Improved Ultrasonic Sensitivity Using Pseudo-Random Binary-Code Phase-Modulated Signals

Abstract

Random signal systems are used in radars, but very seldom in medical and materials ultrasonic applications. Yet, compared with conventional techniques which use the same peak power, pseudo-random signal correlation techniques can easily improve the signal-to-noise ratio by a thousand or more times without sacrificing spatial resolution. To overcome the limitations imposed by the high ratio of peak power to average power, we developed a technique by which the echo energy is integrated with respect to time. As in radar systems, we used a sinusoidal signal which was phase-modulated by the pseudo-random binary code. This approach simplified our apparatus compared to those techniques using noise signals.