Nonuniformly optimally spaced array with specified zeros in the radiation pattern

摘要

The object of this invention is to provide a method for a new nonuniformly spaced array with nonuniform amplitudes for sonar, seismic and electromagnetic applications, where the optimum positions and the optimum amplitudes of the array elements along its axis are systematically determined in order to produce a radiation pattern with specified zeros (nulls) in the radiation pattern. By specifying the zeros (nulls) of the radiation pattern one controls the beamwidth and the side- lobe level of a directive pattern, and certain other characteristics of other radiation patterns. This method is based on the present invention by which the radiation pattern of a nonuniformly spaced array with nonuniform amplitudes is expressed rigorously by a determinant, where the specified zeros (nulls) of the radiation pattern are introduced explicitly in the determinant in a simple form. Additional zeros (nulls) in the radiation pattern can be introduced implicitly by solving simultaneous equations for the coefficients in the developed determinants. This new invention applies in general to nonsymmetric nonuniformly spaced arrays with nonuniform amplitudes and with any number of elements either even or odd, where (N-1) zeros (nulls) could be specified explicitly for an array of N elements. This invention applies as well after a slight modification to the cases of symmetric nonuniformly spaced arrays with even or odd number of elements. For the particular case of uniformly spaced arrays with nonuniform amplitudes this new invention reduces to the classical polynomial array invented by S. A. Schelkunoff in 1943. This new array will be designated the Nonuniformly Optimally Spaced Array with Specified Zeros, or in short, the NOSA-SZ array.