Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-05-11
2001-12-25
Trieu, Van T. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S553000, C340S554000
Reexamination Certificate
active
06333691
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a motion detector or proximity switch for detecting moving objects, wherein a high-frequency electromagnetic radiation is produced via a freely oscillating oscillator and is emitted via a transmitting antenna, and the radiation reflected from the moving object and modified due to the Doppler effect is detected with regard to change in its phase angle or amplitude via a receiving antenna and is compared in an evaluation device with the parameters of the emitted radiation for the production of an output signal,.
2. Background Art
Motion detectors of the type in question are used, for example, for spatial monitoring. They serve accordingly as a type of proximity switch. They are used, for example, as automatic door openers, which detect the approach of a person and generate a signal triggering a control signal to the door opening device.
Motion detectors are also known which automatically switch on the lighting in the exterior region of houses and internal spaces as people approach.
In other applications it is proposed to use motion detectors for spatial monitoring in conjunction with alarm systems.
Many known motion detectors work on the basis of light barriers or by detecting infrared radiation emitted by people.
Both methods have the disadvantage, particularly for use as alarm systems, that they can be easily recognized due to the required construction size and can accordingly therefore also be manipulated. Furthermore, the known methods have the inherent disadvantage that they are sensitive to light and temperature, making them prone to faults and only usable under certain conditions.
Motion detectors are also already known which work by using the Doppler effect. DE 39 22 165 A1 describes, for example, a Doppler radar sensor which is arranged as a planar circuit on a substrate with an antenna on the top of the substrate and an evaluation unit connected after the sensor. The sensor emits continuous or pulsed signals in the microwave range (3 to 30 gigahertz) via an antenna. These signals are reflected by objects moved in the radiation field and, displaced by the Doppler frequency, picked up again by the antenna and detected by the evaluation unit.
Up until now motion detectors of the type described were used as separate apparatus on doors, walls or ceilings due to their mode of construction. For this reason they are often exposed to manipulation, deliberate damage or even destruction. Moreover, conventional motion detectors of the type in question have a very high power requirement, being dependent on a continuous power supply, an emergency power supply, if available, being only temporarily available, e.g. from a battery or an accumulator.
SUMMARY OF THE INVENTION
Following on from this, the object of the invention is to design a motion detector of this type so that it has a flat and compact construction and accordingly can be arranged in such a way that it is protected from manipulation, deliberate damage or destruction.
According to the invention this object is achieved in a motion detector comprising a freely oscillating oscillator of which the feedback is guaranteed via at least one transmitting antenna ANT RX and at least one receiving antenna ANT TX, which are orientated in the direction of the object and are coupled via lateral radiation or radiation leakage.
The circuit according to the invention is distinctive in that it reacts particularly sensitively even in the case of relatively low object speeds, compared to the conventional Doppler radar principle. It can be constructed very compactly and has an extremely low energy requirement, so new fields of application are possible in which operation is by battery or accumulator or energy sources such as solar cells.
Interference by the material surrounding the motion sensor is prevented by an advantageously selected frequency in the microwave range. The radiation of this wavelength penetrates materials such as glass, ceramics, plastics, masonry, wood and perforated metal without significant loss, so a motion detector of this type can also be hidden behind these materials or can be arranged in a casing made from these materials, optionally designed unobtrusively.
A motion detector of the type in question is accordingly suited as an alarm to prevent unauthorized removal of suitcases, handbags, beach bags and bicycles and for securing electrical and electronic devices. An alarm signal can be triggered, for example, by the approach of an unauthorized person, while this alarm is suppressed in the case of an authorized person equipped with an electronic signal transmitter. If this authorized person leaves the detection range of the sensor protecting the electronic device, the accessibility of data and information is automatically suppressed.
An advantageous embodiment of the invention is described in more detail hereinafter with reference to the drawings.
REFERENCES:
patent: 3673590 (1972-06-01), Corvi et al.
patent: 3716854 (1973-02-01), Charlot
patent: 3801977 (1974-04-01), Cotter
patent: 3838424 (1974-09-01), Goldfischer
patent: 4027303 (1977-05-01), Neuwirth et al.
patent: 4107684 (1978-08-01), Watson, Jr.
patent: 4791420 (1988-12-01), Baba
patent: 39 22 165 (1991-01-01), None
Browdy and Neimark
Trieu Van T.
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