Method of assessing radar target pulses

• US 5,323,161 A
• Filed: 07/13/1989
• Issued: 06/21/1994
• Est. Priority Date: 08/29/1986
• Status: Expired due to Fees

• Current Assignee: MBDA UK Ltd. (MBDA SAS)
• Original Assignee: Marconi Holdings Company Limited
• Inventors: Winstone, Martin R., Gailer, James M.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US07/382,974
• Time in Patent Office: 1,804 Days
• Field of Search: 342/13, 342/16, 342/17, 342/159
• US Class Current: 342/13
• CPC Class Codes: G01S 7/021 Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals
• CPC Class Codes: G01S 7/2923 based on data belonging to a number of consecutive radar periods

Abstract

A method of assessing radar pulses in a passive, i.e. receive-only, radar system to distinguish pulses due to a particular target from pulses due to other targets from noise, interference, etc. Received pulses are assessed, without reference to pulse transmission information, in respect of a number of characteristics by comparing each characteristic of a pulse with the mean value of the respective characteristic for pulses previously received. Using a probability process, confidence values for the pulse can be calculated. By combining the confidence values for each characteristic, an overall confidence value is obtained for the pulse so that it can be determined whether it arises from the particular target.

Claims

1. A method of assessing target radar pulses received by an antenna of a passive radar receiver in respect of a plurality of pulse characteristics comprising the steps of:

(a) determining value of at least two said characteristics for a received pulse;

(b) determining the mean value of each said characteristic for previously received pulses;

(c) comparing the value of each said characteristic for a pulse with said mean value and deriving an increment;

(d) subjecting each said increment to a probability process to provide a confidence value for each pulse characteristic;

(e) combining the confidence values for said at least two characteristics to provide an overall confidence value for said pulse; and

(f) performing all of said steps without reference to pulse transmission information.

2. A method according to claim 1 in which said plurality of pulse characteristics comprises at least to of:

the target angle, the pulse power level, the pulse width and the pulse repetition interval.

3. A method according to claim 1 in which said plurality of pulse characteristics comprises the target angle and at least one of:

the pulse power level, the pulse width and the pulse repetition interval.

4. A method according to claim 3 in which said probability process to provide a confidence value for said target angle takes account of an estimated thermal noise component of the received pulse.

5. A method according to claim 3 in which said target angle comprises the angle between the target and the antenna boresight and is derived from measured values of the target angle in azimuth and elevation.

6. A method according to claim 5 in which a mean value of the target angle is derived from mean values of the azimuth and elevation target angles.

7. A method according to claim 1 in which the confidence value in respect of at least one of said pulse characteristics is subjected to a respective weighting factor responsive to predetermined uncertainty in the particular characteristic value.

8. A passive radar receiver including pulse assessment circuitry for distinguishing a target signal from other radar transmission, without recourse to pulse transmission information, said circuitry comprising:

(a) means in respect of each of a plurality of pulse characteristics for determining the current value of the respective characteristic;

(b) means for determining the mean value of said respective characteristic for previously received pulses;

(c) means for comparing said current value of each said characteristic with said mean value and deriving an incremental difference;

(d) means for subjecting each said incremental difference to a probability process based on factors exclusive of prior information concerning radar emissions from the target, and for producing a confidence value for each pulse characteristic in respect of the current pulse being an emission from said target; and

(e) means for combining the confidence values produced in respect of each of said pulse characteristics of said current pulse to produce an overall confidence value in respect of said current pulse.