A MATRIX-FED CIRCULAR ARRAY FOR CONTINUOUS SCANNING.
NAVAL RESEARCH LAB WASHINGTON D C
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If the radiators of a circular array are connected to the outputs of a Butler matrix, a focused radiation pattern can be formed by establishing the proper current distribution on the inputs of the Butler matrix. Further, if the amplitudes of the input currents are held fixed, the pattern can be scanned through 360 degrees in azimuth by the operation of phase shifters alone, just as the pattern of a linear array is scanned by varying the phases of the element currents. One explanation of this is based on the assumption that the pattern can be written as the sum of a finite number of uniform pattern modes and that the relative phases and amplitudes of these modes can be adjusted to form a narrow beam. Then the beam is scanned by adjusting the currents feeding the Butler matrix. This is only qualitatively correct the patterns calculated from the actual current distribution established on the array by the matrix differ from the patterns formed from the ideal modes. There is reasonable agreement between the calculated patterns and those obtained experimentally with a 32-element array of dipoles used to demonstrate how a beam could be formed and then scanned. The inputs to the Butler matrix required to achieve a prescribed cophasal sector distribution on the array are determined from the synthesis procedure of Davies with the corresponding changes in the current distribution on the array for other beam positions. Author
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