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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.
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).
At the time, the railSAR fell into the highest category of UWB radar systems, operating across a 950 MHz-wide band from 40 MHz to 1 GHz on a pulse strength of 2.5 megawatts. [1] [3] [4] It provided fully polarimetric, high resolution radar data and possessed 185% bandwidth compared to other radar systems that had less than 25% bandwidth. [1] [5]
The AR-320 is a 3D early warning radar developed by the UK's Plessey in partnership with US-based ITT-Gilfillan.The system combined the receiver electronics, computer systems and displays of the earlier Plessey AR-3D with a Gilfillan-developed transmitter and planar array antenna from their S320 series.
During use, it was discovered that the false-alarm rate was high due to the radar detecting swarms of insects and clutter from nearby mountainous terrain. [4] Although problematic for a military air defence radar, this is ideal for a weather radar , and made phased array radars a prime candidate for implementation in the meteorological spectrum.
The Hughes AN/ASG-18 Fire Control System was a prototype airborne radar/combination system for the planned North American XF-108 Rapier interceptor aircraft for the United States Air Force, and later for the Lockheed YF-12. The US's first pulse-Doppler radar, [4] the system had look-down/shoot-down capability and could track one target at a time.
The false positive rate is calculated as the ratio between the number of negative events wrongly categorized as positive (false positives) and the total number of actual negative events (regardless of classification). The false positive rate (or "false alarm rate") usually refers to the expectancy of the false positive ratio.
7.2.4.2 Underground construction. ... imaging systems, lasers, or laser radar ... both surface and buried minefields is achieved with very low false alarm rates.