Patent ID: 8219286

Claim:
A vehicle occupant detection system with noise reduction for reducing a noise signal coupled into the system, said noise signal characterized as having a series of harmonic frequencies based on a fundamental frequency, said system comprising: a controller configured to output an excitation signal having an excitation frequency value between harmonic frequencies; and an electrode arranged proximate to an expected location of an occupant for sensing an occupant presence proximate thereto, said electrode coupled to the controller and configured to output an electrode signal in response to the excitation signal, said electrode signal comprising the noise signal, said controller further configured to receive a series of electrode signal values based on the electrode signal and at a rate based on a sampling period, and to process each one of the electrode signal values prior to receiving a subsequent electrode signal value, wherein said sampling period is greater than a processing time for the controller to process one of the electrode signal values and has a varying phase difference with respect to the excitation signal, wherein to process each electrode signal value said controller is configured to execute a pre-determined algorithm; wherein to execute said pre-determined algorithm said controller is further configured to recall one or more stored filter coefficients that define a digital filter that reduces the noise signal by an effective amount, multiply each electrode signal value by one or more of the filter coefficients to form a corresponding one or more terms, and add each term to one of a plurality of output signal accumulators to calculate a series of filter output values, thereby filtering the electrode signal to reduce the noise signal.