Communications: directive radio wave systems and devices (e.g. – Transmission through media other than air or free space
Patent
1998-02-18
1999-12-14
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Transmission through media other than air or free space
342 27, 342126, G01S 1332
Patent
active
060023570
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and a system of determining the location of an object in a medium having a permittivity substantially different to that of the permittivity of the object. More particularly, the present invention is concerned with a system for determining the depth of an object in the medium and/or a position on the surface of the medium closest to the object.
The location of objects, particularly metallic objects, in a medium such as the ground, using electromagnetic radiation, is a problem which has received much attention. Objects which lie within a medium and which have a permittivity which is different from that of the surrounding medium such that it will reflect the electromagnetic radiation. Typically the problem has been approached in the prior art by using pulsed radar systems in order to measure the propagation delay of the pulses travelling through the medium. Such systems are described in U.S. Pat. No. 3,775,765 and U.S. Pat. No. 3,806,795.
This technique however suffers from the disadvantage that in order to measure the depth of an object in the medium it is necessary to have some knowledge of the dielectric properties of the medium.
The problem of requiring knowledge of the dielectric properties of a medium has been avoided in U.S. Pat. No. 3,392,384 which discloses a technique for detecting the presence of an object in a medium. In this technique a pair of transmitting and receiving antennas are used to transmit electromagnetic radiation into the medium and receive electromagnetic radiation reflected from the object as well as undesired radiation reflected from the surface of the medium. In this technique the surface reflection is removed by comparing two channels. Although this arrangement does not require knowledge of the dielectric properties of a medium, it is unable to determine the depth of an object. The arrangement merely provides an indication of the presence of an object.
The object of the present invention is thus to provide a simple system for and a method of determining the position of an object in a medium without requiring knowledge of the dielectric properties of the medium or of the object.
SUMMARY OF THE INVENTION
The present invention provides a system for determining the depth of an object having a first permittivity in a medium having a second permittivity substantially different to the permittivity of said object; the system comprising transmitter means for transmitting electromagnetic radiation into said medium for reflection from said object; and receiver means for receiving radiation reflected from said object; said transmitter means being arranged in use to transmit electromagnetic radiation from either one or a plurality of transmission locations along an axis over a surface of said medium adjacent said object; and said receiver means being arranged in use to receive electromagnetic radiation either at one receiver location along said axis from said plurality of transmission locations after reflection from said object, or at a plurality of reception locations along said axis from either said one or said plurality of transmission locations after reflection from said object, the or each said transmission location and the or each reception location being separated by predetermined distances and arranged asymmetrically about a mid point of said axis; the system including measurement means to measure the time taken for electromagnetic radiation to propagate from the or each transmission location to the or each reception location by reflection from said object; and calculation means to calculate the depth of said object in said medium using the measured propagation times and the predetermined distances separating the or each transmission location and the or each reception location.
The present invention also provides a method of determining the depth of an object in a medium having a permittivity substantially different to the permittivity of the object, the method comprising the steps of transmitting electromagnet
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Pennock Stephen Raymond
Redfern Miles Alexander
London Electricity PLC
Sotomayor John B.
LandOfFree
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