Radar System Engineering

SEC.6.6] PLANE DIL5’PLA YS INVOLVING ELEVATION 171
Range is always plotted vertically, and at short range the resolution
in angle is far greater than that afforded by the PPI. This
display, called “type B,” (shown in Figs. 6“7 and 68) is used in
situations where the chief considerations are the range and bearing
of point targets or groups of targets, with little or no importance
attached to the shapes of extended targets or the relative locations
of widely separated targets. It is especially useful in homing, and
in telling plots of range and bearing for recording elsewhere in polar
form.
2. Displays in which the desired angular field of view is so sinall that
the distortion can be made negligible by proper normalization of
(u) 150-milesweep, normal PPI with grid (b) 100-milesweep,B-scan,zerodelay.
squares.
FIG. 6.S.—Distortion causedby D-scopedisplay.
the range and angle scales. Such a display, known as a micro-D,
is simply a substitute for a PPI sector; it is used either because it is
technically easier to attain, or because the same indicator is alternat
ely used for a regular type B display. Proper normalization
requires that the angular dispersion be kept proportional to the
range to the center of the display.
The vertical analogue of the type B display, known as “type E,” will
be described in the next section.
6.6. Plane Displays Involving Elevation.-One rarely desires to know
the elevation angle or altitude of an aircraft target without also requiring
its range and bearing. Simultaneous azimuth and elevation information
can be obtained by two-dimensional scanning with a single antenna, by
the V-beam principle (Sec. 6“12), or by the use of separate radar systems
scanning respectively in azimuth and in elevation. In the last case, the