Communications: directive radio wave systems and devices (e.g. – With particular circuit – Spectrum analysis
Patent
1987-05-21
1991-02-12
Tarcza, Thomas H.
Communications: directive radio wave systems and devices (e.g.,
With particular circuit
Spectrum analysis
342190, 342 64, 342 90, G01S 13526
Patent
active
049927973
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention is primarily directed to an improved radar for detecting and identifying remote objects or targets by means of electromagnetic wave energy. The method and principles to be described may also be applied, however, to other types of wave energy, such as ultrasonic waves in sonar systems.
As in known radar systems the present method involves the utilization of various processing techniques for extracting useful information from the return signal or waves reflected from the target.
The radar system described here provides optimum detection and identification of targets while minimizing the effect of background clutter and the impairments caused by the propagation of the electromagnetic waves through space.
This is achieved utilizing a set of new concepts for signal processing, the applicability of which is made feasible by the development of new technology for generating microwaves and in particular digital signal processing.
SUMMARY OF THE INVENTION
Thus, in a main aspect this invention relates to a method of detection and identification of one or more remote objects by transmitting wave energy towards the object and receiving wave energy reflected from the object as well as processing of information associated with the wave energy received. The following novel and specific combination of steps is characteristic to the method according to the invention
(a) said processing comprises a number of separate signal parameters pertaining to the wave energy received, said parameters together forming a measured signature relating to the object,
(b) the measured signature is compared with a number of prestored signatures comprising the same separate signal parameters relating to known objects being of interest to the detection and the identification,
(c) there is effected a recording of which signatures among the prestored signatures which within predetermined tolerances correspond to the measured signature,
(d) subsequent transmission and reception of wave energy is used for updating the separate parameters and thereby the measured signature,
(e) the updated measured signature is compared with the recorded restored signatures for updated recording of a smaller number of prestored signatures which within predetermined tolerances correspond to the updated measured signature,
(f) and repeating steps (d) and (e) until there remains a small number of recorded prestored signatures, preferably only one such signature, which defines a small number of objects, preferably only one such object, being of interest.
In order to obtain a number of separate signal parameters adequate for processing as stated above, it is an advantage to use a multifrequency radar signal transmission. More specifically, multifrequency polarimetric illumination of targets makes it possible to determine characteristics of target signatures. With multifrequency illumination several independent feature or signal parameter domains of the targets are revealed. In other words this involves the simultaneous use of orthogonal signatures for identification of targets or objects of interest.
Such parameters or feature domains may be the following: (target down-range signature), multifrequency response (vibration pattern),
As each of these parameter sets (domains) are independent and thus mathematically orthogonal, a multidimensional target estimation is performed.
Among the parameter domains mentioned above, the multifrequency illumination response is considered to be fundamental. In addition thereto, the polarization properties associated with possible target symmetry may be very useful.
The aspect angle of target as seen from the radar location at any instant is also an important magnitude which could to some extent be considered as one of the separate signal parameters referred to. In this context, however, the aspect angle is treated as a variable different from the types of signal parameters in the domains as listed above (i . . . v).
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration of a preferred
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Gjessing Dag K. T.
Hjelmstad Jens F.
Norges Teknisk-Naturvitenskapelige Forskningsrad
Sotomayor John B.
Tarcza Thomas H.
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