Radar System Engineering

SEC. 16.18] THE SUPERSONIC DELAY LINE 667
16.18. The Supersonic Delay Line.—The principal elements of a
delay line are the transmission medium and the electromechanical transducers.
Because of the bandwidth required, MTI delay lines have been
FIG. 16.31.—Circuit of a balanced detector,
operated with amplitude-modulated carrier frequencies in the region of
15 Me/see. The transducers consist of piezoelectric quartz, X-cut and
optically polished. The two transmission media so far used are mercury
FIG. 16.32.—A supersonic mercury delay line of variable length.
and fused quart z. The principal factors encountered in line design have
been treated in detail elsewhere’ and will be briefly reviewed here.
Liquid Lines.—The simplest delay line is a straight tube with parallel
transducers at the end. A laboratory design of mercury line has been
shown in Fig. 16.10. A model for field use is shown k Fig. 16.32. The
1Chap 6, Vol. 17; Chap 24, Vol. 19, Chaps.13, 14, Vol. 20.