Patent ID: 11945402
Assignee: ROBERT BOSCH (AUSTRALIA) PTY. LTD.
Field: Control (Instruments)
Classification: CPC B  H  G | IPC B  H

Claim 6:
7. A system for detecting if a relay is present in a passive entry passive start (PEPS) system for a vehicle, comprising:
antennas associated with the vehicle and a key fob using an low frequency (LF) receiver to measure LF signal levels; and
at least one controller configured to perform the following:
(a) transmitting from one or more antennas associated with a vehicle, a first and second LF signal and determine a minimum time gap between the first LF signal and the second LF signal such that the minimum time gap exceeds a channel coherence time of a high frequency wireless relay;
(b) determining a maximum time gap between the first LF signal and the second LF signal allowable by a timing requirement associated with the PEPS system of the vehicle and a maximum allowable change in position of a key fob;
(c) determining the time gap between the minimum time gap obtained at step (a) and the maximum time gap obtained at step (b) wherein if the minimum time gap from step (a) is greater than the maximum time gap from step (b), a system timing requirement from step (b) is increased to provide a predetermined time gap;
(d) separately transmitting, at the predetermined time gap from step (c) between the first LF signal and the second LF signal, the signals having a known signal ratio, from an antenna associated with a vehicle to a key fob as part of an LF challenge;
(e) measuring, at the key fob, signal levels of the first LF signal and the second LF signal; and
(f) determining if a ratio of the first LF signal and the second LF signal is within a predefined range.