TABLE OF CONTENTS Chapter 5 discusses the characteristics of targets and clutter, and the detection of targets in the presence of clutter. Section 6.5 discusses clutter levels, the requirements for clutter suppression, and the limits of clutter suppression in AEW radars.
Sections 6.5.1 and 6.5.2 address AEW clutter levels caused by the earth's surface. Broadly speaking, there are two sources of surface clutter: land and sea. These surfaces create unwanted echoes that are received via the antenna major lobe (main beam) and the sidelobes. Main-beam and sidelobe clutter affect AEW radars differently and are therefore separately discussed.
Clutter is generally of two types: distributed and discrete. Examples of discrete clutter sources include water towers, buildings, utility poles, floating debris, and sea-wave prominences. Depending on circumstances, discrete clutter can of course be either undesirable clutter or targets of interest. Distributed clutter results from such sources as forests, cultivated land, foliage, grass, small waves, and wind ripples. Generally speaking, discrete clutter sources are sprinkled more or less randomly throughout the distributed clutter.
The average value of distributed surface clutter can be determined from the equation ? c = ? A c, where ? is the average clutter RCS when normalized to surface area. A c is the area of a radar range-azimuth cell. Typically for AEW, A c will be between 10 5 and 10 6 square meters. For small grazing angles (long ranges), ?
