Precision and Intelligence Lab., Tokyo Inst. of Technol., Nagatsuta 4259, Midori-Ku, Yokohama 227, Japan
A pulse signal has been utilized extensively for estimating travel time in an ultrasonic field. Travel time can be measured by calculating the time difference between transmitted signal and received signal. In a conventional method, time resolution is limited to its pulse width. Also, the received signal has an influence on the transducer characteristic and propagation characteristic and is distorted from the transmitted signal. It is not easy to compare between two different signals for measuring travel time. A technique to analyze the pulse signal by phase for measuring travel time is proposed. This technique can be applied to both a continuous-wave method and an impulse wave method for measuring travel time. The major feature is that the fluctuation of signals dependent on time is displayed in time domain, faithfully. Another feature is a method for identifying different amplitude signals, because this technique is independent of their amplitudes and dc bias. This technique is useful and acceptable for estimating time information such as travel time.