FR2777357A1 - Alarm position locating transmit or receiver - Google Patents

Abstract

The phase difference measurement between the transmit and receive signals provide an accurate position fixing of the alarm, which can be divided into sectors.

Description

LOCATION SYSTEM
The present invention relates to a location system. The invention relates more particularly to a system making it possible to locate, at least at a short distance and with precision, a living being provided with an appropriate terminal.

 Numerous systems are known which make it possible to trigger an alarm automatically when a person requests assistance or when the latter leaves a surveillance perimeter. These devices are generally triggered when the distance between a mobile terminal and a base station exceeds a predetermined threshold.

 For example, document WO-A-96/18913 describes a distance determination system making it possible to trigger an alarm when a mobile associated with a carrier deviates from a distance greater than a predetermined threshold of a base station .

 A drawback of this system and of the other known systems is that they do not make it possible to find the bearer of the terminal by locating it. This drawback is particularly critical for people with disabilities and in particular with Alzheimer's disease. The latter cannot in fact initiate a request for assistance on their own initiative and can put themselves in conditions that could become dangerous.

 It would be desirable to have a system which makes it possible to automatically alert a responsible person and which allows him to assist the disabled person.

 An object of the present invention is to provide a new system for locating people or animals which does not have the limitations of known systems.

 The present invention also aims to propose such a system which allows the automatic triggering of an alarm according to different criteria and, in particular, according to criteria other than the distance.

 The present invention further aims to provide a system which associates a short distance location with a location independent of the base station.

 A characteristic of the present invention is to associate a detection of the distance separating the transmitter module from the receiver module with a bearing measurement of the transmitter module. These two associated means are active at a short distance (less than 5 km).

 Within the meaning of the present invention, the transmitter module (or to be monitored) is the equipment worn by the disabled person or the animal whose movements one wishes to monitor.

The receiver (or search) module corresponds to the equipment available to the person responsible for this monitoring. Of course, these two pieces of equipment in practice each have transmission and reception functions.

 More particularly, the present invention provides a location system comprising at least one transmitter module capable of receiving and transmitting radio frequency signals at least in response to a reception of radio frequency signals from a receiver module, the receiver module being capable of transmitting and receiving radio frequency signals and comprising means for determining the distance which separates it from the transmitter module and means for determining the bearing of the transmitter module relative to the receiver module.

 According to an embodiment of the present invention, the transmitter module is associated with at least one sensor of a physiological or environmental parameter of a living being to be located and comprises means for transmitting information related to this parameter to the receiver module , said parameter being chosen from heart rate, blood pressure, body temperature, ambient temperature or the acceleration undergone by the transmitter module.

 According to an embodiment of the present invention, a transmission of signals to determine the distance and the bearing of the transmitter module with respect to the receiver module is triggered by exceeding a threshold of said parameter.

 According to an embodiment of the present invention, said radio frequency signals are transmitted by irradiation trains, said information linked to the measured parameter being transmitted by modulation of said pulse trains.

 According to an embodiment of the present invention, each module is adapted to be associated with a mobile telephone network.

 The present invention also relates to a transmitter module suitable for being located on the basis of its radiofrequency transmissions, and which comprises means for transmitting and receiving radio frequency signals and means for transmitting information linked to measurements carried out by means of minus a sensor of a physiological or environmental parameter of a living being with which the module is associated.

The present invention further relates to a receiver module for locating at least one transmitter module, which comprises
means for transmitting and receiving radio frequency signals
means for determining a distance separating it from a transmitter module, the distance measurement being carried out on the basis of a measurement of propagation time of pulse trains transmitted by the receiver module and by the transmitter module; and
means for measuring the bearing of the module to be monitored, the bearing measurement being carried out on the basis of the phase shift between the signals received by two antennas of the receiver module.

These objects, characteristics and advantages, as well as others of the present invention will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which
FIG. 1 represents an embodiment of a receiver module according to the present invention
FIG. 2 represents an embodiment of a transmitter module according to the present invention
FIG. 3 illustrates an embodiment of distance measuring means according to the present invention
FIG. 4 illustrates an embodiment of bearing measurement means according to the present invention; and
FIG. 5 illustrates an embodiment of a system according to the invention associated with an external location network
The same elements have been designated by the same references in the different figures. For reasons of clarity, only the elements which are necessary for the understanding of the invention have been shown and will be described later.

 FIG. 1 represents, in the form of block diagrams, an embodiment of a receiver module 1 according to the present invention. This module comprises a transmission block 11 (Tx), a reception block 12 (Rx), a central unit 13 (UC) for processing the signals received and to be transmitted, and one or more antennas 14.

The choice of one or more antennas 14, 14 'for the receiver module 1 depends, in particular, on the method used for the measurement of bearing as will be seen later. In the case where several antennas 14, 14 ′ are used for the bearing measurement, the module 1 comprises an adaptation network (Sep) 15 between the antennas 14, 14 ′ and the transmit 11 and receive 12 blocks. The module 1 is preferably associated with a display screen 16 (Scr) and a keyboard 17 (K) for entering information.

 FIG. 2 represents an embodiment of a transmitter module 2 according to the present invention. This module 2 comprises, like the receiver module, a transmission block (Tx) 21 and a reception block (Rx) 22 of data, a central processing unit (UC) 23 for processing the transmitted and received data and an antenna 24 transceiver. In a preferred embodiment as shown in FIG. 2, the module 2 also comprises an entity 28 (UA) for acquiring measurement results carried out by sensors 3 (Det) as will be seen below.

 A characteristic of the present invention is that the module 1 can not only detect the distance which separates it from a module 2 to be monitored, but also determine the bearing of this remote module. Thus, according to the invention, the signal processing programs executed by the central unit 13 (and incidentally by the unit 23) and the transmission-reception means of the module 1 (in particular, the antennas 14, 14 ' ) are suitable for a bearing measure.

 According to the present invention, the radio frequency transmissions of modules 1 and 2 are carried out in a pulse mode and not continuously. This has several advantages.

 A first advantage is that the energy consumption is considerably reduced.

 A second advantage is that the range being directly linked to the transmitted power by not taking into account the gains of the different antennas, it is now possible to obtain a transmit power therefore a much greater range while maintaining a low consumption.

 FIG. 3 illustrates an embodiment of a measurement of the distance separating a module 1 and a module 2 according to the present invention.

 FIG. 3 represents, in the form of chronograms, the relationships between the instants of transmission and of reception of a train of pulses transmitted by the receiver module 1 in order to evaluate the distance separating it from the transmitter module 2. In FIG. 3, two timing diagrams have been used to illustrate the presence of pulse trains in modules 1 and 2 respectively.

 The distance measurement is carried out by measuring, within the receiver module 1, the time separating the emission of a train of pulses P1 by this module 1 and the reception by the latter of a train of pulses P2 '. The received pulse train P2 'corresponds to a pulse train P2 sent by the transmitter module 2 following the reception by this module 2 of a pulse train P1' (corresponding to the pulse train P1). The received pulse trains P1 'and P2' have been shown attenuated compared to the transmitted pulse trains P1 and P2 due to the conventional attenuation undergone by the radiofrequency signals during propagation.

 The distance D separating modules 1 and 2 is then deduced by the formula D = 2.c. (T1-T2), where T1 represents the time separating, within module 1, the emission of the train of pulses Pî from the reception of the pulse train P2 ', where T2 represents the time separating, within module 2, the reception of the pulse train P1' from the emission of the return pulse train P2, and where c represents the speed of propagation of electromagnetic waves.

 The implementation, within modules 1 and 2, of a distance measurement as illustrated in relation to FIG. 3 is within the reach of those skilled in the art from the functional indications given above.

 It should be noted that, according to a preferred embodiment of the present invention, the frequency of the modulated signal corresponds to the frequencies used by the telephone networks, for example, 430 MHz, 900 MHz, 1800 MHz. The higher frequencies being the best suited for the modules to be monitored 2 because they allow the use of antennas of small dimensions.

The time interval separating two trains of search pulses by the module 1 is chosen according to the application and, in particular, according to the displacement capacity of the module to be monitored 2, so that the successive distance measurements do not allow module 2 to stray too far from module 1 between two measurements. It is thus always possible to carry out a bearing measurement before the module 2 leaves the coverage area of the search module 1. As a particular example, the rate of the pulse trains is of the order of 2 to 60 seconds. or more. Preferably, it is adjusted as a function of the distance separating the modules 1 and 2 and relative to the speed of variation of this distance.

 Preferably, the distance measurement by the module 1 is associated with a distance threshold triggering an alarm. This distance threshold is adjustable by the user as a function of the maximum distance of clearance that he authorizes to module 2.

 According to a preferred embodiment, a second distance threshold is used by the module 1 in order to detect an output of the module 2 from the coverage area or a malfunction of the distance measurement. This second threshold is temporal, that is to say that from the moment of transmission of a train of pulses P1 by the module 1, if this module 1 has not received a train in return of pulses P2 ′ at the end of a predetermined duration, it is considered that the module 2 has left the coverage area or that there is a malfunction.

 An essential difference between the first and second thresholds is that the first threshold is interpreted after reception of the train of pulses P2 ′, that is to say once the distance has been able to be measured, while the second threshold is interpreted by the failure to receive a return pulse train.

 Preferably, distance measurement is used to adapt the transmission powers of modules 1 and 2 so as to minimize their energy consumption.

 According to the invention, the distance measurement is associated with a bearing measurement. This bearing measurement can be triggered at each distance measurement pulse train or, alternatively, be triggered only when the distance separating the finder 1 and monitor 2 modules exceeds the first distance threshold set by the user .

 According to a first embodiment not shown, the bearing measurement is carried out by reehering a zero or a maximum reception by means of a directive antenna 14 of module 1.

The implementation of such a bearing measurement technique is within the reach of the skilled person.

 According to a second embodiment illustrated in FIG. 4, this measurement of bearing is carried out by measuring the phase shift of the signals received by two antennas 14 and 14 ′ by an interferometry measurement.

 FIG. 4 very schematically represents a search module 1 provided with two antennas 14, 14 ′ and a module 2 to be monitored. The bearing measurement is carried out by determining the phase shift, that is to say the time At of additional propagation of the signal emitted by the module 2 in the direction of the module 1 depending on whether it is received by the antenna 14 or by the 14 'antenna. By knowing the distance d separating the antennas 14 and 14 ′, the orientation O of the module 2 is deduced with respect to the module 1.

 The bearing measurement is preferably carried out on the basis of pulse trains (P2, FIG. 3) emitted by the module 2 in return to distance measurement pulse trains (P1) emitted by the module of Research 1. As already indicated above, the bearing measure may, if necessary, only be triggered as soon as a first distance threshold is exceeded.

 The search module 1 therefore now has not only the distance which separates it from the module 2 but also the bearing of this module 2 relative to the search module.

 Another characteristic of the invention is that the module to be monitored receives results of measurements carried out by at least one sensor or detector with which it is associated.

 According to a first embodiment of the search system of the invention, information linked to the parameters measured by the detectors (3, FIG. 2) are transmitted to the search module 1 at each distance measurement. This information is, for example, transmitted in the form of a modulation of the pulses P2 of the distance measuring means.

 According to another embodiment, the parameters detected by the sensors 3 are interpreted directly by the module 2 and the information related thereto is only transmitted to the search module 1 when a threshold containing one of the parameters is exceeded and requires to warn the surveillance person.

 As an example of a parameter that can be monitored by means of the detectors 3, note the heart rate, the blood pressure, the body temperature, the ambient temperature, etc.

 In certain applications, it may be interesting to know whether the movements of the module to be monitored suddenly change speed. To do this, it will be possible to use a device measuring the accelerations as a detector 3 associated with the module 2. As a variant, it will also be possible to store within module 1 several successive distance measurements in order to determine an evolution of the speed of the module to monitor.

 FIG. 5 very schematically illustrates an embodiment of the present invention applied to a combination of direct location with location by means of an external network, for example a mobile telephone network.

 According to this embodiment, as soon as the module to be monitored 2 escapes from the control zone (coverage area) determined by the maximum range of the search module / module to be monitored pair, the modules 1 and 2 are automatically connected to an external network (eg mobile phone). They are then considered as subscribers.

 Such a network generally consists of a multitude of base stations 4 defining a mesh of cells Ci inside which each subscriber can be located. The location of the cell in which a subscriber is located and the management of the passage from one cell to another is carried out, in a conventional manner, by a management system of the telephone network 5.

 The finder module 1 uses the information communicated by the telephone network on the cell in which the module 2 is located so as to virtually extend its range.

We then lose the distance and bearing information at short distance but we know in which geographical area ((cell) the transmitter module is located. To find the distance and bearing information, we bring the search module to this area .

 An advantage of the present invention is that it makes it possible to carry out, in a simple manner, a measurement of distance and bearing, allowing the monitoring of a person or an animal or any mobile object at a short distance.

 Another advantage of the present invention is that, associated with a network system of the mobile telephone type, it makes it possible to supplement this search for location at a short distance by a search for a higher distance.

 Another advantage of the present invention is that, by the techniques chosen for carrying out the distance and bearing measurements, it applies particularly well to small portable and battery-powered systems, in particular as regards relates to the module to be monitored.

 Of course, the present invention is susceptible of various variants and modifications which will appear to those skilled in the art. In particular, the practical realization of the research modules and to monitor is within the reach of the skilled person from the functional indications given above. It will be noted that, although reference has often been made in the foregoing description to a vocabulary adapted to analog technologies to explain the operation of the invention, the latter may be implemented by systems using exclusively techniques digital. In addition, the same search module can be adapted to locate several separate modules to be monitored.

Claims (7)

 1. Localization system, characterized in that it comprises at least one transmitter module (2) suitable for receiving and transmitting radio frequency signals at least in response to reception of radio frequency signals from a receiver module (1 ), the receiver receiver module (1) being suitable for transmitting and receiving radio frequency signals and comprising means (13) for determining the distance (D) which separates it from the transmitter module and means (13) for determining the bearing of the transmitter module compared to receiver module.  2. System according to claim 1, characterized in that the transmitter module (2) is associated with at least one sensor (3) of a physiological or environmental parameter of a living being to be located and comprises means (23, 28 ) to transmit information related to this parameter to the receiver module (1), said parameter being chosen from heart rate, blood pressure, body temperature, ambient temperature or acceleration experienced by the transmitter module.  3. System according to claim 2, characterized in that a transmission of signals to determine the distance and the bearing of the transmitter module (2) relative to the receiver module (1) is triggered by exceeding a threshold of said parameter.  4. System according to claim 2 or 3, characterized in that said radio frequency signals are transmitted by pulse trains, said information related to the measured parameter being transmitted by modulation of said pulse trains.  5. System according to any one of claims 1 to 4, characterized in that each module is adapted to be associated with a mobile telephone network.  6. Transmitter module (2) capable of being located on the basis of its radiofrequency transmissions, characterized in that it comprises means (21, 22, 24) for transmitting and receiving radiofrequency signals and means (23, 28) for transmitting information linked to measurements made by means of at least one sensor (3) of a physiological or environmental parameter of a living being with which the module is associated.  7. Receiver module (1) for locating at least one transmitter module (2), characterized in that it comprises  means (11, 12, 14) for transmitting and receiving radiofrequency signals;  means (13) for determining a distance separating it from a transmitter module (2), the distance measurement being carried out on the basis of a measurement of propagation time (T1) of pulse trains (P1) transmitted by the receiver module (1) and by the transmitter module (2); and  means (13) for measuring the bearing of the module to be monitored, the bearing measurement being carried out on the basis of the phase shift between the signals received by two antennas (14, 14 ') of the receiver module.