Abstract:
The widespread application of paraboloidal reflector
antennas in microwave communication, radar and radio astro
nomy has stimulated considerable interest in the develop
ment of physically small improved feed systems which will
have high directivity, low side lobes and a multiple beam
facility. This work comprises of a detailed theoretical and
experimental investigations into the radiation characteris
tics of some improved primary feeds, with greater directivity,
increased on-axis gain and low side lobes, for reflector
antennas. The development of this new feed system are based
on design of new type of horn antenna using the properties
of unsymmetrical radial surface wave.
A new type of radiating structure using the properties
of unsymmetrical radial surface wave suggested by Arora [10]
has been designed and electric and magnetic field components
were derived using electric Hertzian vector potential.
The field lines were also drawn inside the horn using the
derived field equations. The radiation characteristics of
the newly designed structure were also studied in the forward
direction as well as in space. Results obtained show that
the system will have pattern with greater directivity and
low side lobes as compared to conventional type of horn
antenna of the same dimensions. The effort were also
made to design an optimum horn antenna to give a maxi
mum on -axis gain.
The effect of placing dielectric sphere in the
vicinity of radiating surface wave horn aperture has
been investigated. Sphere loading is seen to narrow the
-3db beamwidth. The sphere loaded system also posses
greater on -axis gain, low side lobes and a variable
beam feed system.
Finally some suggestions are made for further work
in this field.
