Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
2000-12-21
2003-01-14
Blum, Theodore M. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C343S771000
Reexamination Certificate
active
06507313
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to radar antennas, and particularly reflector radar antennas.
BACKGROUND OF THE INVENTION
The use of Flanking-beam Array Switching Technique (FAST) in combination with a phased array radar antenna is generally well known. Phased array antennas include multiple radiating elements, such as slots. These elements are typically configured in a planar construction and are individually controllable in phase and amplitude. U.S. Pat. No. 4,675,681, entitled “ROTATING PLANAR ARRAY ANTENNA”, issued Jun. 23, 1987 to Richard Kinsey (the '681 patent), teaches one such antenna. The entire disclosure of the '681 patent is hereby incorporated by reference herein.
FIG. 1A
illustrates one face of a dual face FAST (Flanking-beam Array Switching Technique) antenna system of the type for use, for example, on ships according to the '681 patent. The antenna
20
includes a pair of arrays
22
,
24
each having a plurality of waveguides
26
arranged in parallel fashion and extending generally horizontally. Each array is made up of a plurality of slotted waveguides, preferably made of rectangular, thin walled aluminum. The waveguides may be supported by a grid of vertical
28
and horizontal
30
rectangular structural tubes. The waveguides are mechanically fastened to the vertical tubes
28
which are supported by the horizontal tubes
30
. The horizontal tubes are mounted upon a dual A-frame structure
32
fabricated from structural aluminum I-beams. Each array is shown mounted in a tiltback angle of approximately 20 degrees relative to the vertical axis
34
of the support structure
32
. An azimuth motor
38
is mounted upon the support structure to drive the antenna in azimuthal rotation. Roll motors, one of which is shown at
40
, stabilize the antenna about the roll axis which is perpendicular to axis
34
, by controlling the ballscrew assembly
42
, using roll position signals provided from the ship's gyro repeater (not shown). A housing
43
provides environmental protection for the antenna components located at each end of each array. A radome
60
comprising a planar sheet of epoxy glass or a similar material resistant to weather damage and transparent to the RF signals transmitted by the antenna is attached to the aperture face.
FIG. 1B
illustrates a schematic view of a bi-directional FAST feed system suitable for use with the antenna of
FIG. 1A. A
pair of adjacent waveguides
100
,
102
are shown schematically as having slots
104
,
106
, respectively, offset by one-half the slot spacing. An excitation source
108
is connected to one end of each of the waveguides and coupled through phase shifters
110
,
112
to supply phase controlled power to each of the respective waveguides. The excitation source
108
is. also connected to hybrid load
118
. An excitation source
126
is coupled through phase shifters
128
,
130
to waveguides
100
,
102
, respectively, and is connected to hybrid load
132
.
Using the bi-directional feed, two beams
120
,
122
(
FIG. 1C
) can be formed simultaneously from one slotted waveguide
100
when excited using excitation source
108
. The excitation source
126
produces a pair of beams
134
,
136
(
FIG. 1C
) at the mirror image positions of the beams
120
,
122
produced by source
108
. Thus, as is illustrated in
FIG. 1C
, a total of four possible flanking beams for each array aperture are generated. Each of the beams can be electronically scanned in elevation by computer control of the phase shifters to provide surveillance of an area from 0 to 60 degrees or more in elevation with each rotation of the aperture.
There are known applications for radar antennas and systems which require relatively small and relatively low-cost packages. However, a realized drawback of a FAST antenna system is their relative bulkiness and undesirable high cost. Accordingly, it is an object of the present invention to provide a relatively low-cost and compact antenna system utilizing the FAST.
SUMMARY OF THE INVENTION
A radar tracking antenna system including: a parabolic-cylinder reflector; and, a subset of Flanking Beam Array Steered Technique (FAST) line feeds coupled to the reflector as a feed assembly.
REFERENCES:
patent: 4675681 (1987-06-01), Kinsey
patent: 4814779 (1989-03-01), Levine
patent: 5192954 (1993-03-01), Brockelsby et al.
patent: 5223846 (1993-06-01), Campbell
patent: 5805114 (1998-09-01), Podger
patent: 6111542 (2000-08-01), Day et al.
Blum Theodore M.
Duane Morris LLP
Lockheed Martin Corporation
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