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System for detection of objects with given, known characteristics against a background

  • US 4,829,306 A
  • Filed: 08/31/1987
  • Issued: 05/09/1989
  • Est. Priority Date: 08/31/1987
  • Status: Expired due to Term
First Claim
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1. A system for the detection of objects with given, known characteristics against a background, comprising a transmitter means for transmitting one of either electromagnetic or acoustic waves having characteristics adapted for the objects to be detected or correspondingly adapted to suppress the background prior to the detection of the objects, said waves being composed of a number of coherent frequency components whose frequency is a function of time, and a receiver means for receiving backscattered electromagnetic or acoustic waves and for coherent demodulation using signal adaptive filters and comprising more than one homodyne detector, wherein at least one of said transmitter means and said receiver means comprise at least two apertures for coherent transmission or reception of the waves and wherein a distance between said at least two apertures is larger than one wavelength of the transmitted waves, and wherein signals derived from the received waves by said demodulation and filtering, and related to at least two simultaneously transmitted frequencies and at least two apertures respectively, undergo complex multiplication, wherein a signal detected by one of said more than one homodyne detectors at one frequency and at one of said at least two apertures, is subjected to said complex multiplication with another signal detected by another of said more than one homodyne detectors at another simultaneously transmitted frequency at another of said at least two apertures separated from said one aperture by at least one wavelength of said waves, said complex multiplication providing a product which constitutes a matched filter for a given object or background.

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