Ultrasonic Echo Signal Feature Identification Using Lifting Scheme

To identify ultrasonic echo feature of hydraulic system ultrasonic non-intrusive measurement signal corrupted by noise, a new method to design wavelet according to the signal characteristic is developed. This method is based on lifting scheme, the initial set of finite biorthogonal filters is followed by lifting and dual lifting, and different lifting operators and dual lifting operators are obtained, and then new wavelet with particular properties is constructed. According to the noise characteristic at decomposition level, the de-noising threshold adaptively calculated. The ultrasonic signal is de-noised and recovered, and the ultrasonic characteristics in time domain are extracted. New constructed wavelet is applied in the signal de-noising of ultrasonic echo signal, ultrasonic echo wave crest and the time interval in time domain are desirably identified. The results confirm that new constructed wavelet outperforms the traditional wavelet method.