Radar imaging method, and radar using such a method

Patent metadata

Field	Value
Publication number	US-12436269-B2
Application number	US-202117920718-A
Country	US
Kind code	B2
Filing date	Apr 16, 2021
Priority date	Apr 29, 2020
Publication date	Oct 7, 2025
Grant date	Oct 7, 2025

Abstract

An imaging method using a doppler radar wherein the pointing direction in transmission (d ei ) is modified from recurrence to recurrence; each detection block of duration T comprises a periodic repetition of a number C of pointing cycles, each of these cycles comprising a number P of recurrences, the set of these P recurrences covering the D e pointing directions (d ei ) of the set; the order of the pointings is modified in a pseudo-random manner from pointing cycle to pointing cycle during a same detection block so as to create an irregular time interval between two pointings in a same direction; at least one beam is formed in reception on each recurrence in a direction included in the transmission-focused angular domain in the pointing direction corresponding to the recurrence.

First claim

The invention claimed is:

1. An imaging method using a doppler radar using an active antenna comprising N transmission channels and M reception channels, said antenna covering an angular domain of given solid angle during a detection time interval of duration T, said time unit corresponding to a detection block wherein the N transmission channels are focused successively in pointing directions (d ei ) taken from a set of D e pointing directions, wherein
the pointing direction on transmission (d ei ) is modified from recurrence to recurrence;
each detection block of duration T comprises a periodic repetition of a number C of pointing cycles on transmission, each of these cycles comprising a number P of recurrences, the set of these P recurrences covering the D e pointing directions (d ei ) of said set;
the order of the pointings is modified in a pseudo-random manner from pointing cycle to pointing cycle during a same detection block on transmission so as to create an irregular time interval between two pointings in a same direction;
at least one beam is formed in reception on each recurrence in a direction included in said focused angular domain in transmission in the pointing direction corresponding to said recurrence.

2. The method as claimed in claim 1 , wherein in reception, a coherent doppler processing is performed by applying, in each pointing direction (d ei ), to all of the sampled received signals, a correlator in the doppler domain, this correlator being matched to an irregular time sampling comb corresponding to the pointing instants on transmission in a same direction.

3. The method as claimed in claim 2 , wherein the domain of application of said correlator corresponds to the domain of the relative speeds expected between the carrier of said radar and of the targets to be detected.

4. The method as claimed in claim 2 , wherein said correlator is used to eliminate the doppler ambiguities.

5. The method as claimed in claim 2 , wherein said correlator is produced by linear filtering in the time domain.

6. The method as claimed in claim 2 , wherein said correlator is produced by digital Fourier transform in the time domain.

7. The method as claimed in claim 2 , wherein said correlator is produced by digital Fourier transform in the frequency domain.

8. The method as claimed in claim 2 , wherein said correlator is used to estimate the relative speed of fixed clutter and echoes in each pointing direction, without external means for measuring the carrier speed.

9. The method as claimed in claim 8 , wherein the estimation of the speed of the fixed clutter in a given direction is obtained by integrating the energy on the distance cells relative to this direction for each doppler cell of said correlator, then in searching for the doppler cell in which the total energy is maximum.

10. The method as claimed in claim 9 , wherein said estimation of the speed of the fixed clutter is obtained by excluding the spot echoes having an echo level that exceeds a threshold.

11. The method as claimed in claim 2 , wherein said correlator is used to eliminate, in each pointing direction, fixed echoes and clutter for which the direction of arrival is different from the pointing direction.

12. The method as claimed in claim 2 , wherein said correlator is used to estimate the relative speed of the moving targets in each pointing direction.

13. The method as claimed in claim 2 , wherein said correlator is applied piecewise by breaking down the antenna into different quadrants.

14. The method as claimed in claim 1 , wherein there is established, for each beam formed in transmission and in reception, a two-dimensional map representing fixed echoes received on the distance axes for all the transmission and reception pointing values.

15. A doppler radar, capable of implementing the method as claimed in claim 1 .

16. The doppler radar as claimed in claim 15 , wherein of FMCW type.

Assignees

• Thales Sa

Inventors

• Cornic Pascal
• Le Gall Renan
• Audic Yves

Classifications

• G01S13/584

  adapted for simultaneous range and velocity measurements · CPC title

• G01S7/354

  Extracting wanted echo-signals (Doppler systems G01S13/50) · CPC title

• G01S7/356

  involving particularities of FFT processing · CPC title

• G01S7/2883

  using FFT processing · CPC title

• G01S2013/0272

  Multifunction radar · CPC title