Limited scan antenna array

Claim 2

A planar phase-steerable antenna array having an axis perpendicular to the array and having a main lobe whose direction is steerable by phase control over a region extending from the axis to an outer limit ranging from 0* to 25* off the axis comprising a phase-controlled energy feed system, element antennas arranged substantially in a plane with uniform spacing in a spacing range between 0.75 to 1.10 wavelength, each of said element antennas comprising feed terminals for accepting excitation energy from the feed system, means having a feedterminal end and a second end for conducting of said excitation energy from the feed terminals in a direction substantially parallel to the axis, a substantially planar main reflector nearer to the feed-terminal end of the conduction means than to the second end and parallel to the array plane for reflecting electromagnetic waves, a subreflector located at the second end of the conduction means and at a distance from the main reflector in a range of distances of 0.4 to 0.6 wavelength for reflecting electromagnetic waves, said subreflector having overall size parallel to the array in a range of 0.25 to 0.60 wavelength, electromagnetic radiation means connected to the conduction means between the main reflector and the subreflector and excited by energy conducted by the conduction means thereto for producing electromagnetic fields, the precise dimensions for said uniform spacing of the element antennas and for said distance of the subreflector from the main reflector and for said over-all size of the subreflector parallel to the array being chosen so as to provide an element-in-array pattern having a level that is uniform within + OR - 0.5 decibel everywhere within + OR - 15* of the direction of the main lobe and having a sidelobe level at least 18 decibels below the main lobe level everywhere beyond + OR - 85* from the direction of the main lobe.

Claim 3

A planar phase-steerable antenna array having an axis perpendicular to the array and having a main lobe whose direction is steerable by phase control over a region extending from the axis to an outer limit ranging from 0* to 25* off the axis comprising a phase-controlled energy feed system, element antennas arranged substantially in a plane with uniform spacing in a spacing range between 0.75 to 1.10 wavelength, each of said element antennas comprising feed terminals for accepting excitation energy from the feed system, means having a feed-terminal end and a second end for conducting of said excitation energy from the feed terminals in a direction substantially parallel to the axis, a substantially planar main reflector nearer to the feed-terminal end of the conduction means than to the second end and parallel to the array plane for reflecting electromagnetic waves, a subreflector located at the second end of the conduction means and at a distance from the main reflector in a range of distances of 0.4 to 0.6 wavelength for reflecting electromagnetic waves, said subreflector having overall size parallel to the array in a range of 0.25 to 0.60 wavelength, electromagnetic radiation means connected to the conduction means between the main reflector and the subreflector and excited by energy conducted by the conduction means thereto for producing electromagnetic fields, the precise dimensions for said uniform spacing of the element antennas and for said distance of the subreflector from the main reflector and for said over-all size of the subreflector parallel to the array being chosen so as to provide an element-in-array pattern having a level that is uniform within + or - 0.5 decibel everywhere within + or - 15* of the direction of the main lobe and having a sidelobe level at least 18 decibels below the main lobe level everywhere beyond + or - 85* from the direction of the main lobe.

Claim 4

A planar phase-steerable antenna array having an axis perpendicular to the array and having a main lobe whose direction is steerable by phase control over a region extending from the axis to an outer limit ranging from 0* to 25* off the axis comprising a phase-controlled energy feed system, element antennas arranged substantially in a plane with uniform spacing in a spacing range between 0.75 to 1.10 wavelength, each of said element antennas comprising feed terminals for accepting excitation energy from the feed system, means having a feed-terminal end and a second end for conducting of said excitation energy from the feed terminals in a direction substantially parallel to the axis, a substantially planar main reflector nearer to the feed-terminal end of the conduction means than to the second end and parallel to the array plane for reflecting electromagnetic waves, a subreflector located at the second end of the conduction means and at a distance from the main reflector in a range of distances of 0.4 to 0.6 wavelength for reflecting electromagnetic waves, said subreflector having overall size parallel to the array in a range of 0.25 to 0.60 wavelength, electromagnetic radiation means connected to the conduction means between the main reflector and the subreflector and excited by energy conducted by the conduction means thereto for producing electromagnetic fields, the precise dimensions for said uniform spacing of the element antennas and for said distance of the subreflector from the main reflector and for said over-all size of the subreflector parallel to the array being chosen so as to provide an element-in-array pattern having a level that is uniform within + or - 0.5 decibel everywhere within + or - 15* of the direction of the main lobe and having a sidelobe level at least 18 decibels below the main lobe level everywhere beyond + or - 85* from the direction of the main lobe.

Claim 5

A planar phase-steerable antenna array as defined in claim 1 wherein said means for conduction comprises open-wire transmission line means extending from said terminals to said subreflector, and said main reflector comprises a conductive ground planE substantially continuous across the array, and said subreflector comprises a conductive plate, and said electromagnetic radiation means comprises half-wave dipole means connected approximately midway between the main reflector and the subreflector.

Claim 6

A planar phase-steerable antenna array as defined in claim 2 wherein said uniform spacing of the element antennas is approximately 0.85 wavelength, said distance of the subreflector from the main reflector is approximately 0.5 wavelength, and said conductive plate is a disk having a diameter of approximately 0.41 wavelength.

Claim 7

A planar phase-steerable antenna array as set forth in claim 4 wherein said element antennas are spaced apart about 0.85 wavelength, said main and partial reflectors are spaced apart about 0.5 wavelength, said electromagnetic radiation means interposed between the main and partial reflectors comprises a half wave dipole interposed approximately midway between each of said main and partial reflectors, and each of said partial reflectors comprises a disk having a diameter of about 0.41 wavelength, whereby the energy coupling among element antennas has values such that, for steering directions within said range of + or - 15*, the gain of the array is degraded by less than 1 decibel and the maximum sidelobe level for regions 85* and farther from the main beam is below -20 decibels referred to the main beam.

Claim 8

A planar phase-steerable antenna array having an axis, comprising a plurality of equally spaced element antennas in a plane, each of said element antennas comprising structural member means having at least one dimension for determining mutual energy coupling of the element antenna with others of said element antennas in the array, said dimension being proportioned to produce an element-in-array radiation pattern flattopped with + or - 0.5 decibel everywhere within + or - 15* of the axis of said element-in-array pattern, energizing means for feeding phase-controlled excitation power to said elements for radiating an electromagnetic beam steerable within an angle of at least + or - 15 from said axis, each of said element antennas cocmprises feed terminals for accepting excitation power from the energizing means, means having a feed-terminal end and a second end for conducting of said excitation power from the feed terminals in a direction substantially parallel to the axis, a substantially planar main reflector nearer to the feed-terminal end of the conduction means than to the second end and parallel to the array plane for reflecting electromagnetic waves, and wherein said structural member means comprises a subreflector located at the second end of tHe conduction means and at a distance from the main reflector in a range of distances of 0.4 to 0.6 wavelength for reflecting electromagnetic waves.

Claim 9

A planar phase-steerable antenna array having an axis, comprising a plurality of equally spaced element antennas in a plane, each of said element antennas comprising structural member means having at least one dimension for determining mutual energy coupling of the element antenna with others of said element antennas in the array, said dimension being proportioned to produce an element-in-array radiation pattern flattopped with + or - 0.5 decibel everywhere within + or - 15* of the axis of said element-in-array pattern, energizing means for feeding phase-controlled excitation power to said elements for radiating an electromagnetic beam steerable within an angle of at least + or - 15 from said axis, each of said element antennas cocmprises feed terminals for accepting excitation power from the energizing means, means having a feed-terminal end and a second end for conducting of said excitation power from the feed terminals in a direction substantially parallel to the axis, a substantially planar main reflector nearer to the feed-terminal end of the conduction means than to the second end and parallel to the array plane for reflecting electromagnetic waves, and wherein said structural member means comprises a subreflector located at the second end of tHe conduction means and at a distance from the main reflector in a range of distances of 0.4 to 0.6 wavelength for reflecting electromagnetic waves.

Claim 10

A planar phase-steerable antenna array having an axis, comprising a plurality of equally spaced element antennas in a plane, each of said element antennas comprising structural member means having at least one dimension for determining mutual energy coupling of the element antenna with others of said element antennas in the array, said dimension being proportioned to produce an element-in-array radiation pattern flat-topped within + or - 0.5 decibel everywhere within + or - 15* of the axis of said element-in-array pattern, energizing means for feeding phase-controlled excitation power to said elements for radiating an electromagnetic beam steerable within an angle of at least + or - 15 from said axis, each of said element antennas comprises feed terminals for accepting excitation power from the energizing means, means having a feed-terminal end and a second end for conducting of said excitation power from the feed terminals in a direction substantially parallel to the axis, a substnatially planar main reflector nearer to the feed-terminal end of the conduction means than to the second end and parallel to the array plane for reflecting electromagnetic waves, and wherein said structural member means comprises a subreflector located at the second end of the conduction means and at a distance from the main reflector in a range of distances of 0.4 to 0.6 wavelength for reflecting electromagnetic waves, said subreflector having over-all size parallel to the array in a range of 0.25 to 0.60 wavelength, electromagnetic radiation means connected to the conduction means between the main reflector and subreflector and excited by energy conducted by the conduction means thereto for producing electromagnetic fields.

Claim 11

A planar phase-steerable antenna array having an axis, comprising a plurality of equally spaced element antennas in a plane, each of said element antennas comprising structural member means having at least one dimension for determining mutual energy coupling of the element antenna with others of said element antennas in the array, said dimension being proportioned to produce an element-in-array radiation pattern flat-topped within + or - 0.5 decibel everywhere within + or - 15* of the axis of said element-in-array pattern, energizing means for feeding phase-controlled excitation power to said elements for radiating an electromagnetic beam steerable within an angle of at least + or - 15 from said axis, each of said element antennas comprises feed terminals for accepting excitation power from the energizing means, means having a feed-terminal end and a second end for conducting of said excitation power from the feed terminals in a direction substantially parallel to the axis, a substnatially planar main reflector nearer to the feed-terminal end of the conduction means than to the second end and parallel to the array plane for reflecting electromagnetic waves, and wherein said structural member means comprises a subreflector located at the second end of the conduction means and at a distance from the main reflector in a range of distances of 0.4 to 0.6 wavelength for reflecting electromagnetic waves, said subreflector having over-all size parallel to the array in a range of 0.25 to 0.60 wavelength, electromagnetic radiation means connected to the conduction means between the main reflector and subreflector and excited by energy conducted by the conduction means thereto for producing electromagnetic fields.

Claim 12

A planar phase-steerable antenna array as defined in claim 7 wherein said means for conduction comprises open-wire transmission line means extending from said terminals to said subreflector, and said main reflector comprises a conductive ground plane substantially continuous across the array, and said subreflector comprises a conductive plate, and said electromagnetic radiation means comprises half-wave dipole means connected approximately midway between the main reflector and the subreflector.

Claim 13

A planar phase-steerable antenna array as defined in claim 8 wherein said uniform spacing of the element antennas is approximately 0.85 wavelength, said distance of the subreflector from the main reflector is approximately 0.5 wavelength, and said conductive plate is a disk having a diameter of approximately 0.41 wavelength, said diameter being one of said dimensions for determining said mutual energy coupling.

Claim 16

The method as defined in claim 10 wherein said step of measuring Within an angular range comprises measuring within a range of at least + or - 15*, and wherein said step of adjusting comprises adjusting so as to obtain a pattern flat within + or - 0.5 decibel within said range.

Claim 17

The method as defined in claim 10 wherein said step of progressively varying in increments at least one of said dimensions comprises progressively varying said breadth of an element antenna measured parallel to the plane of the array.