Exploiting Pseudorandom Sequences to Enhance Noise Immunity for Air-Coupled Ultrasonic Nondestructive Testing

The application of a pulse-compression procedure based on pseudorandom m-sequences to air-coupled ultrasonic nondestructive testing is presented. The signal-to-noise ratio enhancement assured by this technique is theoretically analyzed and experimentally verified, particularly focusing on the positive effect of the procedure to reduce quantization noise. The possibility of faithfully reconstructing signals whose amplitudes are lower than the quantization step of the analog-to-digital converter (ADC) board is analyzed theoretically and experimentally verified.