OVERVIEW

Our discussion of instrumentation systems will be cursory at best, because this book emphasizes the electromagnetic features of the signals to be measured, not the means by which they are recorded. Despite our general treatment of instrumentation, however, the reader is provided with enough specific information to make judgments about design issues. Our discussion begins with the simple CW (continuous wave) instrumentation system, which was once popular because of its low cost, and which was at one time the only kind of radar operated indoors. Its low cost came at a high operational price, however: its stability was often measured in minutes, and it was therefore very frustrating to operate.

While the CW radar relies on cancellation to separate the desired target echo from other, undesired echoes, the pulsed radar relies on the relative timing of the received signals to achieve essentially the same objective. Because the pulsed radar was the basis of many effective tactical systems fielded during World War II, and because its design was relatively straightforward, it became the workhorse of the outdoor RCS test range, and remains so today. However, the outdoor pulsed radar, more likely than not, is now a coherent system, the consequence of the development of the phase-locked frequency synthesizer.

The contemporary trend, in fact, is the exploitatiom of the scattering-matrix radar, a coherent system that outputs no fewer than eight channels of information for every pair of transmitted pulses, and often double that. The complexity and timing of these systems is...