考虑馈源位置误差的面天线机电耦合优化设计

 针对面天线结构设计中存在的机电分离以及忽视馈源位置误差的问题,从机械电磁两场耦合的角度,将反射面天线主面误差和馈源位置误差统一到天线方向图的远场计算公式中,从而可以研究包含馈源支撑结构在内的天线结构参数对主要电性能（包括增益、副瓣、波瓣宽度、指向精度等）的影响。利用该公式建立了包含馈源支撑结构参数的天线整体机电耦合优化模型,通过某8米天线的仿真对比表明了该耦合优化模型的优点,最后将该优化模型应用于某40米大型反射面天线,取得了满意的效果。     

基于模型传递的平板裂缝天线复杂模型机电耦合仿真

天线结构受到外力作用会发生变形,直接影响天线的电性能,在电子产品机电耦合分析上,不同物理场间的数据传递是研究的重点和难点,文中提出了一种基于Hypermesh 的不同物理场间的数据传递方法。首先,利用APDL 语言获取并导出天线结构变形网格;然后,利用Hypermesh 重构实体方法,将网格生成实体,同时,通过一个悬臂梁验证了实体重构过程具有较高精度;最后,将重构模型导入电磁仿真软件中进行电性能的分析,该方法通过有限元仿真方法分析复杂天线模型的机电耦合问题,还考虑了各种耦合因素,以平板裂缝天线为例,通过实验验证了文中方法的正确性。     

反射面天线机电场耦合关系式及其应用

针对反射面天线随机误差和系统误差的特点,通过对Ruze公式、最佳吻合和提出的机电场耦合关系式的分析比较,从理论上研究了三者的差别.即Ruze公式未考虑反射面的系统误差,从而导致对天线结构设计和制造精度要求往往过高,而最佳吻合虽考虑了系统误差,但未考虑随机误差.机电场耦合关系式则将两种误差同时考虑进去了,并将电性能表示为...     

基于支持向量回归的腔体滤波器机电耦合建模与优化

为了提高装配后的滤波器电性能和成品率,该文提出了一种基于支持向量回归的腔体滤波器机电耦合建模和优化方法。该方法根据工程中积累的经验数据,首先应用改进的多核线性规划支持向量回归算法建立了制造精度对滤波器电性能影响的机电耦合模型,然后应用此模型优化了滤波器的制造精度,从而获得了最优的机械结构尺寸。实际滤波器的实验结果验证了该方法的有效性。该方法可用于批量生产的腔体滤波器的计算机辅助制造系统中。     

基于结构误差的六边形相控阵天线电性能分析

相控阵天线(Phased Array Antenna,PAA)阵面加工、安装中产生的随机误差导致天线电性能的下降,严重制约高性能PAA的发展.通过考虑互耦参数,且将阵面存在的结构误差作为附加的相位因子引入到天线方向图函数中,建立了平面六边形PAA阵面结构误差与天线电性能之间的结构-电磁耦合模型,并仿真分析了考虑互耦时结构误差与天线电性能的定量关系,以及天线阵元个数变化时,阵元安装精度和阵面平面度对天线电性能的影响规律,为工程设计人员帝定天线结构方案与制造公差提供了重要参考.     

面天线结构机电综合优化设计

运用天线机电耦合理论，对面天线结构进行机电综合优化设计。建立了以天线增益为目标的结构多工况优化模型，基于可行方向法，编制了具有一定通用性和工程实用价值的优化程序。优化过程中采用可视化监控、暂停和变量冻结的技术。对在自重载荷作用下的16m口径圆抛物面天线结构进行了优化设计，结果表明该优化程序收敛快、稳定性好。     

星载智能天线结构的机电热耦合优化分析

基于提高星载智能天线电性能和降低作动器能耗的目的,提出了一种以天线增益和作动器能耗为目标函数的结构、电磁、热耦合优化模型,其中约束条件包括杆件结构强度、作动器结构强度和作动器主动行程等,并把太阳热辐射作为初始外载荷.8m天线在六种不同工况下的耦合优化分析结果证明了该机电热耦合优化模型的有效性.     

大型空间桁架面天线的结构 —电磁耦合优化设计

 由于载荷变化及各种随机干扰,大型空间桁架面天线必须保持非常精确的形状.基于提高空间天线电磁性能以及降低作动器能耗的目的,结合大型空间桁架天线结构的特点,建立了以天线轴向增益和作动器能耗为目标函数,以结构强度、作动器变形和轴力为约束条件的多目标优化模型.数值试验结果表明,结构—电磁耦合优化设计模型只需较低的作动器能耗,就能明显提高天线电性能,很好地满足了天线结构与电磁设计要求.     

分布式MEMS移相器桥高度与相移量的机电集成模型及应用

移相器是控制相控阵天线空间波束捷变的方向盘,其性能的优良决定着相控阵天线性能的高低。微机电系统(MEMS)移相器优势明显,但由于相控阵天线工作环境复杂,环境载荷会导致MEMS移相器结构变形,进而直接降低整个相控阵天线的性能。为此,该文研究MEMS移相器关键结构参数和电性能之间的耦合关系,将复杂环境要素对物理结构的影响传递到结构参数和电参数上,推导出分布式MEMS移相器的机电集成模型,并利用集成模型对变形MEMS移相器进行电性能快速评估和结构公差计算。仿真结果说明了集成模型的有效性和工程应用价值。     

一种天线阵面精度补偿优化方法

大型天线阵面在机械载荷和温度载荷的综合作用下产生的变形,可以导致其电性能波动甚至失效;实际应用中,常采用补偿结构修正该变形以保证其性能。文中给出了一种阵面精度补偿方法:阵面工作前利用调整机构使天线阵面产生预变形,从而使天线阵正常工作时变形引起的增益损失最小化。通过建立天线阵机电热耦合有限元模型,构建优化数学模型计算调整机构最优调整量,并使调整量公差最大化,达到了改善天线阵电性能、减轻加工安装难度、降低制造成本的目的。     

表面纹理对反射面天线电性能的影响

反射面天线面板的加工质量包括加工精度和表面质量,两者都会影响天线的电性能。论文针对研究较少的表面加工质量,利用分形函数建立表面纹理的数学模型,并通过相位差将微观表面纹理引入天线的远场方向图计算公式,利用三角形单元的Gauss积分公式数值求解。通过仿真,分析了不同的表面纹理幅度、密度和粗糙程度对天线远场方向图的影响。研究发现:表面纹理的幅度越大,对方向图的影响越大;密度越大、越粗糙,影响越小。而且,幅度的影响最大,密度其次,粗糙程度影响最小。仿真的结果与模型定性分析的结论符合。所提出的模型和方法为研究面板表面加工质量对反射面天线电性能的影响提供了新的思路,得出的结论也可供工程实践参考。     

Nonlinear operation of a planar circular-grating DBR laser

An approximate method for the analysis of the nonlinear operation of a planar circular-grating distributed Bragg reflector laser is presented. The analysis is based upon vector-wave self-consistent coupled-mode equations modified to take into account gain saturation effects. With the help of an energy theorem and threshold field approximation, an approximate formula relating small-signal gain to the output power and laser parameters is derived. The laser characteristics obtained reveal behavior of the optimal coupling strength of the Bragg reflector, which provides maximal power efficiency as a function of the laser parameters. It is also shown that the gain saturation effect provides mode selectivity in the laser structure     

Pattern measurements of reflector antennas in the compact range andvalidation with computer code simulation

The measurements were performed at the University's compact range facility. They demonstrated: (1) the excellent dynamic range that can be achieved with antenna pattern measurements in a compact range facility; and (2) the excellent validation achieved for the calculated patterns of two 8-ft diameter reflector antennas. The compact range has a rolled edge modification to its reflector and uses a pulsed radar system to eliminate the clutter interference such that a dynamic range of more than 80 dB can be obtained. The measured far field patterns of two 8-ft reflector antennas, a prime focus fed antenna and a Cassegrain antenna, at 11 GHz were compared with those calculated by Ohio State University's Reflector Antenna Code. The computer code simulation's approach is also briefly described     

Stationary phase method for far-field computation of defocused reflector antennas

Computation of the far field of a defocused reflector antenna using the stationary phase method is described. The positions of the stationary phase points are determined, to eliminate one of the two numerical integrations of the radiation integral. Examples of scan patterns and computational time saving are presented.     

Equivalence of surface current and aperture field integrations for reflector antennas

The "extinction theorem" is used to prove that the fields of reflector antennas determined by integration of the current on the illuminated surface of the reflector are identical to the fields determined by aperture field integration with the Kottler-Franz formulas over any surfaceS_{a}that caps the reflector. As a corollary to this equivalence theorem, the fields predicted by integration of the physical optics (PO) surface currents and the Kottler-Franz integration of the geometrical optics (GO) aperture fields onS_{a}agree to within the locally plane-wave approximation inherent in PO and GO. Moreover, within the region of accuracy of the fields predicted by PO current or GO aperture field integration, the far fields predicted by the Kottler-Franz aperture integration are closely approximated by the far fields obtained from aperture integration of the tangential electric or magnetic field alone. In particular, discrepancies in symmetry between the far fields of offset reflector antennas obtained from PO current and GO aperture field integrations disappear when the aperture of integration is chosen to cap (or nearly cap) the reflector.     

G/T maximization of a paraboloidal reflector fed by a dipole-diskantenna with ring by using the multiple-reflection approach and themoment method

A 1.8-m paraboloidal reflector fed by a dipole-disk antenna with a beamforming ring is optimized for high G/T at L-band by using the moment method (MM) and the multiple reflection (MR) approach. The MR approach is based on using MM to calculate the radiation and scattering patterns of the feed, using physical optics plus uniform geometrical theory of diffraction (UTD) to include the reflector, and in addition to include the mutual interaction (multiple reflections) between the reflector and the feed by using the expression for the sum of an infinite geometric series. The MR approach is shown to be equally accurate as a MM solution of the complete antenna with reflector, provided the reflector is in the far field of the feed, and the MR approach is much faster. As a result of the calculations using the MR approach, design curves are presented showing how the G/T varies as a function of antenna geometry, size, and elevation angle, all for a given noise profile of the surrounding sky and ground. The computed radiation patterns and G/Ts are compared with measurements for several elevation angles and surrounding terrain     

Analytical method of pattern analysis for cluster-fed reflectors with random feed displacements

An innovative analytical method for the evaluation of the directivity patterns of cluster-fed reflector antennas with random feed element position and orientation displacements is presented. In this approach, the sensitivities of the incident magnetic field, far electrical field and directivity are derived with respect to the feed element position and orientation displacements. The effect of random position and orientation displacements on the directivity pattern is investigated via the numerical characteristics of the directivity with pre-calculated sensitivities; meanwhile, the upper and lower bounds of the directivity pattern are illustrated. A seven-element cluster-fed offset reflector is utilised as a numerical example to show the application of this method with different feed element position and orientation displacements. Comparison with the Monte Carlo method demonstrates the effectiveness and applicability of the proposed method.     

Decoupling Efficiency of a Wideband Vivaldi Focal Plane Array Feeding a Reflector Antenna

A focal plane array (FPA) feeding a reflector can be used to achieve a large field of view (FOV) with overlapping simultaneous beams. In order to provide a continuous FOV over more than an octave bandwidth, the inter-element spacing in the FPA has to be electrically small over large parts of the band. This will inevitably result in strong mutual coupling effects between the array elements. On transmit, the total lost power due to mutual coupling can be quantified by the decoupling efficiency, a term recently introduced for antenna arrays. This paper presents measured decoupling efficiencies of a Vivaldi element FPA operating between 2.3 and 7 GHz. The radiation patterns of the FPA are calculated for two beam excitations by using measured embedded element patterns, and the corresponding decoupling efficiencies are evaluated by using measured $S$ -parameters between all element ports. The FPA is assumed to illuminate a deep reflector with $F/D=0.35$ , and the overall reflector aperture efficiencies are computed. The decoupling efficiencies are also determined through the measurements of the total radiation efficiencies in a reverberation chamber, which includes material absorption losses.