Ultrasound zone location system with high capacity

摘要

A zone location system with ultrasound US transmitters S1, S2, S3 located in respective zones Z1, Z2, Z3 such as rooms of a building B. Preferably, the US transmitters are time-multiplexed so that each of them in turn transmits a US signal US with a unique ID code USID represented therein. The portable tag PT includes an ultrasound receiver USR arranged to receive the US signal. Based on the received US signal, the portable tag PT measures a strength of the received US signal. The portable tag PT also measures a parameter related to a movement of the portable tag PT, e.g. a Doppler shift based on the received US signal. Further, the portable tag extracts the USID. Then it transmits a wireless Radio Frequency signal RFS with its own ID PTID, the USID and first and second data values D1, D2 representing the signal strength and the movement related parameters. A processor P connected to a Radio Frequency receiver RFR receives the data from the portable tag PT and determines a connection between PTID and the zone Z2 in which it is present based on the USID. Further, the processor utilizes data D1 and D2 to calculate an estimated position POS within the zone Z2. Especially, estimated distance between US transmitter S2 and portable tag PT and velocity of the portable tag may be estimated based on D1 and D2, thus assisting in estimating the position POS of the portable tag PT. The system may further be combined with a Radio Frequency based positioning system, e.g. an RF signal strength based system, thereby enhancing the resolution of the estimated position POS of the portable tag PT. Further, such combined system help location in complicated and changing environments and in situations where the portable tag PT may be out of reach for US signals, e.g. when attached to a paper file enclosed in a box.