Abstract:
The invention relates to a system for transferring information closely connected to an object. The system is characterized in that it comprises a conductor arrangement, which comprises a number of conductor components, that forms an electromagnetic field, as well as a transmitter associated with the object. The aforementioned transmitter is arranged to connect by means of an electromagnetic field to the conductor arrangement and also to modulate the measuring signal formed by means of the field.

Description:
FIELD OF THE INVENTION 
     The object of this invention is a method and a system, based on near-field measurement, for transferring information. 
     STATE OF THE ART 
     In prior-art indoor position location systems, which are based on a radio frequency, ultrasound frequency or infrared frequency measurement of delay or power, it is possible to locate and identify an object by means of a portable transponder or corresponding. Systems that operate by means of a transponder are in this context called active position location systems. Of these, only systems that operate at infrared frequencies also work without a transponder, i.e. as passive systems. In this case identification does not succeed and position location measurement is only at the movement detection level. In this case the changes in IR power between rough sectors are measured. Indoor position location systems that operate without a transponder are called in this context passive position location systems. These types of systems comprise electret films, force sensor matrixes or pressure sensor matrixes, and position location measurement based on an electromagnetic near field. The advantage of film sensors, pressure sensors or near field sensors compared to active indoor position location systems is e.g. they do not need a portable transponder, or corresponding, for the position location function in order to operate. In addition, their range of coverage is not limited by reflections or shadow areas. 
     Active position location systems thus always require a portable transmitter in order to operate. In addition, the range of coverage of active systems is limited in indoor spaces by reflections and shadow areas. The aforementioned passive indoor position location methods do not require a transponder, nor do coverage problems occur in them. A problem with state-of-the-art passive systems is, however, that they do not enable identification of the object. 
     Some state-of-the-art systems are described in more detail e.g. in the following publications:
     Hyunggi Cho, Myungseok Kang, Jonghyuk Park, Byungsung Park and Hagbae Kim.  Performance Analysis of Location Estimation Algorithm in ZigBee Networks using Received Signal Strength . 21st International Conference on Advanced Information Networking and Applications Workshops (AINAW&#39;07) 2007.   Ward, A., Jones, A. and Hopper, A.  A New Location Technique for the Active Office . IEEE Personal Communications, Vol. 4, No. 5, October 1997. pp. 42-47.   Want, R., Hopper, A., Faleao, V. and Gibbons, J.  The Active Badge Location System . Transactions on Information Systems, Vol. 10, No. 5, January 1992, pp. 42-47.   Kirjavainen, K.  Electromechanical Film and Procedure for Manufacturing Same . U.S. Pat. No. 4,654,546, 1987.   Lekkala, Jukka and Paajanen, Mika. EMFi— New Electret Material for Sensors and Actuators . 10th International Symposium on Electrets, 1999.   Addlesee, Michael D., Jones, Alan., and Ivesey, Finnbarl.  The ORL Active Floor . IEEE Personal Communications, Vol. 4, No. 5, October 1997, October 1997. pp. 35-41.   Murakita, Takuya, Ikeda, Tetsushi, and Ishiguro, Hiroshi.  Human Tracking using Floor Sensors based on the Markov Chain Monte Carlo Method . Proceedings of the 17th International Conference on Pattern Recognition, 2004.   Sepponen, Raimo.  Method and Arrangement for Observation . International Patent Application No. W02004F100489 20040820, 2005. U.S. Patent Application No. 2007008145, 2007.   Rimminen, Henry, Linnavuo, Matti, and Sepponen, Raimo.  Human Tracking Using Near Field Imaging . Proceedings of Pervasive Health 2008, Tampere, Finland.   

     BRIEF DESCRIPTION OF THE INVENTION 
     The invention presents an indoor position location system based on the measurement of an electromagnetic near field and a method that identifies its object, in addition to locating the position, and transfers information relating to the identified object between the object of the position location and the position location system. 
     The system according to the invention for transferring information closely connected to an object in an electromagnetic field is characterized in that the system comprises a conductor arrangement, which comprises a number of conductor components, that forms an electromagnetic field, and also a measuring arrangement, with which the system forms a measuring signal according to the field, and also transmitter associated with the object, and the aforementioned transmitter is arranged to connect by means of an electromagnetic field to the conductor arrangement and also to influence the measuring signal formed by the system according to the field. 
     The conductor arrangement of the invention can comprise e.g. printed conductor patterns. 
     The system can further comprise means for forming a measurement signal by means of impedance. The impedance of a conductor pattern can be measured in relation to the impedance of the whole conductor arrangement. The object can be located e.g. by identifying the measuring signal and at least one conductor pattern that participated in forming the signal. 
     The system can further comprise means for locating the position of an object in the area of the aforementioned conductor arrangement and position location system. 
     The position location system according to some embodiments of the invention can comprise means for measuring the impedance of at least one aforementioned conductor component and of the whole aforementioned conductor arrangement. 
     The transmitter according to some embodiments of the invention can comprise means for ASK modulation of the aforementioned measuring signal. 
     The transmitter can be connected to the object such that it connects by means of an electromagnetic field to the conductor component (conductor pattern) to be measured, and also via impedance to the object to be located. 
     In the case of an electrical field the conductor surface can function as the connection element of the electromagnetic field from the conductor component to the transmitter and/or to the object from the transmitter. In the case of a magnetic field a loop can function as the connection element. 
     The transmitter can influence the electromagnetic connection between the conductor component to be measured and the object with the control means of the transmitter, which can be e.g. a transistor, a switch, a resonator or a filter. 
     The transmitter according to the invention can comprise means for activation of the transmitter in the aforementioned electromagnetic field. 
     A position location system, which can comprise e.g. an apparatus for analyzing the measuring signal, can be connected to the system. The position location system can identify a located object or receive information closely connected to the object on the basis of the modulated measuring signal e.g. by demodulating the modulated measuring signal that it receives. 
     An exemplary position location system applicable to the use of the invention is described in the reference (Sepponen, Raimo.  Method and Arrangement for Observation . International Patent Application No. W02004F100489 20040820, 2005. U.S. Patent Application No. 2007008145, 2007) 
     The invention also relates to a method for identifying an object and/or locating the position of the object with the means of the system according to the invention. 
    
    
     
       DETAILED DESCRIPTION OF THE INVENTION 
       In the following the invention will be described in more detail with reference to some preferred embodiments presented as examples and to the attached drawings, wherein 
         FIG. 1  presents one embodiment of the arrangement used in the invention, 
         FIG. 2  presents one embodiment of the transmitter according to the invention and 
         FIG. 3  presents one exemplary application of the invention. 
     
    
    
       FIG. 1  presents a position location system and identification system, which is based on near-field measurement, according to one embodiment of the invention. The position location system ( 101 ) measures the electromagnetic connection of the conductor pattern ( 102 ), which is installed under the floor surface, to the conductor pattern group ( 103 ). In other words, the system ( 101 ) measures the impedance ( 104 ) of one conductor pattern ( 102 ) in relation to the whole conductor pattern group ( 103 ) with a spot frequency or with a variable frequency. The conductor patterns form a conductor matrix, the impedance ( 104 ) of each element of which in relation to the whole matrix is measured alternately. When an object ( 105 ) possessing sufficient conductivity is in the proximity of the conductor pattern, the impedance to be measured decreases, which is registered as the presence of the object ( 105 ). The plurality of objects to be observed with the method includes, among others, people, animals, robots, metal furniture, and also different machines and vehicles. When a transmitter ( 106 ) according to some embodiments of the invention is connected to the object, the object can be identified from the measured signal. 
     A transmitter according to one embodiment of the invention is presented in  FIG. 2 . The transmitter ( 206 ) is connected to the object such that is connects electromagnetically to the conductor pattern ( 202 ) to be measured, and also to the object ( 205 ) to be located via impedance ( 208 ). The transmitter regulates the electromagnetic connection between the conductor pattern ( 202 ) to be measured and the object ( 205 ) with control means ( 207 ), which can be e.g. a transistor, a switch, a resonator or a filter. The object, for its part, connects to all the rest of the conductor matrix ( 203 ) via impedance ( 209 ). By means of the regulation the total impedance of the object visible in the measurement is converted or modulated such that the information is transferred from the transmitter ( 206 ) via the electromagnetic field for the position location system ( 201 ) to read. The information to be transferred can be e.g. the identifier or some other information of the transmitter ( 206 ). An interface means ( 210 ), e.g. a switch or a movement detector, can be connected to the transmitter, by means of which interface the transmitter can e.g. be activated to modulate the measuring signal received by the position location system ( 201 ). 
     The transmitter can be associated with an object e.g. by installing a transmitter in the footwear, clothing accessories, frame of the object, the casing of the object or the body of the object. The transmitter can be connected to the object e.g. by installing it into footwear in the manner illustrated in  FIG. 3 . The position location system ( 301 ) based on near-field measurement measures the impedance of the conductor plate ( 302 ) in relation to the whole conductor plate group ( 303 ) by supplying alternating current ( 311 ) to one conductor plate, and by measuring the strength ( 312 ) of the current. A conductor area is installed in the footwear ( 323 ) in the sole ( 314 ), which is insulated from the floor with a wearing surface ( 313 ). The electrical field is connected ( 308 ) to the conductor area ( 314 ), which for its part is connected with a conductor ( 315 ) to the transmitter ( 306 ), such as to e.g. a microcontroller. The microcontroller, which operates e.g. by means of a battery ( 316 ), modulates the measuring signal e.g. by interrupting the current passing through it with a transistor switch ( 307 ). The data to be modulated is retrieved from the memory ( 317 ) of the micro-controller. The microcontroller is connected, e.g. through the sole material ( 318 ) of the footwear, with a conductor ( 319 ) to the conductor area ( 320 ), which is fixed to a conducting or insulating insole ( 321 ). From here the current is connected ( 322 ) to the sole of the person using the footwear, from where there is a galvanic path to the whole object, e.g. to the body ( 305 ) of the person using the footwear. The body of the person, for its part, is connected ( 309 ) to the conductor plates ( 303 ) that function as a return path of the current, in which case the loop ( 324 ) to the voltage source closes. Now the transistor switch ( 307 ) of the transmitter, which is a part of the loop, converts or modulates the signal visible with a current meter and transfers the identifier or some other information of the transmitter to the position location system. The impedance is converted e.g. by using ASK modulation (amplitude-shift keying), which is well known to those skilled in the art. Now the person wearing the footwear can be identified and also, if desired, located. If a transmitter is not associated with an object, however, the object can always be located although not identified. 
     By means of the different embodiments of the invention presented, the problems of active position location systems can be resolved by adding an identification function to a passive position location system. The invention can thus enable transfer of the identification and other information of the object of position locating between the object and the position location system using a passive position location system based on near-field measurement. The information to be transferred is included in the measuring signal to be used in the position location by modulating it. 
     Likewise it is also obvious to the person skilled in the art that the exemplary embodiments presented above are for the sake of clarity comparatively simple in their structure and function. Following the model presented in this patent application it is possible to construct different and also very complex solutions that utilize the inventive concept presented in this patent application.