1.1 Definition of Radar

Radar is defined as a device for transmitting electromagnetic (EM) signals and receiving echoes from objects of interest (targets) within its volume of coverage [1]. Radar was originally an acronym for radio detection and ranging.

Many existing useful systems are described by that same definition, except that they utilize sound waves rather than EM waves. Such systems are typically called sonar (or, in some applications, ultrasound). By that definition, bats navigate using sonar rather than radar. Sonar principles are very similar to those of radar; however, sonar is beyond the scope of this book.

Unless otherwise specified, this book assumes that EM energy is transmitted from the radar hardware to an antenna, radiated from the antenna, scattered from one or more external objects, collected back at the transmitting antenna, and received by the radar hardware. Such a radar is called monostatic, that is, the transmitting and receiving locations are the same. Occasionally, reference is made to bistatic radars, in which the transmitting and receiving locations are different, or to multistatic radars, which involve transmission from one or more locations and reception at one or more locations. Radar is discussed in a number of books [2 16],

1.2 Brief History

The history of radar, especially the early history, is a fascinating subject in itself. Excellent treatises have been prepared by Budieri [17], Burns [18], Swords [19], and others. Briefly, the history of radar is as follows. In 1886, Heinrich ...