WO1997031275A1 - Method and device for detecting an object in a region to be monitored - Google Patents
Method and device for detecting an object in a region to be monitored Download PDFInfo
- Publication number
- WO1997031275A1 WO1997031275A1 PCT/DE1997/000299 DE9700299W WO9731275A1 WO 1997031275 A1 WO1997031275 A1 WO 1997031275A1 DE 9700299 W DE9700299 W DE 9700299W WO 9731275 A1 WO9731275 A1 WO 9731275A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- threshold value
- area
- signal
- alarm signal
- generated
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/22—Electrical actuation
- G08B13/24—Electrical actuation by interference with electromagnetic field distribution
- G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/12—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with electromagnetic waves
Definitions
- the invention relates to a method according to the preamble of claim 1 and a corresponding arrangement according to the preamble of claim 4.
- a transmitter sends a high-frequency interrogation signal from one side of the area through it to an opposite side, where a transponder consisting of an antenna and a surface wave delay element connected to it with the interposition of an interdigital transducer.
- the received interrogation signal converted into a surface is reflected in the surface wave delay element and, after being converted back into an electrical signal, is sent back from the antenna in the direction of the side of the area having the transmitter, where it is detected by a receiver and fed to an evaluation device. If there is an object in the area to be monitored, the emitted signal is attenuated.
- a problem common to the known methods or arrangements is the optimal setting of the threshold value, on the one hand to enable reliable detection of objects in the area to be monitored and on the other hand to avoid incorrect detections due to detection sensitivity being too high.
- the solution according to the invention is based on the knowledge that the amplitude of the received modified interrogation signal can change due to temperature, weather or other environmental influences, without an object to be detected being in the area to be monitored. Naturally, these changes take place very slowly, but considerable deviations can occur in the long run.
- the mean value of the received modified query signal formed according to the invention follows the slow changes of this signal. Accordingly, the threshold value generated from the mean value also follows these slow signal changes with the spacing of the specified safety margins. Rapid signal changes caused by objects penetrating into the area to be monitored, on the other hand, have a delayed effect in the mean value and thus Threshold value off so that the rapidly changing modified query signal violates the threshold value and thus triggers an alarm.
- the threshold value present at the beginning of the alarm state is advantageously frozen until the end of the alarm state.
- a slowly building up obstacle such as e.g. If, for example, a snow drift can be detected, an alarm is additionally triggered if the mean value or the threshold value generated therefrom violates a limit value in the form of a further threshold value.
- Figure 1 is a schematic diagram of an embodiment of the arrangement according to the invention.
- FIG. 2 shows a block diagram of the circuit part from FIG. 1 relating to threshold value tracking.
- FIG. 1 shows a schematic representation of an area 1 to be monitored for the presence of objects, on the side 2 of which a transmitter 3 is arranged.
- the transmitter 3 contains a transmission oscillator 4, which generates an output signal with a transmission frequency fi of 2.5 GHz, for example.
- a frequency modulator 5 controlling this is connected to the transmission oscillator 4, which modulates the transmission frequency fi with a
- Modulation frequency of 1 kHz, for example, and a frequency swing of z. B. +/- 6 MHz frequency modulated.
- the frequency-modulated output signal of the transmission oscillator 4 is fed to an amplifier 6 and then emitted as an interrogation signal via an antenna 7 into the area 1 to be monitored.
- the received interrogation signal is processed in a downstream band filter and amplifier stage 11 and then fed to a signal modulator 12 in which the received interrogation signal is mixed with the output signal of an oscillator 13.
- the oscillator frequency f 2 is in a frequency range from 4 to 7 MHz, for example.
- the thus modified interrogation signal with the frequency fi +/- f 2 is then fed via an amplifier 14 to an antenna 15 and is radiated back by the latter through the area 1 to be monitored on its side 2.
- a receiver 16 is arranged there, in which the returned, modified query signal is received by means of an antenna 17 and is fed via an amplifier 18 to a further signal mixer 19, which also receives the output signal of the transmission oscillator 4.
- F- by mixing the two signals with the frequencies f 2 and f +/-: generates Si ⁇ gnalmischer 19 output a signal f is the frequency of the oscillator 13 of the transponder 2 comprises. 9
- This signal is fed to an evaluation device 20 with a threshold value detector contained therein and monitored for falling below a predetermined threshold value.
- the interrogation signal is attenuated with a certain degree of damping when passing through area 1. If, on the other hand, there are any objects in area 1, the attenuation of the interrogation signal is greater and the modified interrogation signal received is therefore weaker.
- the threshold value in the evaluation device 20 is therefore to be set such that the output signal of the further signal mixer 19 is above the threshold value in the case of an object-free area 1 and, in the presence of objects, falls below the threshold value and thereby triggers the output of an alarm signal A.
- FIG. 2 shows a more detailed block diagram of the evaluation device 20.
- This contains a low-pass filter 21 with a cut-off frequency of approximately 100 Hz, in which the signal coming from the signal mixer 19 is freed of noise components.
- the noise-free signal U obtained in this way is then compared in a threshold value detector 22 with a threshold value U r ⁇ fi. If the signal U is below the threshold value U r ⁇ fi, the threshold value detector 22 emits an alarm signal Ai as long as this state persists.
- the threshold value U re fi is derived from the signal U by feeding it to a device 23 for averaging and the mean value M continuously formed there in a device 24 by a safety margin to the threshold value U ref: er is added.
- the safety margins can be linked to the mean M as an additive or multiplicative quantity.
- the device 23 for averaging contains an integrator 25 which has a comparatively large time constant of approximately 10 s.
- An integrator / digital converter 26, a digital storage device 27 and a digital / analog converter 28 are arranged in series after the integrator 25, the digital / analog converter 28 providing the mean value M on the output side.
- the memory device 27 is controlled by a clock generator 29 for the clockwise acceptance of the signal at the output of the analog / digital converter 26 with a clock frequency of 1 Hz, for example.
- the integration of the signal U and the subsequent intermittent adoption of the integration result ensures that rapid changes in the signal U are not detected and stored.
- the mean value M and thus the threshold value U r ⁇ f ⁇ thus only follows slow changes in the signal U and thus adapts to the external conditions of the area 1 to be monitored (FIG. 1).
- the mean value M but it can also be the threshold value U r e f i, in a further threshold value detector 30 with a further threshold value U re . 2 compared, which can be set depending on the circumstances and represents a minimum value below which the threshold value U re . ⁇ may never decrease.
- a drop in the threshold value U r efi below this value leads to the generation of a further alarm signal A 2 .
- the two alarm signals Ai and A 2 are combined via an OR gate 31 to the alarm signal A.
- the threshold value U re ⁇ is no longer adapted to the average time profile of the signal U, in this case the digital average value M stored in the memory device 27 and thus the resultant The threshold value U ref ⁇ frozen in that the alarm signal A x blocks the clock control of the memory device 27 via a controllable switch 32.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Electromagnetism (AREA)
- Remote Sensing (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Geophysics (AREA)
- Automation & Control Theory (AREA)
- Computer Security & Cryptography (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP97914156A EP0883818A1 (en) | 1996-02-22 | 1997-02-17 | Method and device for detecting an object in a region to be monitored |
NO983249A NO983249L (en) | 1996-02-22 | 1998-07-14 | Method and apparatus for detecting an object in an area to be monitored |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19606675.1 | 1996-02-22 | ||
DE1996106675 DE19606675A1 (en) | 1996-02-22 | 1996-02-22 | Method and device for detecting an object in an area to be monitored |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1997031275A1 true WO1997031275A1 (en) | 1997-08-28 |
Family
ID=7786152
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/DE1997/000299 WO1997031275A1 (en) | 1996-02-22 | 1997-02-17 | Method and device for detecting an object in a region to be monitored |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0883818A1 (en) |
CA (1) | CA2246993A1 (en) |
DE (1) | DE19606675A1 (en) |
NO (1) | NO983249L (en) |
WO (1) | WO1997031275A1 (en) |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3995270A (en) * | 1975-06-16 | 1976-11-30 | The United States Of America As Represented By The Secretary Of The Navy | Constant false alarm rate (CFAR) circuitry for minimizing extraneous target sensitivity |
US4107678A (en) * | 1976-09-28 | 1978-08-15 | Westinghouse Electric Corp. | Polarization correlation target seeker |
US4725841A (en) * | 1983-06-30 | 1988-02-16 | X-Cyte, Inc. | System for interrogating a passive transponder carrying phase-encoded information |
US5225669A (en) * | 1990-11-15 | 1993-07-06 | Telefunken Electronic Gmbh | Sensor system with adjustment for ambient conditions |
EP0660135A2 (en) * | 1993-12-23 | 1995-06-28 | Trw Inc. | Radar signal processor |
Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2806448C2 (en) * | 1978-02-15 | 1985-01-10 | Brown, Boveri & Cie Ag, 6800 Mannheim | System for property security and personal protection by means of a microwave barrier |
GB2110825B (en) * | 1981-11-06 | 1986-04-30 | Outokumpu Oy | Apparatus for detecting metal objects |
DE3232437C2 (en) * | 1982-09-01 | 1985-03-21 | Brown, Boveri & Cie Ag, 6800 Mannheim | Method for increasing the security of an access control system |
US4899158A (en) * | 1987-09-26 | 1990-02-06 | Matsushita Electric Works, Ltd. | Moving object discriminating system |
AU622114B2 (en) * | 1988-07-08 | 1992-04-02 | Zetetic International Limited | Method and apparatus for selectively detecting objects |
IT1265721B1 (en) * | 1992-11-11 | 1996-12-02 | Alessandro Manneschi | METAL DETECTOR WITH MULTIPOLAR WINDINGS WITH THE ELIMINATION OF NEUTRALIZING EFFECTS |
IT1260208B (en) * | 1992-11-19 | 1996-04-02 | Giovanni Manneschi | PERFECTED METAL DETECTOR |
DE4240921C1 (en) * | 1992-12-04 | 1994-05-11 | Alessandro Manneschi | Metal detector for locating hidden weapons - compares signals using reception windings at different heights, to correct non-linearity |
DE9305611U1 (en) * | 1993-04-08 | 1994-05-05 | Siemens Ag | Arrangement for detecting an obstacle |
DE4336799A1 (en) * | 1993-10-28 | 1995-05-04 | Sel Alcatel Ag | Device for the detection of, and reading out from, transponders which move relative to this device |
DE9411602U1 (en) * | 1994-07-18 | 1995-08-17 | Siemens Ag | Arrangement for the detection of objects in an area to be monitored |
-
1996
- 1996-02-22 DE DE1996106675 patent/DE19606675A1/en not_active Withdrawn
-
1997
- 1997-02-17 CA CA 2246993 patent/CA2246993A1/en not_active Abandoned
- 1997-02-17 WO PCT/DE1997/000299 patent/WO1997031275A1/en not_active Application Discontinuation
- 1997-02-17 EP EP97914156A patent/EP0883818A1/en not_active Withdrawn
-
1998
- 1998-07-14 NO NO983249A patent/NO983249L/en unknown
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3995270A (en) * | 1975-06-16 | 1976-11-30 | The United States Of America As Represented By The Secretary Of The Navy | Constant false alarm rate (CFAR) circuitry for minimizing extraneous target sensitivity |
US4107678A (en) * | 1976-09-28 | 1978-08-15 | Westinghouse Electric Corp. | Polarization correlation target seeker |
US4725841A (en) * | 1983-06-30 | 1988-02-16 | X-Cyte, Inc. | System for interrogating a passive transponder carrying phase-encoded information |
US5225669A (en) * | 1990-11-15 | 1993-07-06 | Telefunken Electronic Gmbh | Sensor system with adjustment for ambient conditions |
EP0660135A2 (en) * | 1993-12-23 | 1995-06-28 | Trw Inc. | Radar signal processor |
Also Published As
Publication number | Publication date |
---|---|
CA2246993A1 (en) | 1997-08-28 |
NO983249D0 (en) | 1998-07-14 |
NO983249L (en) | 1998-08-21 |
DE19606675A1 (en) | 1997-08-28 |
EP0883818A1 (en) | 1998-12-16 |
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