Adaptive constant false alarm rate circuit with extremely low loss
AssigneeNorthrop Grumman Corporation
InventorPeter A. DeCesare
Life of this patent
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Abstract
A false alarm rate is maintained at or below a desired rate over a fluctuating mean noise level for providing additional sensitivity and increased range performance in a constant false alarm rate (CFAR) circuit in a radar system by: utilizing a variable CFAR detection threshold level for distances out to the radar's horizon; and, for distances beyond the radar's horizon, utilizing a relatively low fixed CFAR detection threshold level in place of the variable CFAR detection threshold level when there are no environmental factors present that produce additional radar returns.
Claims21
A method of maintaining a false rate at or below a desired false alarm rate over a fluctuating mean noise level so as to provide additional sensitivity and accordingly increased range performance in a constant false alarm rate (CFAR) circuit in radar system, comprising the steps of:
- utilizing a variable CFAR detection threshold level for distances out to a predetermined range;
- and
- for distances beyond said predetermined range, utilizing a predetermined relatively low fixed CFAR detection threshold level in place of the variable CFAR detection threshold, said fixed threshold level having a value less than about 99% of the variable CFAR detection threshold levels, and
- wherein the fixed threshold level is a function of range, weather, radio frequency interference and false targets.
Apparatus for maintaining a false rate at or below a desired rate over a fluctuating mean noise level so as to provide additional sensitivity and accordingly increased range performance in a constant false alarm rate (CFAR) circuit in a radar system comprising:
- a CFAR circuit responsive to signals received by the radar system and generating a variable CFAR detection threshold signal, a range signal of a range cell of interest, and a received energy signal of the range cell of interest;
- a source of site adjustable relatively low fixed range signals;
- a range comparator responsive to range signal inputs from said CFAR circuit and said source of fixed range signals and generating a first control signal in response to a comparison of said range signal of said cell of interest and a fixed range signal from said source of fixed range signals;
- a source of site adjustable relatively low fixed CFAR detection threshold signals;
- a circuit for determining whether a variable threshold or a fixed threshold is to be used for each scan of the radar system and generating a second control signal therefrom;
- a circuit responsive to said first and second control signals for selecting either said variable CFAR detection threshold signal from said CFAR circuit or a fixed CFAR detection threshold signal from said source of fixed threshold signals;
- and
- a signal comparator responsive to said received energy signal and a selected detection threshold signal for sensing a target in the received energy of the range cell of interest.
Dependencies are inferred from the claim text.