基于DOLPH—CHEBYSHEV均匀园阵方向图的合成算法

均匀园阵(UCAs)以其具有的许多优点,在很多场合都利用园阵而不用线阵。提出了一种期望信号在任意入射角度且保证最小副瓣电平的阵列方向图合成算法。该方法优点是计算效率高,适用于实时波束形成和波束指向应用等。新算法是基于均匀线阵(ULAs)DOLPH-CHEBYSHEV方法提出来的。计算机仿真结果证明了新算法的有效性和正确性。     

A Modified Residue-Calculus Technique for Solving a Class of Boundary Value Problems-Part II: Waveguide Phased Arrays, Modulated Surfaces, and Diffraction Gratings

The modified residue-calculus technique (MRCT) described in a companion paper may be combined with scattering matrix, multiple-reflection techniques to provide solutions in scattering matrix form to thick-wall waveguide phased array, modulated surface, and strip grating geometries. Each of these geometries may be regarded as a periodic array of thin plates modified by dielectric fillings, waveguide steps, and terminations. Solutions to the modified geometries are found by combining the exact solution to the thin-wall array problem with approximate solutions to certain waveguide discontinuity problems found by the MRCT. In particular, a value of the dominant mode reflection coefficient versus scan angle for the thick-wall array may be found accurate to two or three significant figures without need for matrix inversion. In general, reduction of matrix size by a factor of 5 or more over conventional methods with equivalent accuracy may be realized.     

Design of Broadband Planar Arrays Based on the Optimization of Aperiodic Tilings

Antenna arrays based on aperiodic tilings have been shown to exhibit low sidelobe levels and modest bandwidths over which grating lobes are suppressed. In addition, compared to conventional periodic arrays, these arrays are naturally thinned (i.e., mean inter element spacing is greater than ). The generation of these arrays involves placing array elements at the locations of the vertices of an aperiodic tiling. To obtain a realizable design, the entire array is then scaled and truncated to achieve a desired minimum element spacing and aperture size. This paper demonstrates that it is possible to greatly extend the bandwidth of these arrays by incorporating a simple perturbation scheme into the basic array generation process. The implementation of this perturbation scheme is straightforward and it lends itself well to being combined with an optimization technique such as the genetic algorithm. It is successfully used to generate arrays that have large bandwidths (peak sidelobe level dB with no grating lobes) of up to a minimum element spacing of . Moreover, the flexibility of this technique will be further demonstrated by introducing a slight variation of the basic scheme that is capable of generating arrays with extremely wide bandwidths. An example will be presented for an array design that has a bandwidth corresponding to a minimum element spacing of up to .     

基于谐波分析的两阵元时间调制阵列测向方法

提出了一种利用时间调制阵列分析入射信号谐波特性的测向方法,针对传统的测向系统较为复杂,信号处理计算量大的问题,文中方法采用两个天线阵元和两个单刀单掷开关,在计算过程中使用了离散傅里叶变换减小了信号处理的计算量,数值仿真验证了该方法的有效性,且具有较好的测向精度。     

Comprehensive Approach to Modeling and Simulation of Photovoltaic Arrays

This paper proposes a method of modeling and simulation of photovoltaic arrays. The main objective is to find the parameters of the nonlinear I-V equation by adjusting the curve at three points: open circuit, maximum power, and short circuit. Given these three points, which are provided by all commercial array data sheets, the method finds the best I-V equation for the single-diode photovoltaic (PV) model including the effect of the series and parallel resistances, and warranties that the maximum power of the model matches with the maximum power of the real array. With the parameters of the adjusted I-V equation, one can build a PV circuit model with any circuit simulator by using basic math blocks. The modeling method and the proposed circuit model are useful for power electronics designers who need a simple, fast, accurate, and easy-to-use modeling method for using in simulations of PV systems. In the first pages, the reader will find a tutorial on PV devices and will understand the parameters that compose the single-diode PV model. The modeling method is then introduced and presented in details. The model is validated with experimental data of commercial PV arrays.     

Porous Polymer Coatings: a Versatile Approach to Superhydrophobic Surfaces

Here, a facile and inexpensive approach to superhydrophobic polymer coatings is presented. The method involves the in situ polymerization of common monomers in the presence of a porogenic solvent to afford superhydrophobic surfaces with the desired combination of micro‐ and nanoscale roughness. The method is applicable to a variety of substrates and is not limited to small areas or flat surfaces. The polymerized material can be ground into a superhydrophobic powder, which, once applied to a surface, renders it superhydrophobic. The morphology of the porous polymer structure can be efficiently controlled by composition of the polymerization mixture, while surface chemistry can be adjusted by photografting. Morphology control is used to reduce the globule size of the porous architecture from micro down to nanoscale thereby affording a transparent material. The influence of both surface chemistry as well as the length scale of surface roughness on the superhydrophobicity is discussed.     

“十”字环形缝隙阵频率选择表面的频率特性研究

本文用模匹配法分析了任意角度平面波入射时分析一般单元缝隙阵频率选择表面的频率响应性。这里考虑的ＦＳＳ是一零厚度无限大平面阵。问题的 解是以Ｆｌｏｑｕｅｔ 定理为基础。通过匹配ＦＳＳ表面的切向场分量获得的。     

Nature-Based Design of Aperiodic Linear Arrays with Broadband Elements Using a Combination of Rapid Neural-Network Estimation Techniques and Genetic Algorithms

The developments presented in this paper address the challenge of determining the optimal element positions in nonuniformly spaced broadband phased-array antennas in order to best meet desired performance criteria. Specifically, this is accomplished by introducing a new nature-based design technique that couples a robust genetic-algorithm (GA) optimizer with rapid neural-network (NN) estimation procedures. These provide performance criteria as functions of the element positions over the entire scanning range and bandwidth of operation. The objective of this GA-NN technique is to determine the optimal element positions for a broadband aperiodic linear phased-array antenna in order to minimize element VSWRs and sidelobe levels. The NN estimation procedures circumvent the need for computationally intensive full-wave numerical simulations during the optimization process, which would ordinarily render such an optimization task impractical. The effectiveness of the new GA-NN design synthesis technique is demonstrated by considering an example where a nonuniformly spaced linear phased array of ten stacked patch antennas is optimized for operation within a given bandwidth and scanning range.     

A New Approach to Computing Distortion of an FM Single-Tone Modulated Signal Due to Ideal Filtering

By factorizing a finite sum of harmonics, an expression is obtained for an FM demodulator output when the modulating signal is a simple sinusoid and the RF filter is an ideal bandpass filter. Using this result, harmonic distortions and the signal-to-distortion ratio are defined and computed; several curves are drawn to show the variation of these quantities in terms of the modulation index and the normalized bandwidth.     

A One-Pot Universal Approach to Fabricate Lubricant-Infused Slippery Surfaces on Solid Substrates

Wetting is a surface phenomenon that commonly occurs in nature and has an enormous influence on human life. Slippery liquid-infused porous surfaces have recently been developed to support the growing demand for anti-fouling coatings. While short-chain fluorinated compounds, commonly used to reduce the surface energy of substrates, are banned due to environmental toxicity, silane-based compounds are expensive and barely scalable. In this sense, silicone-based chemistry may match the gap as a real alternative. However, the grafting approaches demonstrated so far suffered from either slow binding kinetics or are applied under harsh conditions. Here, it is demonstrated that polydimethylsiloxanes graft to virtually any substrate when illuminated by UV light serving simultaneously as a reducing surface energy agent and infusing lubricant. This procedure is applied on metals, metal oxides, and ceramics of various surface morphologies. The proposed approach is simple, fast, scalable, environmentally friendly, and of low-cost, yet forms stable lubricant-infused slippery surfaces by a one-pot process. Due to the biocompatibility of silicone-based compounds, the process is examined on plain medically applicable substrates such as scalpel blades and glass lenses that display enhanced corrosion resistance, reduced friction through incision, and repel blood staining and bacterial adhesion without deteriorating their mechanical and optical characteristics.     

A HGGSA Approach to Beam Forming for DOA Estimation in Smart Antenna Arrays

Beam forming is one of the most important processes in smart antenna systems for DOA estimation. The most important function in beam forming is changing beam pattern of antenna for a particular angle. If the antenna does not change the position for the specified angle, the signal losses will be high. For avoiding this, a hybrid method, called HGGSA (hybrid genetic and gravity search algorithm) is proposed that is developed by combining genetic algorithm and GSA to beam forming for DOA estimation in smart antenna arrays. In the proposed method, if an angle is given as input, it will give the maximum signal gain in the beam pattern of the antenna with corresponding position and phase angle after searching through the space based on the HGGSA algorithm.

     

Study of Low Sidelobe Time Modulated Linear Antenna Arrays at Millimeter-Waves

In this paper, the time modulation technique for the design of low sidelobe antenna arrays is extended to millimeter-wave frequency band. Millimeter-wave rectangular waveguide is selected as the element radiators of linear antenna arrays, and the element radiation patterns are taken into account in the analysis and design of low sidelobe time modulated linear arrays. Two types of time modulation, namely, the time modulated variable aperture sizes (VAS) and unidirectional phase center motion (UPCM), are implemented in the design of low sidelobe millimeter waveguide linear arrays. It is observed that both the co-polarized and the cross-polarized components will experience the time modulation effect simultaneously. Many factors that affect the array performance are discussed.     

A Generalized Window Approach for Designing Transmultiplexers

This paper proposes a computational, very efficient, approach for designing a novel family of $M$ -channel maximally decimated nearly perfect-reconstruction cosine-modulated transmultiplexers. This approach is referred to as the generalized windowing method for transmultiplexers because after knowing the transmission channel a proper weighted sum of the inter-channel and inter-symbol interferences can be properly taken into account in the optimization of the window function, unlike in other existing windowing techniques. The proposed approach has also the following two advantages. First, independent of the number of subchannels and the common order of the subchannel filters, the number of unknowns is only four. Second, the overall optimization procedure is made considerably fast by estimating the above-mentioned sum in terms of two novel measures, namely, the signal to inter-symbol and the signal to inter-channel interferences, which are very easy to evaluate. Furthermore, when the transmission channel is not considered in the design, a table is provided, which contains the parameters for designing the prototype filter directly by using the windowing method without any time-consuming optimization. When comparing the resulting transmultiplexers with the corresponding perfect-reconstruction designs (the same number of subchannels and same prototype filter order), the levels of interferences are practically the same. However, when the system is affected by a strong narrowband interference, the proposed transmultiplexers outperform their PR counterparts. Design examples are included illustrating the efficiency of the proposed design approach over other existing techniques based on the use of the windowing method.      

Synthesis of Optimal Sum and Difference Patterns from Time Modulated Hexagonal Planar Arrays

An efficient array synthesis technique is developed for the design of optimal monopulse antennas in time modulated planar arrays with triangular lattices and hexagonal boundaries. Major emphasis is laid on the realization of low sidelobe array patterns from uniform amplitude excitations, and the inherent sideband radiations in time modulated arrays are suppressed to a sufficient low level. The synthesis technique implements the differential evolution strategy (DES) as the optimization tool, and a fast computation method based on 2D Fast Fourier Transform (FFT) is employed to speed up the optimization. Numerical results show that with the aid of the time modulation technique, the sum, difference, and double-difference patterns are obtainable from an array with fixed uniform amplitude excitations, thus demonstrating the effectiveness and validity of the proposed technique.     

一种有效的脉内调制信号识别方法

文章在相位重构的基础上分析了各种常见脉内调制信号相位差分序列的特征,并给出了它们的识别方法。采用多重相位差分改善了算法对低信噪比环境的适应能力。本文还根据分析给出了脉内识别的系统框图,最后仿真验证了文中分析结论,给出了不同信噪比下各种调制信号的正确识别率。     

一种基于多源信息的广义比例组合可靠性分配法

提出一种基于多源信息的广义比例组合电子系统可靠性分配法.该方法在GJB 299C-2006元器件失效率预计公式的基础上,按新研系统的新标准、新环境统一折合元器件失效率,估计相似单机失效率,而后按照新系统设计方案来组合各类型单机,最后利用余度系统比例组合法将系统可靠性指标分配至各单机.该方法拓展了比例组合法的适用范围.基...     

A Unifying Lattice-Based Approach for the Partitioning of Systolic Arrays via LPGS and LSGP

Various methods for the synthesis of systolic arrays from signal and image processing algorithms have been developed in the past few years. In this paper, we propose a technique for the partitioning problem, the problem to synthesize systolic arrays whose size does not match the problem size. Our technique generalizes most of the known lattice-based approaches to the partitioning problem and combines the multiprojection method for the synthesis of systolic arrays with the locally sequential-globally parallel (LSGP) and locally parallel-globally sequential (LPGS) partitioning schemes. Starting from (1) a k-dimensional large-size systolic array obtained from a system of n-dimensional uniform recurrences by a space-time transformation and (2) an arbitrary lattice in k-space inducing a partitioning of the array into subarrays, a small-size systolic array with a scalar-valued system clock is constructed via the LSGP or LPGS paradigm. In particular, the allocation function for the small-size array can be written in closed form and the timing function is obtained from timing functions for the subdomains, the set of operations performed by the subarrays, by simple greedy algorithms. In this way, the problem of finding optimal timing functions can in various cases be reduced to finding optimal timing functions for the subdomains. For problems of large size, these greedy algorithms seem to be preferable when compared with existing integer or non-convex programming formulations for finding (sub-)optimal timing functions. We also provide some new results, a necessary and sufficient condition for the existence of counter data flow, a formal relationship between partitionings of processor space and index space of the uniform recurrences in terms of counter data flow, and the structural equivalence between the lattice-based LSGP and LPGS schemes applied to the partitioning of index and processor space.     

圆柱面上的轴向偶极子阵的低副瓣方向图优化综合

本文利用新的非线性最优化方法讨论圆柱面上的轴向偶极子阵的低副瓣方向图优化综合问题，利用阵列的单元可实现增益方向图，我们把阵列综合问题表述为一个约束非线性规划问题，采用新直接法求解该问题即可得出一组使阵列的总方向图满足副瓣指标要求，同时具有尽可能高的方向性系数的激励系数，如果阵列的总方向图不能达到副瓣指标，则可得出一组使阵列方向图在可达到的副瓣方向图综合设计的模拟计算结果。     

空间扫描柱面轴向偶极子阵的低副瓣控制

本文利用约束非线性最优化方法，研究空间扫描柱面轴向偶极子阵的低副瓣综合问题。