Patent ID: 7692529
Filing Date: 2010-04-06
Classification: B60R,G07C

Abstract:
1. A passive entry and immobilizer key for vehicles, comprising: an integrated front-end circuit with three battery-supplied receiver channels each connected to an associated external antenna circuit including an inductor-capacitor combination having a resonant frequency in the very low frequency range, the antennas of the associated external antenna circuits being arranged in a three-dimensional configuration; and at least one immobilizer transponder supplied by energy received from an external transponder antenna circuit and stored in a storage capacitor, the transponder antenna circuit including an inductor-capacitor combination having a resonant frequency in the low frequency range, wherein the external transponder antenna circuit shares at least an inductive component with one of the associated external antenna circuits of one of the three receiver channels, a capacitor in the transponder antenna circuit being selectively disconnected to change the resonant frequency from a frequency in the very low frequency range to a frequency in the low frequency range.