Uses of Ultrasonics in Radio, Radar and Sonar Systems

A short historical review is given of the development of ultrasonics. Uses in the low-amplitude range are sonar systems, dispersive and nondispersive delay lines, ultrasonic inspectoscopes, and crystal and mechanical filters. In all of these applications, the very low internal friction of metals and fused silica provides very low losses, while the guided wave properties of various shaped transmission paths provide either dispersive or nondispersive transmission. The dispersive transmission is useful for FM radar systems which are not limited in power by breakdown of the system, while nondispersive delay lines have uses in MTI radar systems, in pulse decoding systems and in computers. The low dissipation and frequency stabilities inherent in quartz crystal vibrations have been used extensively in the production of very selective filters and in the control of oscillators. Ultrasonics and hypersonics (frequencies about 109 cycles) are useful tools for investigating liquid and solid-state reactions.