TABLE OF CONTENTS Generally, few things are of more fundamental concern to both designer and user alike than the maximum range at which a radar can detect targets. In this chapter, we will learn what determines that range.
We will begin by tracking down the sources of the electrical background noise against which a target's echoes must ultimately be discerned and finding what can be done to minimize the noise. We will then trace the factors upon which the strength of the echoes depends and examine the detection process. Finally, we'll see how, by integrating the return from a great many transmitted pulses, a radar can pull the weak echoes of distant targets out of the noise.
Airborne radars can be designed to detect targets at ranges of thousands of miles. As a rule though, they are designed to operate at much shorter ranges for at least one compelling reason: obstructions in the line of sight.
Radio waves of the frequencies used by airborne radars behave very much as visible light, except of course that they can penetrate clouds and are not scattered much by aerosols (tiny particles suspended in the atmosphere). They cannot penetrate liquids or solids very far. And although they bend slightly as a result of the increase in the speed of light with altitude and spread to some extent around obstructions, these effects are slight.
Consequently, no matter how powerful a radar is or how ingenious its design, its range is essentially limited to...
