Method of determining excitation of individual elements of a phase array antenna from near-field data
First Claim
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1. A method comprising the steps of:
- (a) selecting a set of at least first and second off-broadside beam directions for taking near-field data on a phased array antenna which is capable of steering its beam in multiple directions relative to the broadside direction of its array face;
(b) steering said antenna beam in said first direction and taking near-field amplitude and phase data at a selected RF frequency along a measurement grid;
(c) steering said antenna beam in said second direction and taking near-field amplitude and phase data at said selected RF frequency along said measurement grid;
(d) transforming to the far field said near-field data taken with said beam steered in said first direction to provide a set of first direction far-field data points;
(e) transforming to the far field said near-field data taken with said beam steering in said second direction to provide a set of second direction far-field data points;
(f) selecting a subset of said first direction far-field data points all of which are within visible space and a subset to said second direction far-field data points all of which are within visible space; and
(g) combining said subsets to represent a complete fundamental period of the array spectrum comprised of some first direction data points and some second direction data points each of which is within visible space in the far-field data set from which it is taken.
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Abstract
A near-field data measurement technique which provides sufficient data to enable the resolution of array element characteristics which are localized within a circle having a radius less than 0.61λ is disclosed. This allows phase correction of individual array elements having spacings substantially less than 0.61λ during the alignment of a phase array in a near-field test system.
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Citations
10 Claims
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1. A method comprising the steps of:
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(a) selecting a set of at least first and second off-broadside beam directions for taking near-field data on a phased array antenna which is capable of steering its beam in multiple directions relative to the broadside direction of its array face; (b) steering said antenna beam in said first direction and taking near-field amplitude and phase data at a selected RF frequency along a measurement grid; (c) steering said antenna beam in said second direction and taking near-field amplitude and phase data at said selected RF frequency along said measurement grid; (d) transforming to the far field said near-field data taken with said beam steered in said first direction to provide a set of first direction far-field data points; (e) transforming to the far field said near-field data taken with said beam steering in said second direction to provide a set of second direction far-field data points; (f) selecting a subset of said first direction far-field data points all of which are within visible space and a subset to said second direction far-field data points all of which are within visible space; and (g) combining said subsets to represent a complete fundamental period of the array spectrum comprised of some first direction data points and some second direction data points each of which is within visible space in the far-field data set from which it is taken. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. In a method of aligning a phased array antenna which is capable of steering its beam in multiple directions relative to the broadside direction of the array face in which (1) near-field data is taken, (2) that near field data is transformed to a far-field spectrum (3) that far-field spectrum is transformed to the aperture of the antenna to determine element excitations and (4) that antenna is aligned on the basis of those determined element excitations, the improvement comprising the steps of:
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(a) selecting a set of at least first and second off-broadside beam directions for taking said near-field alignment data; (b) steering said beam in said first direction and taking near-field amplitude and phase data at said selected RF frequency along a measurement surface; (c) steering said beam in said second direction and taking near-field amplitude and phase data at said selected RF frequency along said measurement surface; (d) transforming to the far field said near-field data taken with said beam steered in said first direction to provide a set of first direction far-field data points; (e) transforming to the far field said near-field data taken with said beam steered in said second direction to provide a set of second direction far-field data points; (f) selecting a subset of said first direction far-field data points all of which are within visible space and a subset of said second direction far-field data points all of which are within visible space; and (g) combining said subsets to represent a complete fundamental period of the array spectrum comprised of some first direction data points and some second direction data points each of which is within visible space in the far-field data set from which it is taken.
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Specification