Nonuniformly optimally spaced array with specified sidelobe positions 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 sidelobe positions (directions) in the radiation pattern. By specifying the sidelobe positions (directions) in the radiation pattern one controls the beamwidth and the sidelobe level value 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 symmetric nonuniformly spaced array with nonuniform amplitudes is expressed rigorously by a constant plus a determinant, where the specified sidelobe positions (directions) of the radiation pattern are introduced explicitly into the determinant in a simple form. Additional number of sidelobe positions (directions) in the radiation pattern may be found implicitly by solving a determinantal equation. The values of the sidelobe levels in the radiation pattern may be specified in relation to each other, and/or in relation to the value of the main beam level, and these relationships will be expressed by determinantal equations, to be solved directly, or through the application of related transcendental trigonometric equations or sets of equations, in order to obtain the optimum positions of the array elements along the axis of the array. This new invention applies in general to symmetric nonuniformly spaced arrays with nonuniform amplitudes and with either even or odd number of elements, where (N-1) sidelobe positions (directions) could be specified explicitly and independently in a simple form for a symmetric array with (2N) or (2N+1) elements. This new array will be designated the Nonuniformly Optimally Spaced Array with Specified Sidelobe Positions, or in short, the NOSA-SSLP array.