An efficient density weighting approach for side-lobe level suppression of linear array antennas

Most likely, there axe two techniques existed to reduce the side lobe level (SLL) of array antennas: The conventional excitation amplitude tapering (AT) and the unusual element space density tapering (DT). The AT technique, such as triangular, cosine, cosine-square and raised-cosine amplitude distributions, as well as the Dolph-Chebyshev or Taylor current coefficients, provides efficient means for low SLL (LSLL) and ultra-low SLL (ULSLL) pattern synthesis, and also affords significant dynamic ranges control of the aperture distributions. The feed network, however, becomes complicated and narrow bandwidth, the aperture efficiency decreased rapidly as the amplitude getting much tapered. The DT technique offers another way for limited SLL reduction while the aperture efficiency is maintained, the antenna is a uniformly excited non-uniformly spaced array with element positions thinned from the center element (odd number array) or center two elements (even number array), the main advantage is that it simplifies the bulk and lossy feed network. In this paper, A uniformly excited symmetrical array antenna, which is compose of a uniform central sub-array (central part) and two density tapered side sub-arrays (side parts), is presented for SLL suppression, a power function characterized by two-parameter is employed to express the increments between adjacent elements of the two side parts, the optimum values of the two parameters are searched by the Min-max method according to the peak SLL. Numerical examples are given for the cosine-element, one half wavelength least spacing, and 4-element central part arrays, 8-, 10-, and 12-element arrays are simulated; Dolph-Chebysheve liked patterns are observed, -19.5dB, -20.8dB and -21.4dB SLLs are achieved, respectively.