LARGE ANTENNA SYSTEMS,
Abstract
Large antennas are of importance in radar, communications, and radio astronomy applications where sensitivity and/or angular resolutions are important. However, several major limitations exist to the achievement of large size antennas. Among the limitations are mechanical and environmental factors, measurement limitations, spatial bandwidth, and the effects of random errors. Mechanical factors seem to limit the tolerance achievable in present practical antennas to about one part in 10,000 more or less. This tolerance results in an antenna size of less than 400 wavelengths, corresponding to beamwidths of about 1/6 degree. Larger antennas are possible, but usually with degraded performance. Many of the limitations due to the environment can be overcome by operation inside a radome, although the radome itself will impose a limit on the antenna size. Several common antenna types can be constructed in large sizes. The parabolic reflector in one of its many forms is the most common example of large antennas, whether movable or fixed. Array antennas with low gain elements are expensive in large sizes because of the large number of elements that they must contain. However, arraying of a modest number of large directive antennas is an attractive method for achieving large aperture and is widely employed by the radio astronomer. Aperture synthesis as practiced by the radio astonomer and synthetic aperture as employed by the radar engineer are methods for achieving the effect of a large antenna by time-sharing an aperture of modest or small size. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 29, 1967
- Accession Number
- AD0664462
Entities
People
- Merrill I. Skolnik
Organizations
- United States Naval Research Laboratory