Method for the discriminating of obstacles by means of radar, and applications
First Claim
1. A method for discriminating an obstacle among a number M of obstacles, this obstacle having a substantially plane surface, wherein said method comprises successively transmitting, from a radar, a number N greater than 2 of substantially plane waves at distinct angular frequencies ω
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i, the whole number i distinct angular frequencies ω
i, the whole number i varying from 1 to N, the N angular frequencies ω
i being chosen so as to be slightly different in a frequency band Δ
F that is narrow enough for the reflection coefficients obtained on a same obstacle for different angular frequencies to be the same, whatever may be to angular frequency, each wave at a given angular frequency ω
i being furthermore sent with tow distinct polarization p and p'"'"' chosen in such a way that only the reflection coefficients obtained for each of the polarizations on the surface of the obstacle to be discriminated, for waves at a given angular frequency reaching said surface at a normal angle of incidence, are equal, the polarizations making it thus possible to achieve a discrimination of the obstacle, demodulating response signals rip (t) and rip'"'"' (t) received by the radar and corresponding to the waves sent at the different angular frequencies ω
i with the respective polarizations p and p'"'"' so as to obtain signals Yip and Yip '"'"' independent of time; and
combining the signals Yip and Yip '"'"' in order to achieve the discrimination.
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Abstract
Disclosed is a method for the discriminating of obstacles by means of a radar, and its different applications to the measurement of a liquid in a tank or vessel, or again to the elimination of unwanted or parasitic echos coming notably from the ground, for radars mounted on vehicles or controlling vehicle traffic. To implement the method, the obstacle to be discriminated must have a substantially plane surface. The disclosed method then consists in successively transmitting substantially plane waves at slightly different angular frequencies ωi, each wave being furthermore sent with two different polarizations p and p'"'"' chosen in such a way that these different coefficients of reflection on the obstacles according to the incidence of the waves give a criterion of discrimination. The processing at reception depends on the use (measurement of distance, elimination of parasitic echos etc.). The main promising feature of the invention lies in the fact that it is possible to make very precise measurements without placing excessive constraints on the transmission pattern of the radar.
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Citations
12 Claims
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1. A method for discriminating an obstacle among a number M of obstacles, this obstacle having a substantially plane surface, wherein said method comprises successively transmitting, from a radar, a number N greater than 2 of substantially plane waves at distinct angular frequencies ω
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i, the whole number i distinct angular frequencies ω
i, the whole number i varying from 1 to N, the N angular frequencies ω
i being chosen so as to be slightly different in a frequency band Δ
F that is narrow enough for the reflection coefficients obtained on a same obstacle for different angular frequencies to be the same, whatever may be to angular frequency, each wave at a given angular frequency ω
i being furthermore sent with tow distinct polarization p and p'"'"' chosen in such a way that only the reflection coefficients obtained for each of the polarizations on the surface of the obstacle to be discriminated, for waves at a given angular frequency reaching said surface at a normal angle of incidence, are equal, the polarizations making it thus possible to achieve a discrimination of the obstacle, demodulating response signals rip (t) and rip'"'"' (t) received by the radar and corresponding to the waves sent at the different angular frequencies ω
i with the respective polarizations p and p'"'"' so as to obtain signals Yip and Yip '"'"' independent of time; and
combining the signals Yip and Yip '"'"' in order to achieve the discrimination. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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i, the whole number i distinct angular frequencies ω
Specification