Factors Affiecting the Performance of Linear Arrays

The performance of a linear array, which has been designed for low side-lobe level, is markedly affected by small variations in element excitation, introduced primarily, by the inaccuracies that are inherent in the manufacture of the array. Thus, the phase and amplitude of each element contain a slight randomness and the array performance must be determined by the application of statistical methods. This method of analysis has been formulated for the generalized symmetric linear array and computed for the special cases of three 24-element linear-shunt slot arrays usig a Dolph-Tchebyscheff current distribution. The statistics give the probability that the side-lobe level will exceed an arbitrary comparison value as a function of the magnitude of arbitrary manufacturing tolerances. The results indicate that the lower the design value of the sidelobe level the greater the perturbation to be expected for the allowed tolerance. Thus, an additional restriction is imposed upon array design which forces the designer either to require very small tolerances in manufacture or to overdesign the array in order to compensate for the perturbations introduced by the manufacturing processes.