Abstract: A transmitter device (1), operable to perform distance measurements by using time-of-flight measurements, has a sampling frequency different to the frequency of a time-of-flight signal sent from the transmitter device to a receiver device (12) in order for the distance between the transmitter device (1) and the receiver device (12) to the determined. The signal, from which the time-of-flight signal is derived, is modulated with a PRN sequence derived from the output signal of a Numerically Controlled Oscillator (17). A new chip is generated by the NCO (17) each time a register (24) in the NCO overflows, but the beginning of the chip according to the desired frequency of the PRN code does not necessarily coincide with a sampling point in the transmitter device (1).

Abstract: Method for obtaining range and/or positional information of electronic devices typically rely on a device (A) re-questing that another device (B) supplies a reply message (22), which contains some timing information (T2, T3) on the signals received and sent. Problems that arise in such networks comprise: firstly, some devices (C) may be out of range of the device (A) that initiates the ranging measurements, and secondly, some devices (B, C) may not be allowed to communicate with each other and thus, the distance between these devices cannot be found. This invention discloses that in these cases, eavesdropping on messages (21, 22, 24) passing between other devices (A, B, C) in the system can result in that distances between additional devices are found. Furthermore, by using eavesdropping the number of transmissions, and therefore the potential for collisions, is reduced. Thus, the power consumption of the nodes in the network can be lowered.

Abstract: A wireless activation system, such as a keyless car entry system, uses repeated code sequences (mk) for communication between a transmitter device (400) and a receiver device (200). By varying the sequence duration in a synchronism at the transmitter device and receiver device, either by varying the number of symbols or chips in the sequence, or by varying the symbol or chip rate, it is made more difficult for an unauthorised party to detect the code sequences and relay the code sequences to achieve unauthorised activation at the receive device (200).

Abstract: The method and apparatus are for use in a building (2) having walls (8) and corridors (10) extending longitudinally (4) and laterally (6). Base stations (20, 22) have antennae orientated with a cosec2 pattern longitudinally (4) and laterally (6) and range a mobile station (26) to determine its position.

Abstract: A device (200) measures distance using a wireless signal that comprises two simultaneously transmitted components. Each of the two components comprises a respective repeated code, the two codes having different durations. On receipt of the signal, the propagation distance is calculated separately for each code and compared (280). The calculated distance is considered to be valid only if the two calculations yield the same result. Preferably the durations of the two codes are proportional to numbers having a relative prime relationship. The signal is generated and transmitted by the same device (200) that performs the distance calculation, with the signal being retransmitted back to the device by a remote device (100), or may be generated and transmitted by the remote device (100).

Abstract: A signal receiver suitable for digitising a signal having a wide bandwidth comprises a filter bank (30) for dividing a received signal into a plurality of frequency sub-bands, means (41-45) for digitising each sub-band using a low sample rate, means (51) for transforming each digitised sub-band signals into the frequency domain, means (61-65, 70) for concatenating the frequency domain sub-band signals to reconstruct the spectrum of the received signal. For a signal that occupies only one sub-band at any one instant, for example a frequency hopping signal or a chirp signal, a single analogue-to-digital converter may be used to digitise each sub-band in turn, and the transformation into the frequency domain may be performed for each sub-band in turn.