Performance of thinning arrays by exponential spacings

The authors address the estimation of certain performance indices. The optimum designs considered for comparison are the dynamic programming technique introduced by M.I. Skolnik et al. (1964) (S-array), the sinuously perturbed spacing array by A. Ishimaru and Y.S. Chen (1965) (IC-array), and optimum arrays selected almost exhaustively by Y.T. Lo and S.W. Lee (1966) (LL-arrays). Two examples often seen in the literature are used. The region for comparison is restricted to the range mod u mod <1.947, since the S-array and the LL-array have a 0-dB gratelobe at mod u mod =2. The parameters and performances of various optimum arrays are listed. It is seen that the exponentially spaced array has nearly the same peak sidelobe level (PSL) as the LL-array for the array of nine elements if they have the same beamwidth (instead of length), and has the lowest PSL for the array of twenty-five elements if the beamwidths are equal. It is concluded that the exponential array is the best design in the sense of Dolph-Chebyshev for small- and medium-size thinning arrays (9>