Ultrasonic sensor system and method having input capture for echo processing

Abstract

An ultrasonic sensor system (36) has a transducer (40) that emits an ultrasonic signal (54), in response to an electrical excitation signal (52) from driver/receiver circuitry (42), and outputs an electrical response signal (58), in response to receipt of a reflected ultrasonic signal (56) from an object, such as a vehicle occupant (14). The response signal (58) is an oscillating signal that has a voltage amplitude indicative of the strength of the reflected ultrasonic signal (56). A receiver circuit (68) of driver/receiver circuitry (42) processes the response signal (58) from said transducer (40) and outputs an analog, non-oscillating signal (60). The analog signal (60) has a voltage amplitude indicative of the voltage of the electrical response signal (58). A comparator (84) of a comparator preprocessor (44) compares the voltage of the analog signal (60) to a predetermined reference voltage (VREF1) and outputs a digital signal (38). The digital signal (38) is indicative of whether the voltage of the analog signal (60) is greater or less than the reference voltage. A controller (28) processes the digital signal (38) for determining distance between the transducer (40) and the occupant (14). Preferably, the controller (28) controls a protection module (18).

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