Abstract: Systems and methods for use in reading and locating passive RFID tags. A reader/locator system sends out a signal with varying frequency. A tag reflects the signal back and the receiver portion of the reader/locator system receives the signal after a certain propagation delay. Since during this propagation delay the transmit frequency has changed, the received signal frequency differs from the one is currently transmitted. The received signal gets mixed with the currently transmitted signal and the resulting beat frequency depends on the frequency variation pattern (which is known) and the signal propagation delay. This beat frequency is directly proportional to the distance between the reader/locator and the RFID tag. The beat frequency can therefore be used to estimate this distance between the reader/locator and the RFID tag.

Abstract: A portable hand-held computer device comprises a base (10) and a hinged support (12A,12B,34) pivotal between a closed position lying against the base, and an open position extending perpendicularly from the base. A microdisplay (16) attached to the distal end of the support provides a virtual display measuring between, for example, 9 inches and 19 inches diagonally. The base unit (10) houses a microcomputer (90), which drives the microdisplay (16), and a mobile telephone unit (92). Controls (42,46) and a touch-sensitive pad (48) for operating the microcomputer (90) are provided on an upper face of the base (10). The touch-sensitive pad (48) may be an overlay upon a second display which is used to display mobile telephone information. Part (34) of the support carries a set of mobile telephone controls (36) for use when the device is closed and the part (34) obscures the microcomputer controls (42,46). The device may be used with a docking station (13) in a vehicle.