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However, in most fielded systems, unwanted clutter and interference sources mean that the noise level changes both spatially and temporally. In this case, a changing threshold can be used, where the threshold level is raised and lowered to maintain a constant probability of false alarm. This is known as constant false alarm rate (CFAR) detection.
In the mid-2000s, an improved version labeled YLC-2A was deployed to the PLA. Equipped with a new Giga-flops digital signal processor, it is capable of Digital Moving Target Indication (DMTI) and Constant false alarm rate (CFAR) processing. An S-band variation called YLC-2U with similar capabilities was also developed for SAM guidance.
It was discovered that the false alarm rate was high because the radar would pick up swarms of insects and clutter from mountainous terrain. The solution was to allow the operator to change the sensitivity profile of radar by periodically reducing attenuation, and setting threat and non-threat sectors according to changing environment.
A good PSR should have a designed false alarm rate of two or less false alarms per day. (A false alarm should not be confused with a nuisance alarm caused by, for example, an animal). Characteristics of some perimeter surveillance radar systems: Carrier frequencies range from C-band (about 5 GHz) to W band (about 77 GHz).
In addition, noise in the radar receiver will occasionally exceed the detection threshold of the radar's Constant false alarm rate detector and be incorrectly reported as targets (known as false alarms). The role of the radar tracker is to monitor consecutive updates from the radar system (which typically occur once every few seconds, as the ...
Most radar detectors feature a mute button so you can manually turn off false alarms. Some of the latest software is used to filter out frequent false signals by learning where they commonly occur.
The AN/AAR-47 passively detects missiles by their infrared signature, [3] and uses algorithms to differentiate between incoming missiles and false alarms. Newer versions also have laser warning sensors and are capable of detecting a wider range of threats. After processing the nature of the threat, the system gives the pilot an audio and visual ...
This can be adapted for systems that lack a coherent transmitter, such as time-domain pulse-amplitude radar. Constant false alarm rate, a form of automatic gain control (AGC), is a method that relies on clutter returns far outnumbering echoes from targets of interest. The receiver's gain is automatically adjusted to maintain a constant level of ...