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Radar method and device for the measurement of distance

  • US 5,504,490 A
  • Filed: 03/31/1995
  • Issued: 04/02/1996
  • Est. Priority Date: 04/05/1994
  • Status: Expired due to Fees
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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