| 摘要 |
An access unit 23 for communicating with a further access unit 5 to control access to a vehicle comprises a first ultra-wideband (UWB) transmitter 25 for transmitting a polling signal and a first UWB receiver 25 for receiving an authentication signal from the further access unit in response to the polling signal. The further access unit may have a second UWB receiver 11, 13, 15 to receive the polling signal from the access unit and a second UWB transmitter 11, 13, 15 for transmitting the authentication signal to the access unit. Preferably, the access unit is located in a key fob and the further access unit is located in the vehicle. The access unit may transmit a response signal to the further access unit in response to receiving the authentication signal from the further access unit. The polling signal may be a pulsed signal that is continually transmitted, with the interval between pulses being dependent upon the distance between the two access units 5, and 23. The vehicle doors can be unlocked based upon the distance between the two access units 5, and 23. The system is very low power, increasing battery life, and has a fast response time. |
