Signal processing methods for improving the distance-resolution of the ultrasonic-pulse-echo-technique

The paper presents two signal processing methods which allow a separation of superimposed signals according to time and amplitude. It is shown, with regards to testing for defects near the upper surface, under which conditions the method can be used to separate upper surface-, rear wall-, and defect-echoes. It is reported that a chronological resolution and axial resolution of 0.7 wavelength of the ultrasonic frequency, and an amplitude resolution of 15 dB is attainable.