Patent ID: 6965296

Claim:
An access control and usage control device for a motor vehicle, comprising: a transmitting and receiving unit disposed in the motor vehicle, which can send and receive signals; and a portable code generator, which includes a receiver and a transmitter, with which the signals can be received and transmitted, wherein the transmitting and receiving unit is connected to multiple antennas spatially distributed in the motor vehicle, through each of which interrogation signals can be transmitted, the receiver of the portable code generator includes multiple reception antennas, with which the interrogation signals are received, wherein the reception antennas are connected to a field intensity measuring device, in which directions of field vectors are determined on the basis of measured field intensities of the received signals, the portable code generator includes a signal delay measuring device, which determines a signal delay difference or a phase difference between the interrogation signals, and the portable code generator includes an evaluation unit which determines a position of the portable code generator in relation to the motor vehicle on the basis of the directions of the field vectors and either the signal delay difference or the phase difference.