Method for measuring distance between two objects and method for controlling access to an object or the use thereof, in particular access control and driving authorization for a motor vehicle

摘要

A bidirectional dialogue is carried out between a portable code emitter ( 15 ) and a base station ( 1 ) for access to a motor vehicle. Both signals are correlated with each other and the dialogue repeated at an altered carrier frequency. The distance of the code emitter ( 15 ) from the base station ( 11 ) is determined from the difference in two phase difference measurements between the sent and received signal in one station ( 11 or 15 ). Access to, or use of the motor vehicle ( 10 ) is only permitted when the code emitter ( 15 ) is within a certain distance from the motor vehicle ( 10 ).