industries, 3D radars are currently displacing 2D radars more and more.
Another development has been the rise of passive radars, which are now the weapon of choice for militaries all over the world due to their affordability and effectiveness.
Through reflections from non-cooperative sources of illumination, such as traffic and communication signals, passive radar systems find and follow their targets. Simple antenna arrays with several antenna elements and element-level digitisation are used by the majority of passive radar systems.
This makes it possible to use conventional radar beamforming methods, such as amplitude monopulse utilising a succession of fixed, overlapping beams or more complex adaptive beamforming, to determine the direction of arrival of echoes.
As an alternative, several research systems have determined the direction of the echoes’ arrival using simply a pair of antenna elements and the phase-difference of arrival (known as phase interferometry and similar in concept to Very Long Baseline Interferometry used in astronomy).
Due to the strong and consistent direct signal received from the transmitter, the signal-to-interference ratio is the main factor limiting the detection range of the majority of passive radar systems.
In a method akin to active noise management, an adaptive filter can be employed to eliminate the direct signal. This phase is necessary to make sure that the direct signal’s range and Doppler sidelobes do not obscure the smaller echoes during the succeeding cross-correlation stage.
Cross-correlation is the most important processing step in a passive radar. In addition to serving as the matching filter, this step also calculates the bistatic range and bistatic Doppler shift of each target echo. Since most analogue and digital broadcast signals have a noise-like quality, they frequently merely correlate with one another.
