WO2008039072A1 - A system for tracking objects - Google Patents

A system for tracking objects Download PDF

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Publication number
WO2008039072A1
WO2008039072A1 PCT/NO2006/000336 NO2006000336W WO2008039072A1 WO 2008039072 A1 WO2008039072 A1 WO 2008039072A1 NO 2006000336 W NO2006000336 W NO 2006000336W WO 2008039072 A1 WO2008039072 A1 WO 2008039072A1
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WO
WIPO (PCT)
Prior art keywords
mobile unit
transceiver
signal
tracking device
receiver
Prior art date
Application number
PCT/NO2006/000336
Other languages
French (fr)
Inventor
Arnt LØKE
Original Assignee
Tracking Systems As
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tracking Systems As filed Critical Tracking Systems As
Priority to PCT/NO2006/000336 priority Critical patent/WO2008039072A1/en
Publication of WO2008039072A1 publication Critical patent/WO2008039072A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/76—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein pulse-type signals are transmitted
    • G01S13/767—Responders; Transponders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
    • G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
    • G01S3/14—Systems for determining direction or deviation from predetermined direction
    • G01S3/28—Systems for determining direction or deviation from predetermined direction using amplitude comparison of signals derived simultaneously from receiving antennas or antenna systems having differently-oriented directivity characteristics
    • G01S3/32—Systems for determining direction or deviation from predetermined direction using amplitude comparison of signals derived simultaneously from receiving antennas or antenna systems having differently-oriented directivity characteristics derived from different combinations of signals from separate antennas, e.g. comparing sum with difference
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
    • G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
    • G01S3/14—Systems for determining direction or deviation from predetermined direction
    • G01S3/52—Systems for determining direction or deviation from predetermined direction using a receiving antenna moving, or appearing to move, in a cyclic path to produce a Doppler variation of frequency of the received signal
    • G01S3/54—Systems for determining direction or deviation from predetermined direction using a receiving antenna moving, or appearing to move, in a cyclic path to produce a Doppler variation of frequency of the received signal the apparent movement of the antenna being produced by coupling the receiver cyclically and sequentially to each of several fixed spaced antennas

Definitions

  • the present invention relates to a system and method for tracking objects with means operating on radio frequency waves.
  • AU systems include a small mobile unit that is to be carried by the object, and tracking equipment for tracing the position of the mobile unit.
  • ETS Electronic Tracking Systems markets a system using a combined GSM-UHF approach.
  • a mobile unit including a GSM device and a UHF transmitter is fastened to the object.
  • a coarse indication of the position of the object maybe obtained from the GSM network.
  • the UHF transmitter is activated via the GSM network.
  • a mobile direction-finder system is then used to locate the object.
  • Followit Tracking Service is a similar system relying on small mobile units, each including a GSM device and a GPS receiver.
  • the position of an object carrying the mobile unit is obtained from the GPS receiver and communicated to a central unit via the GSM network.
  • Such systems have a number of weak points primarily connected with the GSM system.
  • the coverage of a GSM system is very uneven, with frequent "shadow zones” and “white spots” in the outskirts with no coverage at all.
  • GSM systems are easily jammed.
  • Jamming transmitters are in fact commercially available for use in churches, restaurants, libraries, etc., where it is improper to receive telephone calls.
  • the rogue community has discovered that such jammers are handy for blocking the signals from tracking units, and jammers are now a standard item in the toolkit of a modern thief or robber.
  • the jammer will prevent the base station from discovering the existence of the GSM device in its cell, and the unit will thus effectively disappear from sight.
  • a GPS receiver will easily loose track of the satellite when carried inside a building, or concealed in a metal container.
  • Another object is to provide a system in which an object may be tracked from a large distance.
  • Fig. 1 is a schematic diagram showing the main components in a mobile unit used in the inventive system
  • Fig. 2 shows the corresponding direction-finder equipment used for tracking the mobile unit in fig. 1,
  • Fig. 3 illustrates how the direction-finder equipment is operated in large distance mode.
  • the system consists of a mobile unit 1 intended to be carried by the object in question, Fig. 1. It may e.g. be concealed inside a car, or placed in a suitcase for valuables. Even though a car body will have a screening action on the signals sent to and from the mobile unit, sufficient energy will slip trough to let the unit be tracked.
  • the unit 1 includes a transmitter 2 and a receiver 3 operating in the VHF band. The transmitter and receiver are connected to an antenna 4. The operation of the transmitter and receiver is controlled by a control unit 5. Normally the mobile unit is in an idle state waiting for an activation signal. When an activation signal is received, the transmitter 2 is brought into operation sending an identification signal.
  • the corresponding tracking device 21 is illustrated in fig. 2.
  • the tracking device 21 may be installed in a vehicle, e.g. a car or aeroplane, or may be a small portable device to be carried by personnel.
  • the device includes a transceiver 24, a Doppler receiver 22, a GPS receiver 23, an antenna switch 25 and four antennas 26a-d.
  • the tracking device 21 is connected to a computer system (not shown) via a computer interface 27.
  • the computer system may be an external personal computer or an internal dedicated processor system.
  • the computer system is adapted to control the operation of the tracking device, and may include a database over mobile units and their identification codes.
  • the transceiver 24 When it is desired to track the position of a mobile unit 1 , let's say if a car with mobile unit installed is reported as being stolen, the transceiver 24 will be operated by the control unit 28 to transmit an activation signal to the mobile unit 1.
  • the transceiver may transmit with high effect in order to secure activation of the mobile unit even in the presence of jamming transmitters.
  • the mobile unit 1 responds by transmitting a signal, either continuously or intermittently.
  • the primary tracking system is based on the Doppler receiver 22, which is connected to a number of antennas 26a-d, four in the figure.
  • the two, four or more antennas are arranged in a regular pattern.
  • the Doppler receiver 22 is connected to the antennas via antenna switch 25.
  • Said antenna switch 25 may alternatively connect the antennas to transceiver 24.
  • Doppler direction-finder systems are well known in the art, and will not be described in further detail here.
  • Doppler systems are based on frequency modulated signals with a bandwidth of 12.5 to 25 kHz. Under noise free conditions, signals down to about -130 dBm may be detected and tracked.
  • a Doppler system is efficient for finding the direction to a target source with great accuracy.
  • such systems are dependent on signals with relatively large signal strength. It was observed during tracking with the Doppler system, that the signal from the mobile unit could be heard at a large distance before the Doppler system became operable.
  • the tracking device was therefore supplemented with a large distance tracking system, which is illustrated in Fig. 3.
  • the transceiver will be connected to the four antennas in pairs.
  • antennas 26a and 26b are connected to the transceiver, with a resultant kidney- like antenna diagram 29.
  • the antenna switch 25 will switch the antennas in and out of circuit, effectively making the antenna scan four different directions in succession. The number of directions may be expanded using the diagonals, or by introducing phase shift elements.
  • the system will initially give a very coarse indication of the direction to the emitter source. When an emitter source is detected, the operator will stop the scanning and aim the antenna (or the vehicle) towards the target such that the received signal falls in the null in the antenna diagram 29. When the proper direction has been determined, the antenna diagram is reversed. The operator may then proceed towards the target, and eventually the Doppler system will take over as the primary direction indicator.
  • the system may employ two or more antennas; the resolution in direction improving with an increasing number of antenna pairs, but also with a corresponding increase in hardware costs.
  • the inventive tracking system may operate in any commercially available frequency VHF/UHF band, e.g. in the 170-174 MHz band.
  • This band is segmented in a number of channels, each 12.5 kHz wide.
  • the carrier from the mobile unit I is placed near the centre of one channel.
  • the carrier may drift a little, and the transceiver is therefore adapted to continuously scan the channel for signals.
  • the transceiver is using a narrow filter bandwidth, typical of 3 to 0.25 kHz width, with an additional DSP filter for discovering signals buried in noise.
  • the output from the receiver in the transceiver
  • the signals from the mobile unit are demodulated in the transceiver with a product detector for increased sensitivity.
  • the DSP filter is using a very narrow bandwidth of e.g. 1 to 5 Hz.
  • the signal from the mobile unit may appear as a weak signal in a mass of other, strong signals.
  • the transceiver is adapted to send a signal requesting the mobile unit to switch into a mode where it is sending a carrier with a very slowly varying frequency modulation. This low modulation frequency is needed to admit the signal through the narrow filter. Even though this also means a low information transfer rate, the signal may be easily identified and tracked.
  • the low information transfer rate in turns means that the identity of the source may not be detected (i.e. the identification code in the signal may not be detected) even if it is identified as a mobile unit belonging to the inventive system.
  • the signal amplitude strength will improve and the transceiver may be switched into a wider bandwidth allowing the information content in the signal to be read.
  • the sensitivity of the system is greatly increased. It is possible to hear and aim at signals down to -153 dBm. This is the audible limit; signals may in fact be observed visually to still lower levels. It is also possible to observe signals from the mobile unit 1 through the signals of jamming transmitters.

Abstract

A system for tracking an object, the object being equipped with a mobile unit (1), said mobile unit (1) including a transmitter (2) and a receiver (3), the system further including a tracking device (21) with a Doppler receiver (22) for short range direction finding, and in addition a narrow bandwidth transceiver (24) for long range direction finding, said transceiver (24) being adapted to send an activation signal to the mobile unit (1) and receive an identification signal from the mobile unit (1).

Description

A SYSTEM FOR TRACKING OBJECTS
Field of the invention
The present invention relates to a system and method for tracking objects with means operating on radio frequency waves.
Technical background
Today, there are available a number of systems for tracking objects. The objects in question may be money coffers or other containers for transporting valuable items, cash point equipment, trucks, cars, motorbikes, boats, post parcels, personal computers or even persons, pets and other animals. AU systems include a small mobile unit that is to be carried by the object, and tracking equipment for tracing the position of the mobile unit.
ETS (Electronic Tracking Systems) markets a system using a combined GSM-UHF approach. A mobile unit including a GSM device and a UHF transmitter is fastened to the object. A coarse indication of the position of the object maybe obtained from the GSM network. In order to obtain a more precise position, the UHF transmitter is activated via the GSM network. A mobile direction-finder system is then used to locate the object.
Followit Tracking Service is a similar system relying on small mobile units, each including a GSM device and a GPS receiver. The position of an object carrying the mobile unit is obtained from the GPS receiver and communicated to a central unit via the GSM network.
Such systems have a number of weak points primarily connected with the GSM system. The coverage of a GSM system is very uneven, with frequent "shadow zones" and "white spots" in the outskirts with no coverage at all. GSM systems are easily jammed. Jamming transmitters are in fact commercially available for use in churches, restaurants, libraries, etc., where it is improper to receive telephone calls. The rogue community has discovered that such jammers are handy for blocking the signals from tracking units, and jammers are now a standard item in the toolkit of a modern thief or robber. The jammer will prevent the base station from discovering the existence of the GSM device in its cell, and the unit will thus effectively disappear from sight. A GPS receiver will easily loose track of the satellite when carried inside a building, or concealed in a metal container.
Summary of the invention
It is an object of the present invention to provide a system for tracking objects that is practically immune against j ammers .
Another object is to provide a system in which an object may be tracked from a large distance.
The objects above are achieved in a system as covered in the appended patent claims.
Brief description of the drawings
The invention will now be described in detail in reference to the appended drawings, in which:
Fig. 1 is a schematic diagram showing the main components in a mobile unit used in the inventive system,
Fig. 2 shows the corresponding direction-finder equipment used for tracking the mobile unit in fig. 1,
Fig. 3 illustrates how the direction-finder equipment is operated in large distance mode.
Detailed description
The system consists of a mobile unit 1 intended to be carried by the object in question, Fig. 1. It may e.g. be concealed inside a car, or placed in a suitcase for valuables. Even though a car body will have a screening action on the signals sent to and from the mobile unit, sufficient energy will slip trough to let the unit be tracked. The unit 1 includes a transmitter 2 and a receiver 3 operating in the VHF band. The transmitter and receiver are connected to an antenna 4. The operation of the transmitter and receiver is controlled by a control unit 5. Normally the mobile unit is in an idle state waiting for an activation signal. When an activation signal is received, the transmitter 2 is brought into operation sending an identification signal. The corresponding tracking device 21 is illustrated in fig. 2. The tracking device 21 may be installed in a vehicle, e.g. a car or aeroplane, or may be a small portable device to be carried by personnel. The device includes a transceiver 24, a Doppler receiver 22, a GPS receiver 23, an antenna switch 25 and four antennas 26a-d. The tracking device 21 is connected to a computer system (not shown) via a computer interface 27. The computer system may be an external personal computer or an internal dedicated processor system. The computer system is adapted to control the operation of the tracking device, and may include a database over mobile units and their identification codes.
When it is desired to track the position of a mobile unit 1 , let's say if a car with mobile unit installed is reported as being stolen, the transceiver 24 will be operated by the control unit 28 to transmit an activation signal to the mobile unit 1. The transceiver may transmit with high effect in order to secure activation of the mobile unit even in the presence of jamming transmitters. The mobile unit 1 responds by transmitting a signal, either continuously or intermittently.
The primary tracking system is based on the Doppler receiver 22, which is connected to a number of antennas 26a-d, four in the figure. The two, four or more antennas are arranged in a regular pattern. The Doppler receiver 22 is connected to the antennas via antenna switch 25. Said antenna switch 25 may alternatively connect the antennas to transceiver 24. Doppler direction-finder systems are well known in the art, and will not be described in further detail here.
Doppler systems are based on frequency modulated signals with a bandwidth of 12.5 to 25 kHz. Under noise free conditions, signals down to about -130 dBm may be detected and tracked.
A Doppler system is efficient for finding the direction to a target source with great accuracy. However, such systems are dependent on signals with relatively large signal strength. It was observed during tracking with the Doppler system, that the signal from the mobile unit could be heard at a large distance before the Doppler system became operable. The tracking device was therefore supplemented with a large distance tracking system, which is illustrated in Fig. 3.
In this system, the transceiver will be connected to the four antennas in pairs. In the figure, antennas 26a and 26b are connected to the transceiver, with a resultant kidney- like antenna diagram 29. The antenna switch 25 will switch the antennas in and out of circuit, effectively making the antenna scan four different directions in succession. The number of directions may be expanded using the diagonals, or by introducing phase shift elements. Thus, the system will initially give a very coarse indication of the direction to the emitter source. When an emitter source is detected, the operator will stop the scanning and aim the antenna (or the vehicle) towards the target such that the received signal falls in the null in the antenna diagram 29. When the proper direction has been determined, the antenna diagram is reversed. The operator may then proceed towards the target, and eventually the Doppler system will take over as the primary direction indicator. The system may employ two or more antennas; the resolution in direction improving with an increasing number of antenna pairs, but also with a corresponding increase in hardware costs.
The inventive tracking system may operate in any commercially available frequency VHF/UHF band, e.g. in the 170-174 MHz band. This band is segmented in a number of channels, each 12.5 kHz wide. The carrier from the mobile unit I is placed near the centre of one channel. The carrier may drift a little, and the transceiver is therefore adapted to continuously scan the channel for signals. The transceiver is using a narrow filter bandwidth, typical of 3 to 0.25 kHz width, with an additional DSP filter for discovering signals buried in noise. The output from the receiver (in the transceiver) may be observed audibly or processed in a sound spectrum analysis program and displayed on a computer screen.
The signals from the mobile unit are demodulated in the transceiver with a product detector for increased sensitivity. To further increase the sensitivity, the DSP filter is using a very narrow bandwidth of e.g. 1 to 5 Hz. However, the signal from the mobile unit may appear as a weak signal in a mass of other, strong signals. To properly identify the signal from the mobile unit, the transceiver is adapted to send a signal requesting the mobile unit to switch into a mode where it is sending a carrier with a very slowly varying frequency modulation. This low modulation frequency is needed to admit the signal through the narrow filter. Even though this also means a low information transfer rate, the signal may be easily identified and tracked. The low information transfer rate in turns means that the identity of the source may not be detected (i.e. the identification code in the signal may not be detected) even if it is identified as a mobile unit belonging to the inventive system. When approaching the target, the signal amplitude strength will improve and the transceiver may be switched into a wider bandwidth allowing the information content in the signal to be read. By operating the system as a narrow bandwidth system, the sensitivity of the system is greatly increased. It is possible to hear and aim at signals down to -153 dBm. This is the audible limit; signals may in fact be observed visually to still lower levels. It is also possible to observe signals from the mobile unit 1 through the signals of jamming transmitters.

Claims

Claims
1. A system for tracking an object, the object being equipped with a mobile unit (1), said mobile unit (1) including a transmitter (2) and a receiver (3), characterized in that the system further includes a tracking device (21) with a Doppler receiver (22) for short range direction finding, and in addition a narrow bandwidth transceiver (24) for long range direction finding, said transceiver (24) being adapted to send an activation signal to the mobile unit (1) and receive an identification signal from the mobile unit (1).
2. A mobile unit (1) for use in an object tracking system, said unit (1) including a receiver (3), characterized in that the unit further includes a transmitter (2), said transmitter (2) being arranged to be activated by a signal received by said receiver (3) and to send a carrier modulated with an identification code.
3. A mobile unit as claimed in claim 2, said unit being arranged to send a carrier modulated with a slowly wobbling frequency modulation when ordered to.
4. A tracking device (21) for tracking an object, the object being equipped with a mobile unit (1), said mobile unit (1) including a transmitter (2) and a receiver (3), characterized in that the tracking device (21) includes a Doppler receiver (22) for short range direction finding, and in addition a narrow bandwidth transceiver (24) for long range direction finding, said transceiver (24) being adapted to send an activation signal to the mobile unit (1) and receive an identification signal from the mobile unit (1).
5. A tracking device as claimed in claim 4, wherein the transceiver (24) is adapted to be sequentially switched between a number of antennas (26a-d) arranged in a regular pattern.
6. A tracking device as claimed in claim 5, wherein the transceiver (24) is adapted to be sequentially switched between pairs of antennas (26a-d), whereupon a kidney- shaped direction diagram is achieved.
7. A tracking device as claimed in claim 4, wherein the transceiver (24) includes a product detector, and is adapted to receive signal from the mobile unit using said product detector.
8. A tracking device as claimed in claim 4, wherein the transceiver (24) includes a filter of 3 to 0.25 kHz bandwidth, and is receiving the signal from the mobile unit through said filter.
9. A tracking device as claimed in claim 4, wherein the transceiver (24) includes a DSP filter of 1 to 5 Hz bandwidth, and is receiving the signal from the mobile unit through said DSP Filter.
PCT/NO2006/000336 2006-09-29 2006-09-29 A system for tracking objects WO2008039072A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/NO2006/000336 WO2008039072A1 (en) 2006-09-29 2006-09-29 A system for tracking objects

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/NO2006/000336 WO2008039072A1 (en) 2006-09-29 2006-09-29 A system for tracking objects

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013167914A1 (en) * 2012-05-11 2013-11-14 Jacktrak Limited A communication device
CN104859589A (en) * 2015-04-28 2015-08-26 上海移为通信技术股份有限公司 Vehicle tracking system and method based on Doppler shift

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4596988A (en) * 1983-06-10 1986-06-24 Wanka James T Remote controlled tracking transmitter and tracking support system
US4818998A (en) * 1986-03-31 1989-04-04 Lo-Jack Corporation Method of and system and apparatus for locating and/or tracking stolen or missing vehicles and the like
US20020123353A1 (en) * 2001-02-02 2002-09-05 Paul-Andre Savoie Tracking system and method employing cellular network control channels
WO2002073562A1 (en) * 2001-03-12 2002-09-19 Eureka Technologies Partners, Llc Article locator system
WO2002095441A1 (en) * 2001-05-23 2002-11-28 Le Guen, Jeanne Equipment for assistance in locating a mobile object such as a stray or missing animal

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4596988A (en) * 1983-06-10 1986-06-24 Wanka James T Remote controlled tracking transmitter and tracking support system
US4818998A (en) * 1986-03-31 1989-04-04 Lo-Jack Corporation Method of and system and apparatus for locating and/or tracking stolen or missing vehicles and the like
US20020123353A1 (en) * 2001-02-02 2002-09-05 Paul-Andre Savoie Tracking system and method employing cellular network control channels
WO2002073562A1 (en) * 2001-03-12 2002-09-19 Eureka Technologies Partners, Llc Article locator system
WO2002095441A1 (en) * 2001-05-23 2002-11-28 Le Guen, Jeanne Equipment for assistance in locating a mobile object such as a stray or missing animal

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013167914A1 (en) * 2012-05-11 2013-11-14 Jacktrak Limited A communication device
US20150126216A1 (en) * 2012-05-11 2015-05-07 Jacktrak Limited Communication device
CN104662434A (en) * 2012-05-11 2015-05-27 杰克创克有限公司 A communication device
CN104859589A (en) * 2015-04-28 2015-08-26 上海移为通信技术股份有限公司 Vehicle tracking system and method based on Doppler shift
CN104859589B (en) * 2015-04-28 2017-05-31 上海移为通信技术股份有限公司 Vehicle tracing system and method based on Doppler frequency shift

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