This paper proposes an improvement to the whale optimization algorithm (WOA), which is based on the Levy flight technique. The improvement allows improved whale optimization algorithm (IWOA) to have a good diversity of population, faster convergence and overcome premature. The test by using different benchmark functions is conducted to demonstrate the effectiveness of improvement on the algorithm performance. Finally, IWO algorithm is applied to optimize the problems of two-way pattern of MIMO radar system, involving the achievements of sidelobe reduction, deep null, and wide null at the prescribed directions. The obtained numerical results demonstrate that IWOA can not only efficiently fulfill the expected deep nulls and wide nulls at the prescribed directions, but also enable the peak sidelobe level to retain in the smaller level at the same time than several state-of-the-art algorithms.
Ultra-wideband synthetic aperture radar is interfered by ground clutter and artificial jamming. In many cases the target's scatter signal can be approximated as Linear Frequency Modulated signals. Time-frequency Distribution, such as Winger-Ville distribution, provides a direct and effective analysis method of the time-frequency structures of Linear Frequency Modulated signals. Meanwhile, the cross terms of the Winger-Ville distribution can be smoothed through the smoothed pseudo Winger-Ville distribution. Combine Hough transform the time-frequency concentration is improved and better precision of parameter estimation will be obtained. Target detecting and parameter estimation by the smoothed pseudo Winger-Ville distribution and Hough transform for frequency-modulated jamming are simulated in this paper. The method proved to be efficient for target detecting and parameter estimation of Ultra-wideband synthetic aperture radar.
In this paper, an S/C/Ku triple-band (TB) dual-polarization (DP) shared aperture array (SAA) with an approximate frequency ratio of 1 : 1.8 : 4.5 is proposed. An S/C dual-band dual-polarized (DBDP) perforated patch antenna is designed as a shared element, and the S-band array consists of S-band-working shared elements. The C-band array interlaces with C-band-working shared element and C-band cross-patches with phase compensation. The Ku band array consists of dual-polarization rectangular dielectric resonator antennas (DRAs) for its small section area and high design freedom. In order to ensure the symmetry of the structure, all the ports adopt a vertical welding structure. A 1 × 3 prototype array is fabricated and measured, showing that the S-, C-, and Ku-bands obtain the bandwidths of 2%, 2.1%, and 1.8%, respectively. The polarization isolation is better than 20 dB in all three bands, while the cross-polarization is lower than −20 dB. The proposed array has the advantages of low cost and high integration; moreover, the proposed array owns excellent potential for expansion to large aperture benefited from its symmetry.
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