Capacitive occupant detection system

A capacitive occupant detection system for a vehicle seat, comprising:

• an oscillator;
• a sensing electrode for being arranged underneath a surface of said vehicle seat,
• a shielding electrode, for being placed adjacent said sensing electrode so that said sensing electrode is situated between said surface and said shielding electrode, wherein said sensing and shielding electrodes are operatively coupled to said oscillator, wherein said oscillator is configured for driving said sensing and shielding electrodes with an oscillating voltage signal, said oscillating voltage signal being substantially the same in amplitude and phase for said sensing and shielding electrodes, a current being caused to flow in said sensing electrode in response to said oscillator driving said sensing and shielding electrodes, said current being responsive to an electric-field-influencing property of an object or occupant proximate to said electrode, said current occurring with a first current component in phase with said oscillating voltage signal and a second current component 90-degrees-phase-offset with respect to said oscillating voltage signal;
• a sensing circuit, operatively coupled to said sensing electrode and to said oscillator and configured for generating a first signal indicative of said first current component and a second signal indicative of said second current component;
• and
• a processor, operatively coupled to said sensing circuit, configured for determining an occupancy state based upon said first and second signals indicative of said first and second current components, respectively, and for outputting an output signal indicative of said occupancy state.

A capacitive occupant detection system, comprising:

• an oscillator;
• a transmitting electrode, operatively coupled to said oscillator, said oscillator being configured for applying an oscillating voltage signal to said transmitting electrode,
• a sensing electrode for being arranged in proximity of said transmitting electrode in such a way that a current may be caused to flow in said sensing electrode by capacitive coupling between said transmitting electrode and said sensing electrode, said current being responsive to an electric-field-influencing property of an object or occupant in a region between said transmitting and sensing electrodes, said current occurring with a first current component in phase with said applied oscillating voltage signal and a second current component 90-degrees-phase-offset with respect to said oscillating voltage signal;
• a sensing circuit, operatively coupled to said sensing electrode and to said oscillator and configured for generating a first signal indicative of said first current component and a second signal indicative of said second current component;
• and
• a processor, operatively coupled to said sensing circuit, configured for determining an occupancy state based upon said first and second signals indicative of said first and second current components, respectively, and for outputting an output signal indicative of said occupancy state.