1-14
The above formula is often written as:
For example, if a radar system has a pulse width of 5 microseconds, the range resolution is calculated
as follows:
In the above example, targets on the same bearing would have to be separated by more than 820
yards to show up as two targets on your indicator.
Bearing Resolution
Bearing, or azimuth, resolution is the ability of a radar system to separate objects at the same range
but at different bearings. The degree of bearing resolution depends on radar beam width and the range of
the targets. Range is a factor in bearing resolution because the radar beam spreads out as range increases.
A RADAR BEAM is defined in width in terms of HALF-POWER POINTS. All the points off the
centerline of the beam that are at one-half the power level at the center are plotted to define beam width.
When the half-power points are connected to the antenna by a curve, such as that shown in figure 1-11,
the resulting angular width of the curve is called the ANTENNA BEAM WIDTH. The physical size and
shape of the antenna determines beam width. Beam width can vary from about 1 degree up to 60 degrees.
In figure 1-11, only the target within the half-power points will reflect a useful echo. Two targets at the
same range must be separated by at least one beam width to be distinguished as two objects.
Figure 1-11.—Beam half-power points.
