Accession Number:

AD0735661

Title:

Limited Electronic Scanning with a Near-Field Cassegrainian System

Descriptive Note:

Technical rept.

Corporate Author:

MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB

Personal Author(s):

• Fitzgerald, William D.

Report Date:

1971-09-24

Pagination or Media Count:

28.0

Abstract:

The scanning characteristics of a near-field Cassegrainian antenna excited with a relatively small planar array are investigated theoretically and experimentally. The analysis uses both geometrical optics and scalar diffraction theory. The technique is a viable approach to the problem of modifying an existing high-resolution dish radar for limited scan capability. Feed requirements can be satisfied by virtually any planar array concept, i.e., phase scanning, frequency scanning, multiple-beam-forming networks, etc. The scan range is roughly approximated by a fixed angular field of view hence, the number of beamwidths scanned with electrically large apertures can be very high. Further, the system is free from the coma lobes usually associated with off-axis beams from a paraboloid. Design curves are presented from which one can determine the secondary characteristics - gain, scan loss, sidelobes, etc. - for a given arrayreflector configuration.

Descriptors:

• *PHASED ARRAYS
• SCANNING
• MATHEMATICAL ANALYSIS
• ANTENNA FEEDS
• PARABOLIC ANTENNAS

Subject Categories:

• Electrical and Electronic Equipment

Distribution Statement:

APPROVED FOR PUBLIC RELEASE