DIGITAL SIGNAL-PROCESSING TECHNIQUES FOR HIGH-ACCURACY ULTRASONIC RANGE MEASUREMENTS

The low bandwidth of current ultrasonic transducers for range measurements in air produces waveforms with relatively high rise and fall times. This is a cause of errors when echoes are detected by simple threshold-crossing techniques. To overcome this drawback, several digital signal-processing algorithms are considered, including L1, L2 norm, and correlation with different approaches for envelope extraction. The influence of different factors such as S/N ratio, sampling frequency, and digitizing resolution on measurement errors are analyzed using a synthetic approach through nearly 40 000 simulations. Results show different performance levels involving accuracy, computing time, and cost for the studied methods, although all of them allow us to reduce errors by several orders of magnitude.