Analyses of pattern function of the DBF in non-uniform subarrays and a modified weighting method

The characteristics of the pattern function of a DBF (digital beamformer) composed of subarrays are analysed and a condition for the formation of grating lobes is given. For the design of a DBF, some conventional weighting methods, e.g., Hamming weighting, cosine-squared weighting and cosine-cubed weighting, are only suitable for a uniform array directly composed of array elements. We modify these methods to let them be self-adaptable, that is, suitable for a variety of arrays including the DBF in non-uniform subarrays. The principle of this new method is to modify weighted coefficients according to the relative positions of subarrays in the array. Both the analyses and the computer simulation results demonstrate that this method is rather effective.