Geometrical structures, stability, electronic properties, vibrational spectrum and polarizations of BeSi_n(n=1-12) clusters are investigated with density functional theory (DFT) at B3LYP/6-311G level. It indicates that there are many isomers with extremely close energies near the ground state. The most stable structures of BeSi_n clusters favor three-dimensional structures as n≥4. At n=1 spin multiplicity of the ground state structure of BeSi_n cluster is triplet while it is singlet as n≥2. Electronic properties of host clusters change obviously due to encapsulation of Be atom. Doping of Be atom reduce chemical stability of pure Si clusters, n=3, 5, 7 and 9 are magic numbers.

An efficient method is shown for radiation pattern of large plane arrays.Active element patterns of a large plane array are constructed from those of a small linear array.Field radiated by a large plane array is obtained by summing up active element pattern of all elements.With this method a large plane array analysis problem is converted into a small linear array problem,and thereby computational cost is considerably reduced.In addition,a hybrid method using extrapolative method combining with genetic algorithm is proposed for synthesizing desired patterns of large plane arrays.To assess accuracy and efficiency of the hybrid method,a low side lobe 10×10 plane microstrip patch antenna array is synthesized with the method.Calculated results agree well with that by HFSS.

An analytical formula for radiation field of dipole arrays based on equivalent circuit theory was verified in previous works.We extend this concept to field scattered by dipole arrays.Based on analytical formulas,a method is proposed to synthesize desired radiation and scattering patterns of dipole arrays simultaneously by optimizing element positions with PSO.To verify accuracy and effectiveness of the method,a linear dipole array is designed to obtain low side lobe level radiation and scattering patterns.Good agreement between results with the proposed method and FEKO validates accuracy of the method.Maximum sidelobe level of radiation and scattering patterns at operating frequency are both reduced by optimization.Furthermore,maximum levels of MRCS patterns in-band at threat angles are also considerably reduced.