Radar System Engineering

590 EXAMPLES OF RADAR SYSTEM DESIG.V [SEC. 152
factors, and the ingenuity of the development and design men was
taxed to meet the minimum acceptable radar performance within
these limits.
A detailed treatment of further systems beyond these two would be
of questionable value, since changing requirements may soon make
obsolete all but the more general, basic developments of the past. Radically
new requirements will be met only by radically new developments,
and to be firmly bound by past experience would stifle progress. Ingenious
technical men with good facilities, free in their thinking, working in
close touch with using organizations, fully informed on operational
problems and planning—these are the important requirements for future
advances.
15.2. The Need for System Testing. ‘—One general remark concerning
system design is sufficiently important to be made before taking up the
design examples. No radar system is complete until adequate provisions
for performance testing and maintenance have been made and appropriate
maintenance procedures prescribed.
The most important function of test equipment in radar maintenance
is to permit quantitative measurement of those properties of the system
which affect its range performance. Experience has shown that it is
essential to determine by reliable quantitative methods how well a radar is
operating. Under most circumstances, the important units of test
equipment should be built into the radar in a way that permits their most
convenient use. If limitations of weight and bulk do not permit the use
of built-in test equipment, suitable test points should be provided to
permit convenient and adequate tests to be performed frequently on the
important parts of the system.
Radar Performance Figure.—The ratio of P, the pulse power of the
radar transmitter, to Smin, the power of the minimum detectable signal,
is a measure of the radar performance. This is the fundamental quantity
studied in tests. The radar equation given as Eq. (2. M),
4 pnL4?f,
R ~,x . — (1)
d sm,ArA”
shows that all factors except P and tl~,n are either invariable or beyond
our control once the radar has been designed.
A quantity closely related to Smin is usually measured rather than
Sti~ itself. This maybe the power of the weakest test signal that can be
detected, or of a test signal that produces some other easily reproducible
effect. Because of the effects of presentation time and pulse width
~By R. D. O’Neal and J, M. Wolf.