Radar System Engineering

SEC,9.17] STABILIZATION OF THE BEAM 305
devise means of compensating for the angular motions of such vehicles,
and this mactice is known as stabilization.’ The techniaue falls into
two broad divisions, depending on whether the beam of radiation is
stabilized, or the data displayed on the indicator are stabilized or corrected
for the distortions caused by a tilting vehicle.
In general there is no choice between the two types of stabilization.
If the vehicle rolls or pitches to such an extent that its search radar no
longer scans the desired part of the field of view, beam stabilization is
necessary. This will prevent targets from fading from the indicator; if
they are then indicated, but at a false position, data stabilization becomes
a concurrent need. If the vehicle momentarily changes heading (yaws)
while on a certain course, the relative azimuth of targets will momentarily
ah er; the consequent aberration of the display can be, and has been, corrected
by either type of stabilization. Either sort of stabilization
requires the vehicle to carry gyroscopes or other devices which are sensitive
to direction in space and “know” the direction of north or up.
There are several ways of more or less completely mechanizing the
stabilization of the beam. The most obvious and perhaps the most
elegant is to provide a stable base for the scanner. This may be a platform
mounted on gimbals and controlled automatically to compensate
the pitching and rolling of the vehicle. If the vehicle rolls much but
pitches little, the pitch-gimbal axis may be omitted, and the stable-base
stabilization degenerates into roll stabilization.
A very different method of beam stabilization is possible in a scanner
having its main axis always perpendicular to the floor of the vehicle.
Use is made of the tilt axis of the antenna to the end that the antenna is
automatically directed toward the horizon, or to whatever angle above or
below the horizon is desired. The line of sight is thereby stabilized.
9.17. Stabilization of the Beam. Airborne Antenna Stabilization. 2—
Antenna stabilization for airborne radar is a scheme to preserve the same
conditions of radiation illumination in ponlevel flight as in level flight.
This is necessary to prevent (1) uneven illumination of the area being
scanned, (2) loss of radar range, or (3) distortion of the PPI presentation.
Stabilization equipment must be designed and constructed to stabilize
the beam of radiation, whether it be pencil or fan, against any maneuver
of the aircraft such as a climb, a glide, or any combination thereof. This
must be accomplished with components that are not affected by the
various accelerations, attitudes, or vibrations which might be encountered
in turns, climbs, glides, or banks.
A stabilizer may generally be broken down into three main components:
the gyroscope lvith its potentiometer or synchro take-offs, the
1‘~he theorv and Inethods of stabilization me discussedin Vol. 26 of this series
2By F. B. Lincoln.