Radiation Pattern Synthesis of the Coupled Almost Periodic Antenna Arrays Using Artificial Neural Network ANN Model

This paper proposes a radiation pattern synthesis of the almost periodic antenna arrays including mutual coupling effects (that extracted by the Floquet analysis according to our previous work), which principally has a high directivity and large bandwidth. For modeling the given structures, the moment method combined with the Generalized Equivalent Circuit (MoM-GEC) is proposed. The artificial neural network (ANN) as a powerful computational model has been successfully applied to the antenna array pattern synthesis. The results showed that the multilayer feedforward neural networks are rugged and can successfully and efficiently resolve various distinctive complex almost periodic antenna patterns (with different source amplitudes) (in particular, both periodic and randomly aperiodic structures are taken into account). However, the artificial neural network (ANN) is capable of quickly producing the synthesis results using generalization with the early stopping (ES) method. A significant time gain and memory consumption are achieved by using this given method to improve the generalization (called early stopping). To justify this work, several examples are developed and discussed.

Generating a 3D optical needle array with prescribed characteristics

Unlike the general optical needle along the optical axis, we propose a method to generate a three-dimensional (3D) array formed by optical needles with prescribed length and polarization direction. Moreover, the geometric model of the created array can be specified. With the aid of antenna array pattern synthesis theory and time reversal technology, a virtual uniform line source (ULS) antenna array arranged regularly near the confocal region of two high numerical apertures objectives is employed to obtain the required illumination in the pupil plane for creating the desired focal fields. Numerical results demonstrate that there is a one-to-one correspondence between the focal field and the virtual ULS antenna array elements. The length and polarization direction of the optical needles depends on the length and spatial direction of the virtual ULS antenna. The peculiarities of the focal field array, such as the polarization, length, number, spatial position and array structure, can be customized according to application requirements. The created optical needle array can be used for such application as 3D synchronous particle acceleration and manipulation, 3D parallel fabrication.

Array Pattern Synthesis Using a Hybrid Differential Evolution and Analytic Algorithm

In this paper, a hybrid differential evolution and weight total least squares method (HDE-WTLSM) is proposed for antenna array pattern synthesis. A variable diagonal weight matrix is introduced in total least squares method. Then, the weight matrix is optimized by differential evolution (DE) algorithm to control the differences of the desired level and the obtained level in different directions. This algorithm combines the advantages of evolutionary algorithm and numerical algorithm, so it has a wider application range and faster convergence speed. To compare HDE-WTLSM with DE algorithm and typical numerical algorithms, these methods are applied to a linear antenna array and a conformal truncated conical array. Using our method, lower sidelobe levels and deeper nulls are obtained. The simulation results verify the validity and efficiently of HDE-WTLSM.

Radiation Pattern Synthesis and Mutual Coupling Compensation in Spherical Conformal Array Antennas

This paper presents a novel technique based on Hybrid Spatial Distance Reduction Algorithm (HSDRA), to compensate the effects of deformity and mutual coupling occurred due to surface change in conformal arrays. This antenna surface deformation shifts the position of null points and loss of the main beam resulting in reduced antenna gain along with substantial undesirable effects on the antenna performance. The proposed algorithm, which cumulatively incorporates the Linearly Constraint Least Square Optimization (LCLSO) and Quadratically Constraint Least Square Optimization (QCLSO) techniques, is formulated to minimize/reduce the absolute distance between the actual (simulated/measured) radiation pattern and the desired radiation pattern while keeping the direction of main beam and nulls position under control. In particular, a 4x4 conformal microstrip phased array from planar surface is deformed to prescribe spherical-shape surface with various radii of curvature, is validated. For the enhancement of Gain of the conformal array antenna, Gain Maximization Algorithm is also proposed, the simulated results of which is compared to the traditional Phase compensation technique and unconstraint least squares optimization. The analytical results for both planar and spherical deformed configurations are first evaluated in MATLAB and then validated through Computer Simulation Technology (CST).