Antitheft system for a motor vehicle
First Claim
1. An antitheft system, comprising:
- a stationary unit having a first oscillating circuit with an antenna;
a portable unit having a second oscillating circuit with a coil, and an energy accumulator connected to said second oscillating circuit; and
an oscillator oscillating with an oscillator frequency and having an output variable used as exciting variable with an exciting frequency for causing an oscillation of said first oscillating circuit, the exciting frequency changing for a first, predetermined period of time within a predetermined frequency range as soon as an energy supply of said stationary unit is switched on, to transmit energy signals inductively from said antenna to said coil, for at least partially charging said energy accumulator of said portable unit.
2 Assignments
0 Petitions
Accused Products
Abstract
An antitheft system for a motor vehicle includes a transponder having a charging capacitor which is wirelessly charged by energy signals from a transceiver. The level of the energy being transmitted depends on the quality of an inductive transmission between the transponder and the transceiver. Too little energy is transmitted if the exciting frequency of a transceiver oscillating circuit does not correspond to its resonant frequency due to component tolerances. In order to ensure that the charging capacitor is always quickly and properly charged, the exciting frequency is varied within a predetermined frequency range during a charging phase so that it passes in the vicinity of the resonant frequency at least once.
13 Citations
12 Claims
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1. An antitheft system, comprising:
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a stationary unit having a first oscillating circuit with an antenna; a portable unit having a second oscillating circuit with a coil, and an energy accumulator connected to said second oscillating circuit; and an oscillator oscillating with an oscillator frequency and having an output variable used as exciting variable with an exciting frequency for causing an oscillation of said first oscillating circuit, the exciting frequency changing for a first, predetermined period of time within a predetermined frequency range as soon as an energy supply of said stationary unit is switched on, to transmit energy signals inductively from said antenna to said coil, for at least partially charging said energy accumulator of said portable unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification