# US 5,703,592 A · Method and apparatus for estimating the detection range of a radar > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,703,592 A - Document ID: US5703592A - Status: Granted - Kind: A - Application number: 08/583,508 - Filed: 1996-01-05 - Granted: 1997-12-30 - Earliest claimed: 1995-01-17 - Assignees: Racal Radar Defence Systems Limited - Inventors: Simon Watts - Web page: https://patentgrep.com/patent/US5703592A ## CPC - G01S 7/2927: {by deriving and controlling a threshold value} - G01S 13/5244: {Adaptive clutter cancellation (specially adapted for airborne MTI, G01S13/5242)} - G01S 13/5246: {post processors for coherent MTI discriminators, e.g. residue cancellers, CFAR after Doppler filters} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract A method and apparatus estimate the detection range R.sub.1 of a radar in the presence of noise and clutter. The radar return signals from a range cell under test and from a plurality of surrounding range cells on either side of the range cell under test are measured. From the values of the return signals from the surrounding cells, a factor .alpha. is determined. The mean value of those signals is then multiplied to form a threshold value for determining the presence or absence of a target. A desired false alarm rate is maintained, however. A number of radar return signals sufficient substantially to average out local variations in clutter are used to determine a mean clutter value m.sub.c. A value which is a function of .alpha. and m.sub.c is output as the estimate of detection range R.sub.1. ## Claims ### Claim 1 A method of estimating a detection range R.sub.1 of a radar when noise and clutter are present comprising the steps of: measuring radar return signals from successive range cells under test, determining a factor .alpha. by which the mean value of those signals is to be multiplied to form a threshold value for determining the presence or absence of a target whilst maintaining a desired false alarm rate, determining, from a number of radar return signals sufficient substantially to average out local variations in clutter, a mean clutter value m.sub.c, and outputting as the estimate of detection range R.sub.1 a value which is a function of .alpha. and m.sub.c. ### Claim 2 (depends on 1) A method as claimed in claim 1, wherein R.sub.1 is given by ##EQU7## where k is a constant for given values of the radar antenna gain G in the direction of the target, the mean noise level m.sub.n and minimum radar cross section .sigma. of a target which is to be detectable. ### Claim 3 (depends on 2) A method as claimed in claim 2, wherein ##EQU8## where K.sub.r is a constant determined by the radar operating parameters and characteristics. ### Claim 4 (depends on 1) A method as claimed in claim 1, wherein the value of .alpha. is obtained by a process in which it is continuously adjusted by means of a feedback loop to provide said desired false alarm rate. ### Claim 5 (depends on 4) A method as claimed in claim 4, wherein the value of .alpha. is incremented by a small amount every time there is an alarm and is decremented by a larger amount at fixed intervals. ### Claim 6 (depends on 1) A method as claimed in claim 1, wherein the value of .alpha. is calculated directly from the values in the range cells. ### Claim 7 (depends on 1) A method as claimed in claim 1, and further comprising the step of measuring radar return signals from a plurality of surrounding range cells on either side of each range cell under test. ### Claim 8 (depends on 7) A method as claimed in claim 7, wherein said factor .alpha. is determined from values of said radar return signals from the surrounding range cells. ### Claim 9 An apparatus for estimating a detection range R.sub.1 of a radar when noise and clutter are present comprising: means for measuring radar return signals from successive range cells under test, means for determining a factor .alpha. by which the mean value of those signals is to be multiplied to form a threshold value for determining the presence or absence of a target whilst maintaining a desired false alarm rate, means for determining, from a number of radar return signals sufficient substantially to average out local variations in clutter, a mean clutter value m.sub.c, and means for outputting as the estimate of detection range R.sub.1 a value which is a function of .alpha. and m.sub.c. ### Claim 10 (depends on 9) An apparatus as claimed in claim 9, wherein said means for determining a factor .alpha. further comprises a feedback loop for continuous adjustment of the value of .alpha. to provide said desired false alarm rate. ### Claim 11 (depends on 10) An apparatus as claimed in claim 10, wherein said means for determining a factor .alpha. is adapted to increment the value of .alpha. every time there is an alarm and to decrement the value of .alpha. by a larger amount at fixed intervals. ### Claim 12 (depends on 9) An apparatus as claimed in claim 9, wherein said means for determining a factor .alpha. comprises means to calculate the value of .alpha. directly from the values in the range cells. ### Claim 13 (depends on 9) An apparatus as claimed in claim 9, further comprising a display adapted such that different colours are used to separate regions with different probabilities of detection for a given size of target. ### Claim 14 (depends on 9) An apparatus as claimed in claim 9, further comprising a display adapted such that regions with different probabilities of detection for a given size of target are separated by contour lines. ### Claim 15 (depends on 9) An apparatus as claimed in claim 9, wherein the means for measuring radar return signals also measures radar return signals from a plurality of surrounding range cells on either side of each range cell under test. ### Claim 16 (depends on 15) An apparatus as claimed in claim 15, wherein said factor .alpha. is determined from values of said radar return signals from the surrounding range cells.