Phased-Array Calibration by Adaptive Nulling
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
Pagination or Media Count:
The limitations to ultra-low sidelobe performance are explored using a 32-element linear array, operating at L-band, containing transmitreceive T R modules with 12-bit attenuators and 12-bit phase shifters. With conventional far-field calibrations, the average sidelobe level of the array was about -40dB. In theory, considerably lower sidelobe performance is expected from such an array. Initially, sidelobe performance was thought to be limited by inadequate calibrations. An examinations of individual array element patterns showed a mirror symmetric ripple which could only be attributed to edge effects in a small array. Simulations indicated that more precise calibrations would not compensate for these element-pattern differences. An adaptive calibration technique was developed which iteratively adjusted the attenuator and phaser commands to create nulls in the antenna pattern in the direction of the nulls of a theoretical antenna pattern. With adaptive calibrations, the average sidelobe level can be lowered to -60 dB. The technique can be used for interference suppression by implementing antenna patterns with deep nulls in specified directions.
- Electrical and Electronic Equipment
- Solid State Physics