The thesis describes a method of' beam steering aimed at
producing a useful amount of deflection of an antenna beam
from boresight, by a simple and Inexpensive method. For
large antennas, It is difficult, as well as expensive, to
steer the beam by more than a few beamwidths. The method
studied was developed with particular reference to the
beam steering requirements of Direct Broadcast Satellite
flat plate antennas.
The method involves two dielectric wedges, having circular
faces, placed In front of the antenna. By adjusting the
relative angular position of the wedges, the beam can be
steered In any direction, up to a maximum value from the
antenna boresight direction. The maximum value of the
deflection is determined by the wedge angle and the
dielectric constant of the wedge material. This method of
beam steering Is Independent of frequency. Frequency
limitations are, however, set by the need for a matching
layer on the wedge faces to reduce the loss due to
reflection and also due to interference of multiple
reflection effects on the radiation pattern.
Extensive investigations are made (both theoretical and
experimental) to predict the performance of the wedges as
the beam Is steered. The effect of reflection is studied and a new matching technique is devised. Other practical
considerations for example, stepping the wedges for weight
reduction, the effect of loss in the dielectric material
and cross polar performance are also taken into account.
Some effort is given to explore the possibility of using
metal loaded artificial dielectrics using polyurethane as
the base material.
Finally, a number of charts are presented to determine the
amount of beam steering for an arbitrary position of the
wedges