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Doppler correlation radar providing combined target detection and ranging

  • US 3,882,494 A
  • Filed: 06/11/1973
  • Issued: 05/06/1975
  • Est. Priority Date: 06/11/1973
  • Status: Expired due to Term
First Claim
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1. In a moving target correlation radar system of the type comprising means for transmitting a continuous carrier wave modulated with a predetermined encoded modulating signal including a pseudo-random code sequence, means for demodulating echo signals received from any moving target within a given range illuminated with said transmitted signal, range-bins switch means for selectively deriving a delayed pseudo-random code sequence having a delay corresponding to any one of a plurality of different range bins, means coupled to said range-bins switch for generating a decoding signal including a pseudo-random code sequence manifesting the delay selected by said range-bins switch, and doppler-frequency means including correlation decoding means for correlating said demodulated echo signals against said decoding signal to derive an output signal from said correlation decoding means which includes the doppler-frequency signature signal of a moving target having a range within the range bin selected by said range bins switch means;

  • the improvement wherein;

    said transmitting means is arranged to provide a cyclic encoded modulating signal, each cycle of said encoded modulating signal including at least one detection portion and one range bins portion which occur serially with respect to each other, said pseudo-random code sequence occurring only during said rangebins portion, said encoded modulating signal having a first format during a detection portion thereof, and said decoding signal generating means is arranged to provide a cyclic decoding signal, each cycle of said decoding signal including at least one detection portion and one range-bins portion which occur serially with respect to each other in predetermined phase relationship with respect to said detection portion and range-bins portion of said encoded modulating signal, said delayed pseudo-random sequence only occurring during said range-bins portion of said decoding signal, and said predeterMined phase relationship providing a cooperative relationship in which said delayed pseudo-random code sequence has an appreciable correlation with the pseudo-random sequence during said range-bins portion of said encoded modulating signal as manifested in said demodulated echo signals only when said moving target has a range within the range bin selected by said range-bins switch, said detection portion of said decoding signal having a second format cooperatively related to said first format of said detection portion of said encoded modulating signal so that with said predetermined phase relationship there is provided a partial but significant amount of correlation during said detection portion of said decoding signal when said moving target has a range within any of said plurality of different range bins, whereby the output from said correlation decoding means includes a relatively-low amplitude doppler-frequency signature signal of a moving target having a range within a given one of the range bins when said given one of said range bins is not selected by said range-bins switch and includes a relatively high-amplitude doppler-frequency signature signal of that moving target when said given one of said range bins is selected by said range-bins switch.

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