Method for measuring the height of a target relative to the ground using a moving radar, and radar implementing such a method

Patent metadata

Field	Value
Publication number	US-10585183-B2
Application number	US-201715649374-A
Country	US
Kind code	B2
Filing date	Jul 13, 2017
Priority date	Aug 2, 2016
Publication date	Mar 10, 2020
Grant date	Mar 10, 2020

Abstract

Radar equipped with a transmission antenna array and with a reception antenna array is provided, the measurement of the height h2 is obtained by estimating the frequency of at least one time-dependent amplitude modulation produced on the reception antenna array, the modulation generated by the interference of the signals received directly from the target and the signals received after reflection on the ground, on the basis of the signals transmitted by the transmission antenna array.

First claim

The invention claimed is:

1. A method for measuring a height of a target relative to the ground comprising: using a moving radar transmitting a detection signal towards said target, equipping said radar with a transmission antenna array and with a reception antenna array that produces at least one time-dependent amplitude modulation, obtaining a measurement of a target height (h 2 ) by estimating a frequency of the at least one time-dependent amplitude modulation produced on said reception antenna array, and generating said at least one time-dependent amplitude modulation by interference of signals received directly from said target and signals received after reflection on the ground, on a basis of signals transmitted by said transmission antenna array.

2. The method according to claim 1 , wherein the measurement of said target height (h 2 ) is obtained, for a given time-dependent modulation, by applying the following equation:

h
2

=

λ
⁢

⁢

d
0
2

⁢

f
^

h
1

⁢
V

h 2 being an said estimated height;
{circumflex over (f)} being the estimated frequency of a time-dependent amplitude modulation;
h 1 being the height at which said detection signal is transmitted;
d 0 being a distance from said radar to the target;
V being a closing speed of said radar towards the target; and
λ being a wavelength of said radar.

3. The method according to claim 1 , wherein said reception antenna array being formed of one or more reception sub-arrays and said transmission antenna array being formed of one or more transmission sub-arrays, each signal transmitted by a transmission sub-array generating a time-dependent amplitude modulation on each reception sub-array, a measurement of said target height (h 2 ) is carried out by estimating a frequency of the time-dependent amplitude modulation produced on a reception sub-array by a transmission sub-array situated at the same height.

4. The method according to claim 3 , wherein the estimation ({circumflex over (f)}) of a modulation frequency is carried out using a suitable two-dimensional correlation function, taking account of the frequency and a phase at an origin of said modulation, the estimation of the frequency being equal to a frequency f k of the frequency-phase pair (f k , φ k ) giving the correlation maximum.

5. The method according to claim 1 , wherein, said reception antenna array being formed of one or more reception sub-arrays and said transmission antenna array being formed of one or more transmission sub-arrays, each signal transmitted by a transmission sub-array generating a time-dependent amplitude modulation on each reception sub-array, a measurement of said target height (h 2 ) is carried out by estimating the frequency of the time-dependent amplitude modulation produced on a reception sub-array by a transmission sub-array situated at a different height, said modulation being a product of a modulation corresponding to an outbound path and a modulation corresponding to a return path of the wave transmitted by said transmission sub-array, a measurement of said height being the estimation {circumflex over (f)} e of a modulation frequency due to the outbound path or the estimation {circumflex over (f)} r of the modulation frequency due to the return path.

6. The method according to claim 5 , wherein said measurement is taken to be equal to a combination of the estimation {circumflex over (f)} e of the modulation frequency due to the outbound path and of the estimation {circumflex over (f)} r of the modulation frequency due to the return path.

7. The method according to claim 6 , wherein said combination averages the two estimations {circumflex over (f)} e and {circumflex over (f)} r .

8. The method according to claim 5 , wherein the estimation of modulation frequencies, due to the outbound path and to the return path, is carried out using a correlation function taking account of the modulation frequency due to the outbound path and the modulation frequency due to the return path, said estimated frequencies {circumflex over (f)} e , {circumflex over (f)} r being those giving the correlation maximum.

9. The method according to claim 1 , wherein said frequency estimation with which said height measurement is obtained is a combination of time-dependent amplitude modulation frequency estimations obtained for various pairs of transmission and reception sub-arrays.

10. The method according to claim 1 , wherein, said reception antenna array including a plurality of reception sub-arrays, each reception sub-array receiving at least one interference signal originating from a signal transmitted by said transmission antenna array, said interference signal being subjected to time-dependent amplitude modulation:
a trend of at least one amplitude modulation produced along said reception antenna array at a given instant depending on the height of said sub-arrays is captured; and
an estimation {circumflex over (f)} of the time-dependent amplitude modulation frequency is calculated by means of a spatio-temporal correlation function taking account of the time-dependent amplitude modulation frequency and the frequency of at least one spatial amplitude modulation, a frequency f k corresponding to the correlation maximum of said spatio-temporal correlation being the estimated frequency {circumflex over (f)}, the measurement of said target height being calculated on a basis of this estimated frequency.

11. The method according to claim 10 , wherein, said transmission antenna array including a plurality of transmission sub-arrays, the trend of the spatial amplitude modulation produced on said reception antenna array corresponding to each signal transmitted by a transmission sub-array is captured, an estimation {circumflex over (f)} of the time-dependent amplitude modulation frequency is calculated for each transmitted signal by means of a spatio-temporal correlation function taking account of the time-dependent amplitude modulation frequency and the frequency of said at least one spatial amplitude modulation, the frequency f k corresponding to the correlation maximum of said spatio-temporal correlation being the estimated frequency {circumflex over (f)} of the time-dependent amplitude modulation generated by said transmitted signal, a measurement of said target height (h 2 ) being calculated on a basis of at least one estimated frequency corresponding to a signal transmitted from said transmission sub-arrays.

12. The method according to claim 11 , wherein the measurement of said target height (h 2 ) is a combination of the height measurements corresponding to each transmitted signal.

13. The method according to claim 12 , wherein said combination is an average.

14. The method according to claim 1 , wherein said target is a bridge deck.

15. The method according to claim 1 , wherein said target height (h 2 ) corresponds to an apparent height of a

Assignees

• Thales Sa

Inventors

• Cornic Pascal
• Audic Yves
• Kemkemian Stéphane

Classifications

• G01S2013/462

  using multipath signals · CPC title

• G01S2013/93271

  in the front of the vehicles · CPC title

• G01S13/931

  of land vehicles · CPC title

• G01S13/46 Primary

  Indirect determination of position data · CPC title

• G01S13/60 Primary

  wherein the transmitter and receiver are mounted on the moving object, e.g. for determining ground speed, drift angle, ground track (G01S13/64 takes precedence) · CPC title