Communications: directive radio wave systems and devices (e.g. – Transmission through media other than air or free space
Reexamination Certificate
1999-12-29
2003-12-02
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Transmission through media other than air or free space
C342S027000, C324S332000, C343S793000
Reexamination Certificate
active
06657577
ABSTRACT:
The present invention generally relates to a technique for detection of objects in the ground by means of ground radars. More specifically, the invention relates to a plant for generation of information indicative of the depth and the orientation of an object positioned below the surface of the ground which plant is adapted to use electromagnetic radiation emitted from and received by an antenna system associated with the plant and which plant has a transmitter and a receiver for generation of the electromagnetic radiation in cooperation with the antenna system mentioned and for reception of an electromagnetic radiation reflected from the object in cooperation with the antenna system, respectively. Various technical solutions and embodiments of such ground radar plants and various embodiments of methods for generation of information about the depth and position of the object in question from a detection by means of ground radars are known. Examples of such technical solutions are described in the following publications: U.S. Pat. Nos. 5,339,080, 5,192,952, 5,499,029, 4,504,033, 5,325,095, 4,430,653, 4,698,634, 4,062,010, 4,839,654 and 5,130,711. These U.S. patents are referred to and they are hereby incorporated in the present specification by reference. Especially U.S. Pat. No. 4,728,897 describes a technique which is relevant in the present context as this US patent discloses an antenna construction in *J which a number of dipoles are positioned symmectically around a common centre and are brought to pivot either mechanically or electrically for generation of and reception of electromagnetic radiation. This technology enables to a large extent achievement of relevant information about the position and orientation of the object in question, but the technique is still open to improvements and modifications rendering it possible to obtain an even substantially improved generation of information and thus a safer and more reliable identification of the depth and orientation of the object to be identified.
It is an object of the present invention to provide an ground radar plant, i.e. a plant of the type described in the introduction, which plant provides an improved functionality regarding identification of the object in question, compared to technical solutions of the prior art, and consequently provides an improved measuring technique, compared to technical solutions of the prior art.
This object together with numerous other objects, advantages and special features of the present invention which will be evident from the following detailed description is obtained by means of a plant of the type mentioned in the introduction, which plant is characterized by being adapted to use electromagnetic radiation emitted from and received by an antenna system associated with the plant and having a transmitter and a receiver for generation of the electromagnetic radiation in cooperation with the antenna system mentioned, and for reception of an electromagnetic radiation reflected from the object in cooperation with the antenna system, respectively, characterized in that the antenna system comprises a plurality of individual dipole antennas, which are positioned in relation to the geometrical centres of the antenna system with the centres of the various dipole antennas displaced in relation to the geometrical centre of the antenna system and that the plant has means for rotation, either mechanically or electrically, of the antenna system around or in relation to the geometric centre of the antenna system. The embodiment of the antenna system characteristic of the present invention with the various dipole antenna displaced in relation to the geometric centre of the antenna system enables a substantially more complex radiation of electromagnetic radiation and at the same time a more precise and subtle reception of electromagnetic radiation which makes the obtaining of a substantial improvement of the measuring technique possible.
The antenna system characteristic of the present invention may in accordance with two alternative embodiments be produced in a manner so that the individual dipole antenna are positioned radially from the geometric centre of the antenna system, still with the centres of the various dipole antenna positioned displaced in relation to the geometric centre of the antenna system and especially with the centres of the various dipole antennas positioned on a circle or on several circles with different radii and with the geometric centre of the antenna system coincident with the centres of the circles in question, or the various dipole antenna may alternatively form a triangle structure positioned symmetrically around the geometric centre of the antenna system, i.e. with dipoles positioned in a triangle and with the vertex of a triangle positioned in the geometric centre of the antenna system or with composite triangle structures forming a configuration positioned symmetrically around the geometric centre of the antenna system. Alternatively, these two dipole antenna embodiments may be combined, similarly provision of another radiation pattern, other geometric configurations than triangle structures may also be used, e.g. quadrangle or polygonal structures or combinations of several different multiangle structures.
The individual antenna elements of the antenna system of the plant according to the present invention, being characteristic of the present invention, forming parallel orientered sets of transmitter and receiver, or alternatively the individual antenna elements forming orthogonally oriented transmitter and receiver pairs. Furthermore, the individual antenna elements of the antenna system may be co-polar or alternatively cross-polar. These special features enable the use of a broad variety of embodiments.
The plant according to the present invention may comprise means for production of rotation of the antenna system and thus produce a rotation, either mechanically or electrically of the antenna system. Preferably, in the present invention electronic rotation is applied in order to obtain a thorough control of the roation and a substantial reduction of the total weight of the plant. The electronic rotation may be produced by shifting between the individual antenna elements of the antenna system and thus providing polarization of the electromagnetic field around the geometric centre in angular increments which typically may be in the order of 22.5°, 30°, 36° or divisions or multiples of such angles.
The antenna system of the plant according to the present invention may in accordance with one embodiment generate electromagnetic radiation and receive electromagnetic radiation at several individual frequences, preferably in the range of 100 MHz to 1 GHz in steps of 5 MHZ. The obtained advantage is the provision of a broad spectrum of reflections.
The plant according to the invention may comprise signal processing means for measurement of a transferring function, e.g. a voltage transfer function, current transfer function or combinations thereof or power transfer functions between signals between the radiation emitted by the antenna system and the radiation received by the antenna system. In the present invention a voltage transfer function for connected values of the angular change of the antenna system and the frequency of the signal emitted by the antenna system and the signal received by the antenna system is preferably measured.
The signal processing means of the plant according to the present invention may perform the transformation from frequency to time by Fourier transformation or by application of a mathematic exponential model with corresponding rational transfer function on the transfer function associated with a specific angle, for generation of a continuous-in-time function for each angle which is calculated at a predetermined number of discrete times with identical calculation moments for each angle. Furthermore, the signal processing means may perform a transformation from frequency to time by Fourier transformation or by use of a mathematic exponential mo
Gregersen Ole
Jensen Ole Kiel
Gregory Bernarr E.
Klein O'Neill & Singh, LLP
Malaa Geoscience Forvaltning AB
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