Radar method and device for the measurement of distance
First Claim
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1. A method for the measurement of distance by means of a radar wherein:
- the radar is positioned so that the useful obstacle for which the distance is to be measured sends back the most powerful echo,the radar is made to transmit a sequence of non-modulated microwave signals {sk } whose discrete angular frequencies are evenly distributed in a scanned frequency band B
space="preserve" listing-type="equation">s.sub.k =u exp j(w.sub.0 +kΔ
w)t!u being a coefficient of amplitude, w0 being an initial angular frequency, Δ
w being the change in angular frequency at the passage from one signal to another, t being the time variable and k being a positive integer varying from 0 to N-1, N being the number of elements of a sequence of signals,the radar is made to demodulate the signals received in return for the transmitted signals for the generation, in video band, of a sequence of signals {rk } having the form;
##EQU12## M being an integer representing the number of useful and parasitic obstacles sending back echoes, ν
i being a coefficient of amplitude depending on the coefficient of reflexion of the ith obstacle and τ
i being the delay or time taken by the signal transmitted by the radar to go to the ith obstacle and return therefrom, the obstacle with the index 0 being the useful obstacle, andand the sequence of received and demodulated signals {rk } is processed in order to extract therefrom the value of the delay τ
0 and to deduce therefrom the distance dA from the radar to the useful obstacle by means of the relationship;
##EQU13## c being the velocity of propagation of the waves of the radar, wherein the processing of the sequence of the received signals {rk } consists of;
a discrete and reverse Fourier transform enabling a coarse temporal localization of the useful echo by the selection of the output filter giving the strongest response,an implementation of a high resolution method for the localization of radiating sources giving a temporal localization of real or fictitious echoes,a selection, in the temporal localization of echoes given by the high resolution method, of a limited temporal range centered on the selected output filter of the discrete and reverse Fourier transform, andthe making of a choice, from said limited range, of the echo giving the strongest response as being the echo of the useful obstacle and the adoption of its delay as the value of the delay τ
0,an estimation of the distance dA of the useful obstacle by means of the relationship;
##EQU14##
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Abstract
Disclosed is a method for the measurement, by means of a radar, of the distance from a useful obstacle that is surrounded by parasitic obstacles but sends back an echo which is more powerful than their echos. This method of measurement can be applied to the measuring of the level of liquid in a vessel. It consists in transmitting a sequence of non-modulated microwave signals whose discrete angular frequencies are evenly distributed in a certain frequency band, demodulating the signals received in return for the transmitted signals, subjecting the received and demodulated signals to a reverse and discrete Fourier transform with a view to a coarse localization of the delay of the echo from the useful obstacle and a high resolution method for the localization of the radiating sources with a view to a more precise localization of the delay of the echo from the useful obstacle, said delay enabling the assessment of the distance from the useful obstacle to the radar. FIG. 5.
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Citations
4 Claims
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1. A method for the measurement of distance by means of a radar wherein:
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the radar is positioned so that the useful obstacle for which the distance is to be measured sends back the most powerful echo, the radar is made to transmit a sequence of non-modulated microwave signals {sk } whose discrete angular frequencies are evenly distributed in a scanned frequency band B
space="preserve" listing-type="equation">s.sub.k =u exp j(w.sub.0 +kΔ
w)t!u being a coefficient of amplitude, w0 being an initial angular frequency, Δ
w being the change in angular frequency at the passage from one signal to another, t being the time variable and k being a positive integer varying from 0 to N-1, N being the number of elements of a sequence of signals,the radar is made to demodulate the signals received in return for the transmitted signals for the generation, in video band, of a sequence of signals {rk } having the form;
##EQU12## M being an integer representing the number of useful and parasitic obstacles sending back echoes, ν
i being a coefficient of amplitude depending on the coefficient of reflexion of the ith obstacle and τ
i being the delay or time taken by the signal transmitted by the radar to go to the ith obstacle and return therefrom, the obstacle with the index 0 being the useful obstacle, andand the sequence of received and demodulated signals {rk } is processed in order to extract therefrom the value of the delay τ
0 and to deduce therefrom the distance dA from the radar to the useful obstacle by means of the relationship;
##EQU13## c being the velocity of propagation of the waves of the radar, wherein the processing of the sequence of the received signals {rk } consists of;a discrete and reverse Fourier transform enabling a coarse temporal localization of the useful echo by the selection of the output filter giving the strongest response, an implementation of a high resolution method for the localization of radiating sources giving a temporal localization of real or fictitious echoes, a selection, in the temporal localization of echoes given by the high resolution method, of a limited temporal range centered on the selected output filter of the discrete and reverse Fourier transform, and the making of a choice, from said limited range, of the echo giving the strongest response as being the echo of the useful obstacle and the adoption of its delay as the value of the delay τ
0,an estimation of the distance dA of the useful obstacle by means of the relationship;
##EQU14## - View Dependent Claims (2, 3)
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4. A radar device for the measurement of the distance of a useful obstacle that is surrounded by parasitic obstacles and sends back an echo more powerful than those of the parasitic obstacles, comprising:
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transmission means generating a sequence of non-modulated microwave signals {sk } whose discrete angular frequencies are evenly distributed in a scanned frequency band B
space="preserve" listing-type="equation">s.sub.k =u exp j(w.sub.0 +kΔ
w)t!u being a coefficient of amplitude, w0 being an initial angular frequency, Δ
w being the change in angular frequency at the passage from one signal to another, t being the time variable and k being a positive integer varying from 0 to N-1, N being the number of elements of the sequence of signals,reception and demodulation means receiving the signals sent back as echos by useful and parasitic signals and demodulating them by the transmitted signals for the generation, in baseband, of a sequence of signals {rk } having the form;
##EQU15## M being an integer representing the number of useful and parasitic obstacles sending back echoes, ν
i being a coefficient of amplitude depending on the coefficient of reflexion of the ith obstacle and τ
i being the time taken by the transmitted signal to go from the radar to the ith obstacle and return therefrom, the obstacle with the index 0 being the useful obstacle,processing means extracting, from the sequence of received and demodulated signals {rk }, the value τ
0 of the delay of the echo from the useful obstacle and deducing therefrom the distance dA from the radar to the useful obstacle by means of the relationship;
space="preserve" listing-type="equation">d.sub.A =τ
.sub.0 ·
c/2c being the velocity of propagation of the waves of the radar, wherein said processing means comprise; means to carry out a discrete and reverse Fourier transform on the sequence of received and demodulated signals {rk }, means to select the output filter of the means for implementing the Fourier transform giving the strongest response, means to implement a high resolution method for the localization of radiating sources working on the sequence of received and demodulated signals {rk } and giving a temporal localization of real or fictitious echoes, means to limit the temporal localization of real and fictitious echoes to a limited range centered on the selected output filter of the means to implement the Fourier transform, and means to discriminate the echo giving the strongest response in the limited range of the temporal localization of echos adopting the delay of this echo as being the delay τ
0 of the useful obstacle, andmeans to estimate the distance dA of the useful obstacle by implementing the relationship;
space="preserve" listing-type="equation">d.sub.A =τ
.sub.0 ·
c/2
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Specification
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Current AssigneeThomson-CSF (Thales SA)
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Original AssigneeThomson-CSF (Thales SA)
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InventorsCrenn, Patrice, Brendle, Jean-Claude, Cornic, Pascal
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Primary Examiner(s)ELDRED, JOHN W
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Application NumberUS08/414,594Time in Patent Office368 DaysField of Search342/118, 342/124, 340/618, 340/612US Class Current342/118CPC Class CodesG01F 23/284 Electromagnetic wavesG01S 13/24 using frequency agility of ...
