EXPERIMENTAL STUDY OF THE LOW FREQUENCY OPERATION OF A CASSEGRAINIAN ANTENNA
Abstract
The maximum allowable magnification factor of a conventional Cassegrainian antenna is shown to depend on the subreflector size in terms of wavelength. Use of excessively high magnification leads to inefficient operation, unless special precautions are taken. It is demonstrated experimentally that, for a given subreflector, satisfactory results can be obtained with a variety of feed horn sizes and locations, provided the subreflector can be defocused a distance of up to a few wavelengths. It is further shown that the subreflector shape is not critical if sufficient room is available for compensatory defocusing. Efficient operation is also possible without subreflector defocusing in a near-field configuration involving a large feed horn placed close to a subreflector having high magnification. The three- reflector system, which uses a small dish as the feed aperture, can be operated with little or no subreflector defocusing, but the system has low efficiency due to the low efficiency of the small dish.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 10, 1968
- Accession Number
- AD0686065
Entities
People
- Franklin I. Sheftman
Organizations
- Massachusetts Institute of Technology