OPTIMISATION OF WIDE-BAND BEAM PATTERNS BY MEANS OF A JOINED SYNTHESIS OF WEIGHTING COEFFICIENTS AND PULSE ENVELOPE

摘要

Wide-band signals used in active beamforming offer some advantages compared to narrow-band ones: essentially, they improve range resolution, increasing in this way the image's definition. A great deal of work has already been done in the optimising of weighting windows which work under narrow-band conditions: unfortunately the results obtained are not well-suited to wide-band working linear arrays. Moreover, under wide-band conditions, the beam pattern profile depends not only on the weighting window, but also on the adopted pulse envelope. This paper describes the basic procedures and the results of a joined optimisation that acts on both the weighting coefficients and the pulse envelope at the same time. The developed optimisation algorithm is a stochastic procedure that relates the problem's variables to the molecules of a cooling substance, and an appropriate cost function to the energy of the substance. Although the proposed approach is quite general, here the optimisation algorithm is applied to linear arrays used in far-field. Finally one of the configurations of weighting window and pulse envelope resulting from the joined optimisation is shown, as well as its relative beam pattern compared to more traditional ones.