Distribution sensitive constant false alarm rate (CFAR) processor

• US 4,586,043 A
• Filed: 03/21/1984
• Issued: 04/29/1986
• Est. Priority Date: 03/21/1984
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Wolf, Mary L.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Hayes, D.
• Application Number:
  US06/592,036
• Time in Patent Office: 769 Days
• Field of Search: 343/5 R, 343/5 CF, 343/7 A, 343/5 VQ, 343/5 CE
• US Class Current: 342/93
• CPC Class Codes: G01S 7/2923 based on data belonging to a number of consecutive radar periods

Abstract

In a radar receiver, a distribution sensitive constant false alarm rate processor derives the clutter threshold level from the average magnitude of echo return signals. The threshold level continuously adjusts to the changing conditions of the radar environment and correctly corresponds to the false alarm rates which may be varied by the user of the host radar system. The clutter threshold is then used to suppress clutter returns following either a Rayleigh distribution or a Weibull distribution.

Claims

1. A false alarm control system for eliminating clutter echo return signals corresponding to selectable false alarm rates and responsive to changing clutter conditions in the radar environment comprising:

a signal splitter receiving radar video signals from a host radar system and outputting first and second sets of radar video signals;

a constant false alarm rate processor receiving said first set of radar video signals and calculating the clutter threshold level, said clutter threshold level responsive to changing clutter conditions in the radar environment and corresponding to selectable false alarm rates, said constant false alarm rate processor comprises a data processing system sorting said radar video signals received from said signal splitter by magnitude of the echo return signals of each cell, said data processing system performing first and second cell averaging calculations for a subset of said radar video signals, said data processing system performing said clutter threshold calculation in terms of said selectable false alarm rate and said first and second cell averaging calculations, said constant false alarm rate processor performs said clutter threshold calculation defined by the equation;

##EQU12## such that T equals the value of said clutter threshold,

P equals said selectable false alarm rate,

X₁ and X₂ equals the value of said first and second cell averaging calculation, and K₁ and K₂ equal the values given by ##EQU13## where c₁ and c₂ equals the number of cells used in said first and second cell averaging calculations;

a delay circuit receiving said second set of radar video signals from said signal splitter said delay circuit delaying said second set of radar video signals while said clutter threshold level is being calculated by said constant false alarm rate processor;

and a compare circuit receiving said second set of radar video signals from said delay circuit and said clutter threshold level from said constant false alarm rate processor, said compare circuit passing on to a display processor of said host radar system the set of said radar video signals whose magnitudes exceed said clutter threshold.