GB2265515A - Method of enhancing the target : clutter ratio in a radar return - Google Patents

Method of enhancing the target : clutter ratio in a radar return Download PDF

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Publication number
GB2265515A
GB2265515A GB9209039A GB9209039A GB2265515A GB 2265515 A GB2265515 A GB 2265515A GB 9209039 A GB9209039 A GB 9209039A GB 9209039 A GB9209039 A GB 9209039A GB 2265515 A GB2265515 A GB 2265515A
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GB
United Kingdom
Prior art keywords
target
block
radar
enhancing
scattering
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9209039A
Other versions
GB9209039D0 (en
GB2265515B (en
Inventor
Montague Ralph Gilday
Gerald Norman Jepps
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EMI Group Electronics Ltd
Original Assignee
Thorn EMI Electronics Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB919108945A external-priority patent/GB9108945D0/en
Application filed by Thorn EMI Electronics Ltd filed Critical Thorn EMI Electronics Ltd
Priority to GB9209039A priority Critical patent/GB2265515B/en
Publication of GB9209039D0 publication Critical patent/GB9209039D0/en
Publication of GB2265515A publication Critical patent/GB2265515A/en
Application granted granted Critical
Publication of GB2265515B publication Critical patent/GB2265515B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/414—Discriminating targets with respect to background clutter
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/024—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using polarisation effects

Abstract

In a scattering matrix radar system the scattering matrices for a set of range-doppler radar cells are calculated (block 4). The 2N minimum or null co-polarizations are calculated from the matrices corresponding to N reference cells (block 8) and used to respectively polarization-filter the scattering matrix corresponding to a target cell (block 10) to give 2N output powers for the target cell. These 2N output powers are summed (block 12) and the result is compared with a threshold (block 14) for target detection. The invention relies on the fact that clutter and target have different polarization characteristics. <IMAGE>

Description

METHOD OF ENHANCING THE TARGET:CLUTTER RATIO IN A RADAR RETURN This invention relates to a method of enhancing the target: clutter ratio in a radar return.
In one such method known from a paper "Virtual Polarization Adaptation" by A.J. Poelmann in Proc. IEE, Volume 128 part F No.5 (October 1981) at page 261 et seq. the average scattering matrix of a plurality of radar cells situated within a "window" which includes a target radar cell is measured, a polarization filter is derived from the average scattering matrix, and the return from a target radar cell is subjected to said polarization filter. This known method has been found to be insufficiently robust in many circumstances and it is an object of the present invention to enable an improvement to be obtained in this respect.
The invention provides a method of enhancing the target:clutter ratio in a radar return, comprising the steps of: (a) measuring the scattering matrices of a plurality of reference radar cells; (b) deriving respective polarization filters from said scattering matrices; (c) subjecting the return from a target radar cell to each of said polarization filters, and (d) combining the results of step (c).
It has now been found that the robustness of the known method can be significantly improved if, rather than measuring merely the average scattering matrix of a plurality of radar cells situated within the window and deriving a polarization filter from this average, the scattering matrix of each cell of the plurality is measured individually, a respective polarization filter is derived from each matrix thus measured, the return from the target radar cell is subjected to each polarization filter tSus derived, and the results of this are combined.
Because two minimum or null co-polarizations (common transmitter/receiver polarization pairs for which minimum or zero signal is received) occur for each return, preferably but not necessarily a pair of polarization filters is derived from each said scattering matrix.
Preferably but not necessarily said plurality of reference radar cells does not include said target radar cell.
An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing which is a flow diagram thereof.
In the diagram, block 2 denotes the reception of reflected radar signals by a scattering matrix radar system. Block 4 denotes the processing of these signals in known manner to provide output signals representative of the scattering matrices for individual cells (e.g. range/doppler cells). Block 6 denotes the selection of the scattering matrices of a target cell and N reference cells. Block 8 denotes the computation of the two minimum or null co-polarizations for each of the N reference cells from the corresponding scattering matrices (giving 2N outputs). Block 10 denotes the use of the 2N outputs to individually polarization filter the scattering matrix of the target cell to produce (synthesize) 2N outputs with minimum or null co-polarizations.Block 12 denotes the summing of the 2N outputs (2N signal powers) from block 10 and block 14 denotes the comparison of the result of block 12 with a threshold for target detection. Finally, line 16 denotes a return to block 6 to ensure continuation of a search for a target should one not be detected in block 14.
In the ideal situation in which all of the clutter null co-polarization pairs are identical, the clutter component from the candidate target cell would be zero, and the accepted target power would be multiplied by the number of nulls (e.g. if eight adjacent range-doppler cells are used as the reference, the accepted target power would be multiplied by sixteen). Where the clutter null pairs are not all the same, the performance of the technique will be governed by the similarity of the clutter null pairs and their dissimilarity from the corresponding target null co-polarization pair.
Although the invention has been described above with reference to a specific embodiment, it will be appreciated that it is intended to cover all modifications and equivalents within the scope of the invention as defined by the claims. For example there may be different choices for the reference clutter set. In a scanning radar, for example, the reference set could be the successive scattering matrix measurements made during the scan, or the measurements made during a previous scan. In either case it may or may not include the scattering matrix for the target cell.
Obviously, although both null or minimum co-polarization pairs for each reference cell are used in the synthesis step denoted by block 10 this is not essential; only one pair for each reference cell may be employed if desired.

Claims (4)

1. A method of enhancing the target:clutter ratio in a radar return, comprising the steps of: (a) measuring the scattering matrices of a plurality of reference radar cells; (b) deriving respective polarization filters from said scattering matrices; (c) subjecting the return from a target radar cell to each of said polarization filters, and (d) combining the results of step (c).
2. A method as claimed in Claim 1 wherein, in step (b), a pair of polarization filters is derived from each said scattering matrix.
3. A method as claimed in Claim 1 or Claim 2, wherein said plurality of reference radar cells does not include said target radar cell.
4. A method of enhancing the target:clutter ratio in a radar return, substantially as described herein with reference to the drawing.
GB9209039A 1991-04-26 1992-04-27 Method of enhancing the target:clutter ratio in a radar return Expired - Fee Related GB2265515B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9209039A GB2265515B (en) 1991-04-26 1992-04-27 Method of enhancing the target:clutter ratio in a radar return

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB919108945A GB9108945D0 (en) 1991-04-26 1991-04-26 Radar system
GB9209039A GB2265515B (en) 1991-04-26 1992-04-27 Method of enhancing the target:clutter ratio in a radar return

Publications (3)

Publication Number Publication Date
GB9209039D0 GB9209039D0 (en) 1993-07-14
GB2265515A true GB2265515A (en) 1993-09-29
GB2265515B GB2265515B (en) 1995-02-01

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB9209039A Expired - Fee Related GB2265515B (en) 1991-04-26 1992-04-27 Method of enhancing the target:clutter ratio in a radar return

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0752597A1 (en) * 1995-07-07 1997-01-08 Thomson-Csf Polarimetric detection processing circuit for a radar receiver

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108919206B (en) * 2018-07-18 2022-03-04 武汉大学 External radiation source radar polarization filtering method based on subcarrier processing

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987007389A2 (en) * 1986-05-27 1987-12-03 Hughes Aircraft Company Adaptive radar for reducing background clutter
US4829303A (en) * 1988-05-18 1989-05-09 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Data volume reduction for imaging radar polarimetry

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987007389A2 (en) * 1986-05-27 1987-12-03 Hughes Aircraft Company Adaptive radar for reducing background clutter
US4829303A (en) * 1988-05-18 1989-05-09 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Data volume reduction for imaging radar polarimetry

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0752597A1 (en) * 1995-07-07 1997-01-08 Thomson-Csf Polarimetric detection processing circuit for a radar receiver
FR2736438A1 (en) * 1995-07-07 1997-01-10 Thomson Csf POLARIMETRIC DETECTION PROCESSING CIRCUIT FOR RADAR RECEIVER
US5764182A (en) * 1995-07-07 1998-06-09 Thomson-Csf Polarimetrical processing detection circuit for radar receiver

Also Published As

Publication number Publication date
GB9209039D0 (en) 1993-07-14
GB2265515B (en) 1995-02-01

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Legal Events

Date Code Title Description
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19970427