TABLE OF CONTENTS In constructing a complete radar system, the designer must bear in mind not just the production of signals by the radar receiver, but the interpretation of those signals. Though radar is now put to many diverse uses, its original purpose of detecting objects in some volume of space still constitutes a major part of all its applications. In this case, the user is interested in distinguishing targets in the illuminated volume from the clutter and noise that tend to obscure it. Once a target has been detected, properties such as its range and velocity are likely to be of interest.
For a variety of reasons, the voltage supplied by the receiver is never steady, even if the receiving antenna is fixed. Thermal noise is one source of fluctuation for which there is no cure; the laws of physics are always with us. Other fluctuations may be due to variation within the illuminated volume of space, as can happen if a sidelobe of the main beam is illuminating the ocean or wind-blown vegetation. There may be random emitters contributing to the received signal, such as radio waves from space ( cosmic noise ). For a comparatively small part of the time, under most circumstances, part of the fluctuating signal will be due to the presence of targets.
By examining this fluctuating signal, the operator (human or machine) attempts to find events corresponding to objects of interest. The absence of events may also be important, as can occur when an apparent detection...
