Near field to far field DF antenna array calibration technique
AssigneeBAE Systems Information and Electronic Systems Integration Inc.
InventorKeith A. Struckman
Life of this patent
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Abstract
A technique is disclosed for calculating the phase and amplitude weighting factors for use with a specific compact antenna range that synthesize an in phase, constant amplitude planar wave front that appears to have been transmitted from the far field. The weighting factors are used to weight RF signals after they are received by a full size or scaled radio direction finding array mounted on a platform during testing of the antenna array on the compact antenna range. The weighted received signals accurately replicate the antenna array response in the far field, including electromagnetic glint caused by the platform on which the antennas are mounted, and are stored in complex voltage form as a calibration table for the array.
Claims20
A method for improving directional measurements made using a direction finding antenna array and receiver where weighting factors are first calculated for a compact antenna range, then a full scale or scaled model of the antenna array is placed on a test table of the compact antenna range and receives radio frequency test signals transmitted by a test probe antenna of the antenna range to develop a calibration table that is later used with the full scale direction finding antenna array in actual use to make more accurate direction finding measurements, said method comprising the steps of:
- calculating weighting factors defining in phase, constant amplitude, planar wave fronts impinging on the test table at a plurality of specific angles of incidence;
- performing the weighting factor calculations for each specific angle of incidence by taking into consideration a plurality of different angles of incidence surrounding each specific angle of incidence to emulate an in phase, constant amplitude planar wave front that is optimized over the area of the test table for each specific angle of incidence;
- and
- transforming the test signals received by the direction finding antenna array on the test table using the weighting factors and storing the transformed signals in the calibration table to be used in actual use to make more accurate direction finding measurements.
A system for calculating weighting factors for use with a compact antenna range that has a test table, the weighting factors being used to adjust phase and/or amplitude of radio frequency test signals radiated from a test probe antenna of the range, and the compact antenna range is used for testing a direction finding antenna array and a platform on which it is mounted that are placed on a test table of the antenna range to develop a calibration table that is later used with the direction finding antenna array and platform to make accurate direction finding measurements, said system comprising:
- means for calculating weighting factors defining in phase, constant amplitude, planar wave fronts impinging on the test table at a plurality of specific angles of incidence;
- means for performing the weighting factor calculations for each specific angle of incidence by taking into consideration a plurality of different angles of incidence surrounding each specific angle of incidence to emulate an in phase, constant amplitude planar wave front that is optimized over the area of the test table for each specific angle of incidence;
- and
- means for transforming the test signals received by the direction finding antenna array on the test table using the calculated weighting factors and storing the transformed test signals in the calibration table to be used in actual use to make more accurate direction finding measurements.
Dependencies are inferred from the claim text.