SOME OPTIMUM ANTENNA ARRAYS.
Abstract
This is a theoretical study of certain optimum linear arrays of nonuniformly spaced, isotropic antennas. For this purpose, the beamwidth of any given radiation pattern is defined in a new, integral sense, with low values denoting highly directional radiation patterns with low sidelobes. The present work is almost wholly concerned with the choice of (1) the excitation currents, and (2) the locations of individual antennas to minimize this particular beamwidth. It is shown that the first of these two choices reduces to a straightforward eigenvalue problem involving symmetric matrices. The search for the optimum element locations, however, requires also a knowledge of the derivatives of this 'best' beamwidth with respect to changes in the element spacings, together with some hunting procedure to arrive at configurations for which all those are zero. In the present computations, the latter consisted of a step-by-step procedure wherein the locally optimum beamwidth and its derivatives for any given array were first computed via the matrices, and successive neighboring configurations were then defined automatically with the elements shifted by amounts (of prescribed total magnitude) calculated to reduce the beamwidth as much as possible at every step. Numerical results of these computations are here presented for arrays ranging from four to forty symmetrically placed elements. On the whole, they seem to indicate that the best configurations in cases where the overall aperture is not constrained are ones in which the elements are spaced very nearly uniformly, with separations of the order of 0.8 to 0.9 times the wavelength. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1966
- Accession Number
- AD0648633
Entities
People
- Charles J. Drane Jr.
Organizations
- Air Force Cambridge Research Laboratories