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Radar System Engineering

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86 PROPERTIES OF RADAR TARGETS [SEC.311<br />

As we can see from Fig. 3.15, this group of scatterers will lie within a<br />

patch of surface of nearly rectangular shape, with its area approximately<br />

given by<br />

A = (Rci) (+cT sec O). (28)<br />

Here we have used<br />

R= R’–; AR, (29)<br />

which is the range to a point in the center of the “target<br />

shaded in Fig. 3“15.<br />

area,” the area<br />

Rain<br />

echo<br />

Without A14 plate<br />

sweep:<br />

33 small div/mi<br />

-<br />

With A/4<br />

plate<br />

sweep & gain same as<br />

above<br />

Without 2/4<br />

Land targets<br />

plate<br />

sweep: 9.5 small div/mi<br />

Rain visible only at close<br />

range<br />

-<br />

With A/4<br />

plate<br />

gain increased 6 db<br />

Broad pip at center<br />

is artificial signal<br />

FIG. 3.14.—A-scopeobservationsof rain and land targets.<br />

The radar equation was derived in Chap. 2 for the case of a discrete<br />

target with cross section O, Eq. (2 W). This equation, repeated here, is<br />

(30)

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