Patent ID: 7701338

Claim:
An occupant detection system for detecting an occupant on a seat of a vehicle, the system comprising: an antenna electrode in a seat bottom of the seat, the antenna electrode including a proximity electrode constructed with a first electrode and a second electrode arranged adjacent to each other in the seat bottom; and an electronic unit connected to the antenna electrode and the vehicle, wherein the electronic unit applies a load current to the antenna electrode so as to generate a weak electric field, and detects a potential current passing through the antenna electrode, the electronic unit detects an occupant based on both of a first impedance and a first phase difference, and detects a conductive liquid included in the seat bottom based on both of a second impedance and a second phase difference, the first impedance, the first phase difference, the second impedance and the second phase difference are calculated based on the load current and the potential current, the first impedance is calculated to indicate an impedance between the seat bottom and a vehicle chassis of the vehicle connected to a ground, and the second impedance is calculated to indicate an impedance between the first electrode and the second electrode.