GB2243739A - Frequency modulation distance measurement of active target - Google Patents
Frequency modulation distance measurement of active target Download PDFInfo
- Publication number
- GB2243739A GB2243739A GB9009510A GB9009510A GB2243739A GB 2243739 A GB2243739 A GB 2243739A GB 9009510 A GB9009510 A GB 9009510A GB 9009510 A GB9009510 A GB 9009510A GB 2243739 A GB2243739 A GB 2243739A
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- GB
- United Kingdom
- Prior art keywords
- frequency
- signal
- measurement
- distance
- unit
- Prior art date
- Legal status (The legal status 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 status listed.)
- Withdrawn
Links
- 238000005259 measurement Methods 0.000 title claims abstract description 81
- 238000000034 method Methods 0.000 claims abstract description 13
- 230000001419 dependent effect Effects 0.000 claims abstract description 4
- 238000004891 communication Methods 0.000 claims description 11
- 230000005540 biological transmission Effects 0.000 description 11
- 101150066718 FMOD gene Proteins 0.000 description 4
- 230000001960 triggered effect Effects 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005670 electromagnetic radiation Effects 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
- G08B21/02—Alarms for ensuring the safety of persons
- G08B21/0202—Child monitoring systems using a transmitter-receiver system carried by the parent and the child
- G08B21/023—Power management, e.g. system sleep and wake up provisions
-
- 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
- G01S13/82—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted
-
- 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
- G01S13/82—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted
- G01S13/825—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted with exchange of information between interrogator and responder
-
- 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
- G01S13/82—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted
- G01S13/84—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted for distance determination by phase measurement
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
- G08B21/02—Alarms for ensuring the safety of persons
- G08B21/0202—Child monitoring systems using a transmitter-receiver system carried by the parent and the child
- G08B21/0286—Tampering or removal detection of the child unit from child or article
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
- G08B21/18—Status alarms
- G08B21/24—Reminder alarms, e.g. anti-loss alarms
Landscapes
- Engineering & Computer Science (AREA)
- Remote Sensing (AREA)
- Radar, Positioning & Navigation (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Computer Networks & Wireless Communication (AREA)
- Health & Medical Sciences (AREA)
- Child & Adolescent Psychology (AREA)
- General Health & Medical Sciences (AREA)
- Burglar Alarm Systems (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
A technique for short range distance measurement using sub-microwave radio frequency signals in which the distance between a measurement unit and a co-operative active target unit is determined as follows: The measurement unit transmits a carrier signal which is frequency modulated with a low frequency modulation signal. This is received by the target unit which applies a small frequency shift to the signal and re-transmits it. The measurement unit receives the frequency shifted signal and mixes it with its transmitted signal to form a further frequency modulated signal in which the carrier frequency is equal to the frequency shift applied by the target unit and the modulation signal is at the frequency of the transmitter modulation and takes a form dependent on the round trip delay between measurement and target units and hence distance. The nature of the dependence is determined by the modulation waveform. If this is sinusoidal, the modulation amplitude is directly proportional to distance. By measuring this amplitude the distance can thus be determined. As a result of the frequency shift in the target unit, forward and return paths can be separated and therefore operation at sub-microwave radio frequencies is possible. <IMAGE>
Description
(Technical Field)
This invention relates to a technique for short-range distance measurement using radio frequency signals.
(Back ground)
Distance measurement by measuring the time taken for electromagnetic radiation to travel from a measurement point to a target and back to the measurement point is well known. For significant distances, measurements can be made using pulsed transmissions and directly measuring the trip time. For smaller distances the Continuous Wave Frequency Modulated (CWFM) technique is commonly used. In this technique, a carrier is frequency modulated with a time varying modulation signal and transmitted towards a target. The signal reflected from the target is received and mixed with the transmitted signal to give an output which is dependent on the round trip delay and hence the distance between the measurement point and the target.This technique is used in the laser rangefinder for instance in which a laser beam is frequency modulated with a triangular signal to give an output whose frequency smoothly ramps between two values. The result of mixing the transmitted and received signals is then a constant frequency whose value is proportional to distance.
Existing CWFM systems require that the transmitted and received signals can be separated at the measurement point. This restricts their application to microwave frequencies and above where sufficient antenna gain can be realised to separate the forward and retum paths. Inherent in this situation is the need to align the antenna in the direction of the target.
(Technical Features)
The present invention relates to a CWFM distance measurement technique suitable for use with sub-microwave radio frequencies which allows measurement of the distance from a measurement unit to an active target unit, and in which there is no requirement to align the measurement unit in the direction of the target.
According to a preferred aspect of the present invention, a radio frequency transmitter forming part of the measurement unit is frequency modulated with a time varying modulation signal.
This signal is received by the target unit, which applies a small frequency shift to the signal and re-transmits it. The measurement unit receives the frequency shifted signal and mixes it with its transmitted signal to form a further frequency modulated signal in which the carrier frequency is equal to the frequency shift applied by the target unit and the modulation signal is at the frequency of the transmitter modulation and dependent on the round trip delay between measurement and target units and hence distance. As a result of the frequency shift in the target unit, forward and return paths can be separated and therefore operation at submicrowave radio frequencies is possible.
According to a particular aspect of the invention, the measurement unit transmitter is modulated with a sinusoidal signal so that when the signal from the target unit is received by the measurement unit and mixed with the measurement unit's transmitted signal, the resulting frequency modulated signal is also modulated by a sinusoid and has a modulation amplitude or peak frequency deviation which is directly related to distance.
According to a particular aspect of the invention, the measurement unit is normally not transmitting and transmits a burst of signal of duration sufficient for a distance measurement to be performed only at such times as it requires to know the distance of the target. The target unit only transmits when it is receiving a signal from the measurement unit allowing both units to realise a reduction in power consumption.
According to a particular aspect of the invention, the measurement unit transmits a burst of signal in accordance with a defined time schedule allowing the transmitter and receiver sections of one or both units to be switched off between bursts realising a reduction in power consumption.
According to a further aspect of the invention, the modulation signal is itself modulated by
Frequency Shift Keying (FSK) or otherwise to give a communication means from the measurement unit to the target unit. In a particular aspect of the invention, this communication is used to address specific targets allowing operation with a single measurement unit and multiple targets. In a further particular aspect both transmission in randomly spaced bursts and addressing using the communications link is used to prevent interference between co-located systems.
(Examples)
The preferred embodiments of the invention will now be described by way of example with reference to the accompanying diagrams of which:
Figure 1 shows a continuous operation distance measurement system using a sine wave modulation signal but with no communication channel between measurement unit and target;
Figure 2 shows a method of adding an FSK communication channel to the figure 1 system;
Figure 3 shows a suitable communication protocol to provide for multiple targets and colocated operation of systems;
Figure 4 shows how a distance triggered alarm may be constructed;
Figure 5 shows an application of the technique to the protection of belongings carried with the person;
Figure 6 shows an application of the technique as a child straying alarm;
Figure 7 shows an application of the technique in an electronic detention system;;
Figure 8 shows an application of the technique for the protection of unattended goods or equipment; and
Figure 9 shows an application of the technique for position location or tracking.
The modulation oscillator 1 produces a sine wave of frequency food. In a typical implementation this might be about lkHz. This is used to frequency modulate the main transmit oscillator 2 of frequency f0 to a peak deviation of Af giving a transmission signal fTx at the output of 2 of frequency: rH= fo + Af sin[27Tfmodt] (1)
This signal is amplified and fed to an aerial 3 from which it travels over the distance to be measured r to the target unit.
The target unit receives the signal from the measurement unit via an aerial 4, adds a frequency offset foffset by means of an oscillator 5 and single sideband mixer 6 and transmits the resultant signal back to the measurement unit via a separate aerial 7. The offset frequency must be large enough to prevent instability due to either unit picking up its own transmitted signal, but otherwise is not critical. For a transmission frequency f0 of a few hundred megahertz, fOrf,et might typically be 100kHz.
The returned signal is received by the measurement unit at 8, amplified and presented to a mixer 9. The frequency of the received signal at the mixer is given by: fRK fo + foffset + #f sin[2#sin[2#fmod(t - 2r / c - td)] (2) where c is the speed of light in the medium, the term 2r/c accounts for the round trip delay to and from the target unit and td is the sum of time delays in the target unit and various amplifier stages.
The mixer 9 produces a difference frequency signal at its output whose frequency fx is given by: = fTz fRH = foffset + 2#fsin[2#fmod(r / c + td / 2)]cos[2Kf,,,(t-rlc: 1d /2)] (3)
This corresponds to a carrier of frequency f0et which is frequency modulated by the sinusoidal modulation signal food. The modulation is subject to a negligibly small phase shift with respect to the oscillator 1 and has a peak deviation (FM modulation amplitude) of: At out = 2#f sin[2#fmod(r / c + td / c + td / 2)] (4) Since fmod(r I C + 1d / 2) < < 1, this simplifies to::
Afout = 4##ffmod(r / c + td /2) (5)
Thus, the degree of frequency modulation at the output of the receive mixer 9 is directly proportional to range r.
The output of the mixer may be presented to a limiter/discriminator 10 of gain KD V/Hz which will give a sinusoidal signal at its output at the modulation frequency whose amplitude is proportional to range. This signal can be detected by means of a synchronous demodulator 11 and low pass filter 12 to give a final DC output signal V0 which is proportional to range of: Uo = 2/#KD4##ffmod(r / c + td / 2) (6) This signal is available at the measurement unit and gives the distance to the target unit. The offset error term due to td can be compensated for by calibration if required.
Aerials 3 and 8 on the measurement unit may be combined as a single aerial and similarly aerials 4 and 7 on the target unit.
The system can be extended to provide a low data rate communication channel as shown in figure 2. The data input signal is made to Frequency Shift Key (FSK) modulate the modulation oscillator 1 within the measurement unit. From equation 6 it can be seen that changes to the modulation frequency affect the ranging output signal and therefore data would not normally be transmitted whilst ranging is taking place. Within the target unit, the modulation signal is recovered by means of a limiter/discriminator 13 and fed to a phase locked loop FSK demodulator 14 to extract the data signal. Using this technique, a data rate of typically a few hundred bits per second is achievable.
The provision of communication between measurement unit and target unit allows operation with multiple targets where a single measurement unit can measure the distance to a number of specified targets. It also allows co-located operation of a number of measurement/target unit sets and the incorporation of power consumption reduction measures which are suitable for colocated operation.
Each measurement unit generates pseudo-randomly spaced transmission bursts according to a sequence which is based on the measurement unit serial number or some other source of uniqueness. This ensures that repeated transmit collisions between co-located measurement units cannot occur. Each transmission burst consists of a synchronisation section 15, the address 16 of a target unit which must be unique amongst all target units and hence again is likely to be based on a serial number, a time code 17 which indicates how long the target unit may power-down for following this transmission, a Cyclic Redundancy Code (CRC) 18 or some other form of corruption check and constant modulated carrier 19 for ranging.
The target unit receives the synchronisation signal 15, address 16, time code 17 and CRC 18.
If the CRC is correct and the address matches its own, the target unit switches on its transmitter ash shown by 20 for the duration of the ranging signal enabling the measurement unit to determine its range. It then powers down for a period defined by the time code which will have been set by the measurement unit so that the target wakes up just before the next transmission addressed to it.
If the measurement unit detects that the channel is busy at the time that it is scheduled to make a transmission burst, it cancels the burst, relying on the fact that bursts are sufficiently frequent that a missed burst is not serious. If a collision does occur, both targets will detect a CRC error and hence will not generate a ranging signal. The measurement units can detect this condition and ignore any range data for that burst.
The invention can be used to create a distance triggered alarm in which an alarm signal is generated if the distance between a measurement and target unit increases or decreases past a threshold. A measurement unit 21 produces an analogue signal varying according to the distance to a target unit 25 as previously described A threshold generator 22 produces a threshold which may be either fixed or derived from the distance signal. The distance signal and threshold are compared in a comparator 23 which can drive an alarm 24 at the measurement unit end of the system. Alternatively or in addition, the alarm state can be transmitted to the target unit using the communication means described above or by deliberately switching off measurement unit transmissions and an alarm generated at the target unit end of the system as shown by 26.The system can be arranged so that a fault or any other condition which results in a loss of received signals from the far-end unit triggers the alarm. This can be used as the basis of tamper-proofing either unit by disabling transmissions if the unit is tampered with.
An example of an application of the invention is in the protection of possessions such as briefcases, luggage, handbags, personal organisers, cash-bags or other containers carried with the person. The person 27 carries a measurement unit 28 which measures the distance to a target unit 30 fitted within or attached to the item to be protected 29. If the separation r exceeds a threshold of for instance a few meters, then an alarm sounds at the measurement unit alerting the person to the situation. Multiple items can be protected by making use of the multiple target unit capability of the measurement unit and fitting the additional items to be protected 31 with further target units. A different form of protection can be afforded by fitting an alarm at the target unit in addition to or in place of the alarm at the measurement unit.
A further application of the invention is in child minding where the minder 32 carries a measurement unit 28 and the child to be minded 33 carries a target unit 30. An alarm is sounded at the measurement unit if the child strays so that the distance r exceeds a set value.
Further children 34 can be accommodated using the same measurement unit.
A further application of the invention is in electronic detention systems where a detainee 35 is fitted with a target unit 30. If the distance r exceeds a set value, the measurement unit 28 automatically sounds an alarm or informs a remote site via some connection 36. The target unit can be made in such a way that if it is removed or tampered with, it ceases to respond to measurement unit interrogations. The measurement unit can detect this condition and raise an alarm.
A further application of the invention is the protection of unattended goods, pieces of equipment or belongings. The item to be protected 31 is fitted with a target unit 30. If the distance to a fixed measurement unit 28 changes by greater than an allowed limit the measurement unit can sound an alarm or inform a remote site via some connection 36. The target unit can be made in such a way that if it is removed or tampered with, it ceases to respond to measurement unit interrogations. The measurement unit can detect this condition and raise an alarm.
A further application of the invention is in local area positioning and tracking. A unit requiring knowledge of position 38 is fitted with a measurement unit 28 and operates within range of one or more target units 30. By measuring the range to each target unit and according to the number of target units, the position in 1, 2 or 3 dimensions can be determined. If measurement and target units are transposed, a tracking system is realised instead of a positioning system.
Claims (10)
1. A method of distance measurement using sub-microwave radio frequency signals in
which the distance between a measurement unit and a co-operative active target unit is
determined as follows: The measurement unit transmits a carrier signal which is
frequency modulated with a low frequency modulation signal; This is received by the
target unit which applies a small frequency shift to the signal and re-transmits it; The
measurement unit receives the frequency shifted signal and mixes it with its
transmitted signal to form a further frequency modulated signal in which the carrier
frequency is equal to the frequency shift applied by the target unit and the modulation
signal is at the frequency of the transmitter modulation and takes a form dependent on
the round trip delay between measurement and target units and hence distance.
2. Distance measurement from a measurement unit to a target using continuous wave
frequency modulation of radio frequencies where an active target unit is used which
receives a signal from the measurement unit, shifts it in frequency and re-transmits it.
3. Distance measurement as claimed in claim 2 where the modulation signal is used to
provide a communication means between the measurement unit and the target unit.
4. Distance measurement as claimed in claim 3 where the communication means is used
to allow multiple targets to be addressed by a single measurement unit or to provide
for co-located operation of measurement systems on the same frequency.
5. Distance measurement as claimed in claims 2, 3 or 4 where the measurement is used
to provide a distance related alarm
6. Application of the inventions claimed in claims 2, 3 or 4 for the protection of
possessions carried with the person, specifically including briefcases, luggage,
handbags, personal organisers, cash-bags and other containers.
7. Application of the inventions claimed in claims 2, 3 or 4 as a child straying alarm.
8. Application of the inventions claimed in claims 2, 3 or 4 as part of an electronic
detention system.
9. Application of the inventions claimed in claims 2, 3 or 4 for the protection of
unattended goods, pieces of equipment or belongings.
10. Application of the inventions claimed in claims 2, 3 or 4 in positioning or tracking
systems.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9009510A GB2243739A (en) | 1990-04-27 | 1990-04-27 | Frequency modulation distance measurement of active target |
| GB9103079A GB2246891A (en) | 1990-04-27 | 1991-02-13 | Alarm system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9009510A GB2243739A (en) | 1990-04-27 | 1990-04-27 | Frequency modulation distance measurement of active target |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9009510D0 GB9009510D0 (en) | 1990-06-20 |
| GB2243739A true GB2243739A (en) | 1991-11-06 |
Family
ID=10675109
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9009510A Withdrawn GB2243739A (en) | 1990-04-27 | 1990-04-27 | Frequency modulation distance measurement of active target |
| GB9103079A Withdrawn GB2246891A (en) | 1990-04-27 | 1991-02-13 | Alarm system |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9103079A Withdrawn GB2246891A (en) | 1990-04-27 | 1991-02-13 | Alarm system |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB2243739A (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2738968A1 (en) * | 1995-09-19 | 1997-03-21 | Thomson Csf | METHOD FOR LOCATING A DATA PACKET TRANSCEIVER AND TRANSCEIVER USING THE SAME |
| WO1997027498A1 (en) * | 1996-01-26 | 1997-07-31 | Thomson-Csf | Method for determining the direction of a radiocommunication emitter-receiver, and emitter-receiver implementing said method |
| FR2783955A1 (en) * | 1998-09-25 | 2000-03-31 | Richard Hamon | Master/slave transmitter/receiver set object/person absence alerting having slave retransmitting coded transmissions and master detecting signal absence/sounding alarm. |
| DE19946161A1 (en) * | 1999-09-27 | 2001-04-26 | Siemens Ag | Distance measurement method |
| NL1028429C2 (en) * | 2005-03-01 | 2006-09-06 | Nedap Nv | Detection system for person lost at sea, uses RF label in clothes or lifejacket to reflect radar signal modulated with sub carrier wave frequency |
| AT414178B (en) * | 2003-05-05 | 2006-09-15 | Werner Dipl Ing Dietrich | METHOD AND DEVICE FOR MARKING DISTANCE LIMITS |
| GB2442778A (en) * | 2006-10-12 | 2008-04-16 | Philip James Smith | Portable security system for preventing two or more objects being separated by more than a predetermined distance |
| ITPI20080139A1 (en) * | 2008-12-31 | 2010-07-01 | Ids Ingegneria Dei Sistemi S P A | METHOD FOR INTERFEROMETRIC RADAR MEASUREMENTS |
| WO2011046436A1 (en) | 2009-10-14 | 2011-04-21 | Nederlandse Organisatie Voor Toegepast-Natuurwetenschappeliijk Onderzoek Tno | Fmcw distance measuring method and devices |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5589821A (en) * | 1994-12-13 | 1996-12-31 | Secure Technologies, Inc. | Distance determination and alarm system |
| GB2314986A (en) * | 1996-07-02 | 1998-01-14 | Alan Michael Cox | Electronic child protection system |
| US6812824B1 (en) | 1996-10-17 | 2004-11-02 | Rf Technologies, Inc. | Method and apparatus combining a tracking system and a wireless communication system |
| AU5426298A (en) * | 1996-10-17 | 1998-05-11 | Pinpoint Corporation | Article tracking system |
| GB2333876A (en) * | 1998-02-02 | 1999-08-04 | Anthony John Hulbert | Mobile range sensitive security device |
| FR2776101B1 (en) * | 1998-03-11 | 2000-09-15 | Gerard Gary | PORTABLE DEVICE FOR CONTROLLING THE PRESENCE OF AN OBJECT SPECIFICALLY MARKED FOR THIS PURPOSE, IN AN AREA RELATED TO THE DEVICE |
| GB2344914A (en) * | 1998-06-18 | 2000-06-21 | Paul Anthony Delahunty | System for protecting an article or child |
| GB9917490D0 (en) * | 1999-07-27 | 1999-09-29 | Activerf Ltd | Improvements relating to security |
| GB2375424A (en) * | 2001-05-08 | 2002-11-13 | Lee Stephen Duffett | Personal items protection alarm |
| US8088044B2 (en) | 2008-03-03 | 2012-01-03 | Nike, Inc. | Interactive athletic equipment system |
| US8231506B2 (en) | 2008-12-05 | 2012-07-31 | Nike, Inc. | Athletic performance monitoring systems and methods in a team sports environment |
| US8628453B2 (en) | 2008-12-05 | 2014-01-14 | Nike, Inc. | Athletic performance monitoring systems and methods in a team sports environment |
| US8172722B2 (en) | 2008-12-05 | 2012-05-08 | Nike, Inc. | Athletic performance monitoring systems and methods in a team sports environment |
| WO2012064956A1 (en) | 2010-11-10 | 2012-05-18 | Nike International Ltd. | Systems and methods for time-based athletic activity measurement and display |
| EP2676213B1 (en) | 2011-02-17 | 2019-07-31 | NIKE Innovate C.V. | Location mapping |
| ITBO20110562A1 (en) * | 2011-10-03 | 2013-04-04 | Calzati Andrea Ditta Individuale | METHOD OF SURVEILLING PERSONAL ITEMS AND CORRESPONDING SYSTEM OF SURVEILLANCE |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1219410A (en) * | 1967-06-16 | 1971-01-13 | Standard Telephones Cables Ltd | Radio navigation equipment |
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| US3924065A (en) * | 1974-04-05 | 1975-12-02 | Information Identification Inc | Coherent, fixed BAUD rate FSK communication method and apparatus |
| US4177466A (en) * | 1977-11-16 | 1979-12-04 | Lo-Jack Corporation | Auto theft detection system |
| CA1277400C (en) * | 1986-04-09 | 1990-12-04 | Uri Rapoport | Anti-theft and locating system |
| HUT43774A (en) * | 1986-05-15 | 1987-11-30 | Koezponti Banyaszati Fejleszte | Method and apparatus for automatic identification living beings and objects |
| GB2207787B (en) * | 1987-08-06 | 1991-10-30 | James Terence Barker | Retrieval of lost road vehicles and other articles |
| GB8924743D0 (en) * | 1989-11-02 | 1989-12-20 | Security Alert Ltd | Electronic systems for the protection of articles |
-
1990
- 1990-04-27 GB GB9009510A patent/GB2243739A/en not_active Withdrawn
-
1991
- 1991-02-13 GB GB9103079A patent/GB2246891A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1219410A (en) * | 1967-06-16 | 1971-01-13 | Standard Telephones Cables Ltd | Radio navigation equipment |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2738968A1 (en) * | 1995-09-19 | 1997-03-21 | Thomson Csf | METHOD FOR LOCATING A DATA PACKET TRANSCEIVER AND TRANSCEIVER USING THE SAME |
| EP0764854A1 (en) * | 1995-09-19 | 1997-03-26 | Thomson-Csf | Method for determining the position of an emitter-receiver for data packets and emitter-receiver using the method |
| US5712639A (en) * | 1995-09-19 | 1998-01-27 | Thomson-Csf | Method for the localizing of a transceiver of data packets |
| WO1997027498A1 (en) * | 1996-01-26 | 1997-07-31 | Thomson-Csf | Method for determining the direction of a radiocommunication emitter-receiver, and emitter-receiver implementing said method |
| FR2744223A1 (en) * | 1996-01-26 | 1997-08-01 | Thomson Csf | METHOD FOR DETERMINING THE LEADERSHIP OF A RADIO COMMUNICATION TRANSCEIVER AND TRANSCEIVER IMPLEMENTING THE METHOD |
| FR2783955A1 (en) * | 1998-09-25 | 2000-03-31 | Richard Hamon | Master/slave transmitter/receiver set object/person absence alerting having slave retransmitting coded transmissions and master detecting signal absence/sounding alarm. |
| DE19946161A1 (en) * | 1999-09-27 | 2001-04-26 | Siemens Ag | Distance measurement method |
| AT414178B (en) * | 2003-05-05 | 2006-09-15 | Werner Dipl Ing Dietrich | METHOD AND DEVICE FOR MARKING DISTANCE LIMITS |
| NL1028429C2 (en) * | 2005-03-01 | 2006-09-06 | Nedap Nv | Detection system for person lost at sea, uses RF label in clothes or lifejacket to reflect radar signal modulated with sub carrier wave frequency |
| GB2442778A (en) * | 2006-10-12 | 2008-04-16 | Philip James Smith | Portable security system for preventing two or more objects being separated by more than a predetermined distance |
| ITPI20080139A1 (en) * | 2008-12-31 | 2010-07-01 | Ids Ingegneria Dei Sistemi S P A | METHOD FOR INTERFEROMETRIC RADAR MEASUREMENTS |
| WO2010076037A1 (en) | 2008-12-31 | 2010-07-08 | Ids Ingegneria Dei Sistemi S.P.A. | Method for interferometric radar measurements |
| WO2011046436A1 (en) | 2009-10-14 | 2011-04-21 | Nederlandse Organisatie Voor Toegepast-Natuurwetenschappeliijk Onderzoek Tno | Fmcw distance measuring method and devices |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2246891A (en) | 1992-02-12 |
| GB9103079D0 (en) | 1991-03-27 |
| GB9009510D0 (en) | 1990-06-20 |
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