Signal processing for smart ultrasonic sensors

As typical smart sensors, ultrasonic sensors evaluate the information impressed on the propagating ultrasonic signal by the quantities to be sensed. Besides the ultrasonic transmission, reception, and time-dependent amplification, elementary signal processing includes time measurement, time-window evaluation, and phase detection. Flow velocities can be measured with high resolution and independently of the speed of sound using the lambda-locked loop (LLL). With echo profiles, advanced techniques such as object recognition by partial echoes are possible. These can be enhanced by deconvolution or inverse filtered transmission with respect to the normal echo of a plane surface. Similarly, objects and positions are recognized by using their echo profiles as the normal echo. For echo profiles from different positions (sensor in motion or in arrays), lateral structures are resolved by synthetic aperture or holography. The development of smart ultrasonic sensors will be stimulated by the future VLSI signal processor components. As examples of readily available smart ultrasonic sensors, a range of presence detectors and a heat meter with an LLL flow sensor are presented