System and Method of Radar Location

• US 20130234878A1
• Filed: 02/22/2013
• Published: 09/12/2013
• Est. Priority Date: 02/24/2012
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Kemkemian, Stphane, Artis, Jean-Paul, Quellec, Jean-Michel
• Granted Patent: US 9,035,824 B2
• Time in Patent Office: Days
• US Class Current: 342/18
• CPC Class Codes: G01S 13/06 Systems determining position data of a target
• CPC Class Codes: G01S 13/103 particularities of the measurement of the distance G01S13/12, G01S13/14, G01S13/16, G01S13/18 and G01S13/20 take precedence
• CPC Class Codes: G01S 13/282 using a frequency modulated carrier wave G01S13/286 takes precedence
• CPC Class Codes: G01S 7/285 Receivers
• CPC Class Codes: G01S 7/2921 based on data belonging to one radar period
• CPC Class Codes: G01S 7/36 Means for anti-jamming , e.g. ECCM, i.e. electronic counter-counter measures

Abstract

A system and method of radar location comprises radar signal emission means, an emitted pulse of duration T1 and index i starting at instant T2(i); means receiving reflected radar signals; means determining correlation between reconstruction of an emitted pulse and signal received during the time interval between T2(i)+2*T1 and T2(i+1). The means determining a correlation can reconstruct a set, of at least one truncated pulse j of duration T3(j), less than T1, corresponding to the final part of said emitted pulse, said truncated pulses having increasing respective durations, determining at least one first correlated signal j by correlation of said truncated pulse j and signal received during time interval between T2(i)+T1 and T2(i)+T1+T3(j) and determining a second signal, based on first correlated signals j, by copying the time interval, of said correlated signal j, between T2(i)+T1+T3(j) and T2(i)+T1+T3(j+1), onto the time interval, of said second signal, between T2(i)+T1+T3(j) and T2(i)+T1+T3(j+1).

Claims

1. A system for radar location comprising:

radar signal emission means, said signal comprising at least one emitted pulse, an emitted pulse having a duration T1 and an associated index i and starting at an instant T2(i), moreover the said pulse being modulated by at least one code preserving good autocorrelation properties when a fraction of the said code is used;

means for receiving reflected radar signals;

means for determining a correlation between a reconstruction of an emitted pulse and the radar signal received during the time interval starting at T2(i)+2*T1 and finishing at T2(i+1);

said means for determining a correlation being further adapted for;

reconstructing a set, of at least one truncated pulse j, a truncated pulse j being of duration T3(j), smaller than the duration of the emitted pulse T1 and corresponding to the final part of the said emitted pulse, said truncated pulses being of increasing respective durations,

determining at least one first correlated signal j by correlation of said truncated pulse j and of the signal received during the time interval starting at T2(i)+T1 and finishing at T2(i)+T1+T3(j),

determining a second signal, on the basis of all or part of the first correlated signals j, by copying the time interval, of said correlated signal j, starting at T2(i)+T1+T3(j−

1) and finishing at T2(i)+T1+T3(j), onto the time interval, of said second signal, starting at T2(i)+T1+T3(j−

1) and finishing at T2(i)+T1+T3(j).

2. The system according to claim 1, in which said means for determining a correlation are furthermore adapted for multiplying the temporal samples of the said truncated pulses by a respective weighting coefficient belonging to a weighting window.

3. The system according to claim 1, in which said means for determining a correlation are further adapted, on the basis of a reconstructed pulse j, for:

computing a first vector corresponding to the discrete Fourier transform of the signal received on the interval from T2(i)+T1 to T2(i)+T1+T3(j),

determining a second vector corresponding to the discrete Fourier transform of the time reversal of the complex conjugate of the reconstructed pulse j, and

computing said first correlated signal j by inverse discrete Fourier transform of the term-by-term multiplication of the first and of the second vector.

4. The system according to claim 1, in which said emission means are further adapted for the emission of radar signals comprising at least one pulse modulated by using a linear or nonlinear frequency ramp and said reception module is adapted for the reception of radar signals comprising said pulses modulated by using a linear or nonlinear frequency ramp.

5. The system according to claim 4, in which said means for determining a correlation are further adapted, on the basis of a reconstructed pulse j, for filtering the samples of said second signal, over an interval starting at T2(i)+T1+T3(j) and finishing at T2(i)+T1+T3(j+1) so that a sample of said interval is equal to the weighted average of the neighbour samples of said sample.

6. The system according to claim 1, in which said emission means are adapted for using a set of different frequencies for the emission of the said pulses of said radar signals and said reception means are adapted for receiving said pulses of said reflected radar signals on said different frequencies.

7. The system according to claim 6;

further comprising means for determining a third synchronization signal, for an emitted pulse i using a frequency, by the term-by-term addition, for all or some of the emitted pulses j using the same frequency, of the samples of the interval of said reflected radar signal starting at T2(j)+T1 and finishing at T2(j)+2*T1, said addition being stored in the time interval, of said third signal, starting at T2(i)+T1 and finishing at T2(i)+2*T1;

said means for determining a correlation being further adapted for the correlation between the reconstruction of an emitted pulse and the time interval, of said third signal, starting at T2(i)+2*T1 and finishing at T2(i+1).

8. A method of radar location using the system according to claim 7 comprising the following steps:

detecting a possible jamming source,

in the case of non-detection of a jamming source, emitting and receiving a radar signal for which the pulses forming part of one and the same group of successive pulses use an identical emission frequency, the emission frequency varying from one group to the next, and

in the case of detection of a jamming source, emitting and receiving a radar signal using different frequencies for two successive pulses, the frequencies following a periodic or nonperiodic distribution law.