Radar System Engineering

120 LIMITATIONS OF PULSE RADAR [SEC.4.1
move in single file. It must be concluded that the restriction which
thus arises can be overcome only by the use of multiple channels. The
simplest—at least in conception—and the most direct way to do this is
to use two or more radar systems, apportioning to each a part of the
region to be covered.
This method is not the only practical scheme for multichannel
operation. In fact, in one of the most important existing applications of
multichannel operation, the “V-beam” radar, an increase in the amount
FIG. 4.1.—Principle of V-beam height measurement.
1. Plane of Beam I is vertical. Plane of Beam II falls back45°from Beam I. Ground
edgesof both beamsare common at K.
2. As both beamsrotate tozether, target T is pickedUPin Beam I whengroundedgesof
both beamsare at K. –
3. Target T is later picked up in Beam H when groundedges of both beams are at K’.
4, The angle formed by the advancement of the ground edges from K to K’ (Aq$)
dependson the angle Oof elevation of the target T.
of information provided is achieved in a more subtle and, under the
circumstances, a more effective way. The V-beam principle permits
a single scanning radar to give height as well as range and
azimuth of aircraft. In addition to the vertical fan beam which is characteristic
of microwave search radar (cf. Chap. 15), the V-beam set
provides an additional fan beam that is rotating at the same speed and
the plane of which is tilted out of the vertical. If the azimuth and range
of a target are known from the first beam, the height can be inferred
from the time of appearance of the same target in the second, or “slant”
beam (see Fig. 4.1). This latter beam is associated with a completely