Communications: directive radio wave systems and devices (e.g. – Determining distance – Material level within container
Patent
1994-11-22
1998-03-31
Lobo, Ian J.
Communications: directive radio wave systems and devices (e.g.,
Determining distance
Material level within container
342120, 342123, 367908, 73290V, 73290R, G01S 1302
Patent
active
057343462
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of and apparatus for detecting the displacement of a target in a given environment, and also to a method of and apparatus for determining the level of a sample in a container, especially, but not exclusively, by radar techniques.
The invention relates particularly to liquid level sensing in a tank, but is also applicable to altimetry and intruder detection. It is most suited to relatively short range applications.
2. Related Art
It is known, for example from a paper entitled "Geophysical Radar Designs", by Oswald, G. K. A. (IEEE Proceedings, Volume 1-35, Part F, No. 4, August 1988), to detect the displacement of a target relative to its environment by transmitting a radio-frequency impulsive signal towards the target, sensing the return signals from the target and the environment, and detecting displacement of the target by detecting any Doppler shift in the return signal waveform by simple high pass or band pass filtering.
In that such a technique relies on the Doppler effect, it can only function successfully when there is a significant relative motion between the target and the environment (as would be the case, for example, if an aircraft were the "target" and the terrain were the environment). Such a technique cannot function at all when there is no relative movement between the target and the environment, since in this case there will be no Doppler shift. Hence this technique is not suitable for sensing the level of a sample in a container, since, in many cases, the level might be expected to change only slowly, if at all. For example, for petrochemical or soap tanks, changes of perhaps only 2.5 cm per day in level are commonly experienced.
A radar-based technique for measuring the level of a liquid in a tank is also known. In this technique, a narrow-beam, high frequency (for example 10-12 GHz), narrow bandwidth (for example 3% of the centre frequency) frequency modulated transmit signal is transmitted via an antenna of roughly 0.3 m diameter towards a small region of the liquid surface. It will be appreciated that the frequency has to be relatively high and the antenna has to be relatively wide in order to produce a sufficiently narrow beam so that only this small region of the liquid surface is irradiated. The displacement of the surface is detected by sensing the return signals from solely the surface.
Such a technique suffers from the disadvantages firstly that it is expensive to implement because of the relatively high frequency of operation. Secondly, it is limited by the size of its antenna to use in relatively wide tanks. Thirdly, it cannot take any account of the environment (in this case, the walls of the tank). This can lead to a loss of accuracy or effectiveness where the technique is used in a relatively small tank.
A further radar-based technique is disclosed in European Patent Application No. 88302996.9. A guided-wave level sensor based on wide-band technology is disclosed in United Kingdom Patent Application No. 8913720.2.
SUMMARY OF THE INVENTION
The present invention seeks to overcome the above problems, and especially to provide apparatus having resolution and performance similar to the prior art liquid level measuring apparatus, but at a significantly lower cost.
According to the present invention, there is provided a method of detecting the displacement of a target in a given environment, comprising: and the stored reference data; dependence on the displacement of the target.
By storing reference data comprising data representative of the environment and detecting the displacement of the target by comparing the return signals and the stored reference data, a displacement detection technique can be provided which can distinguish a target from its environment not only when their relative speed is high but even when there is no or very low relative motion. The comparison between the return signals and the reference data can serve to enhance the target return signal relative to the en
REFERENCES:
patent: 3775765 (1973-11-01), di Piazza et al.
patent: 4044353 (1977-08-01), Levy
patent: 4320659 (1982-03-01), Lynnworth et al.
patent: 4847623 (1989-07-01), Jean et al.
patent: 5181039 (1993-01-01), Oswald et al.
patent: 5233352 (1993-08-01), Cournane
Michiguchi et al, "Advanced Subsurface Radar System for Imaging Buried Pipes", IEEE Transactions on Geoscience and Remote sensing, vol. 26, Nov. 1988, New York, US, pp. 733-739.
Thurn, "Ultrasonic Detection Sensors for Sonar Bero Proximity Swiches", Siemens Energy & Automation, vol, 9, No. 2, Jul. 1989, Berlin DE, pp. 10-11.
Electronics, vol. 48, No. 17, 21 Aug. 1975, New York US, pp. 5E-6E "Microwave Radar Measures Precisely".
"Geophysical Radar Design" by G.K.A. Oswald, IEE Proceedings, vol. 135, Part F, No. 4, Aug. 1988.
"Introduction to Radar Systems" Second Edition 1981 by Skolnik, published by McGraw-Hill, pp. 420-434.
U.S. application Ser. No. 07/878,754, Oswald et al.
Oswald Gordon Kenneth Andrew
Richardson Alan Trevor
Cambridge Consultants Limited
Lobo Ian J.
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