碳纤维复合材料在天线上的应用

本文叙述了碳纤维复合材料在天线上的应用情况，具体阐述了碳纤维复合材料天线结构形式及制作天线过程中的材料选择，铺层设计，表面金属化等问题。     

V形缝隙天线的研究

本文利用第二类尖劈并矢格林函数对任意夹角的Ｖ形缝隙天线进行了矩量法计算。Ｖ形缝开在Ｖ形金属板上，并且由双线从中间馈电。文中给出了缝隙口面场分布和天线Ｈ面方向图的理论计算结果和实验结果，两者基本吻合。文中最后给出了三种非Ｖ形弯曲缝隙的实验结果。     

地球站天线性能的入网要求及其发展趋势

本文系统总结了地球站天线ＩＮＴＥＬＳＡＴＭ网的最新技术要求，阐述了地球站天线指标的发展趋势，指出了现代卫星通信地球站天线设计研究的方向。     

矩形微带天线谐振频率的粒子群神经网络建模

谐振频率是微带天线设计过程中最重要的一个参数,直接决定设计的成败.文章提出一种改进的前向神经网络模型,该模型采用粒子群优化算法进行训练,网络结构可以根据被建模问题的复杂程度进行自适应调整,进而得到泛化能力好的神经网络.通过这种改进的粒子神经网络对矩形微带天线的谐振频率进行建模,得到的结果明显优于该问题已有文献的结果,可见这种粒子群神经网络对此问题的有效性.基于粒子群神经网络的矩形微带天线谐振频率模型可以明显提高微带天线的计算机辅助设计水平.     

一种 1x2x4分布式空时编码异步协作方案

协作分集技术可以有效提高移动通信系统的容量和可靠性。近年来,分布式空时码（DSTC）被广泛应用到协作分集系统以实现空间分集增益。然而,时间异步和频率异步会使正交DSTC的码字结构受到破坏,严重影响系统性能。本文针对时间异步的协作通信系统,提出一种基于分布式Alamouti STBC的1x2x4异步协作方案。对这种方案进行了理论分析和算法推导,并且重新定义了中继节点归一化后的发射信号幅度。仿真结果表明该方案的误比特率性能具有明显优势,能在时间异步的协作通信系统中很好地发挥多天线接收性能。     

阻容加载偶极天线的宽带性能及效率分析

从工程应用出发,提出同时具有分布电阻,集中电容以及同时具有集中电阻、电容这两种加载偶极天线理论分析模型,推导了对应的电流积分方程,并用分级正弦伽略金方法进行数值计算。给出了天线电流分布,输入阻抗,方向图及效率的计算结果,并与纯分布电阻加载天线进行了比较。分析表明,所讨论两种模式阻容加载天线的效率较分布电阻加载天线高,但其宽带性下降了。     

基于部分校准极化敏感阵列的信号DOA和极化参数迭代估计

针对安装于飞机机翼上,具有不同结构极化敏感天线的部分校准阵列,该文提出了一种完全极化电磁波DOA和极化参数的迭代估计方法。该方法基于部分校准阵列,估计阵列误差;然后利用阵列误差,估计单个极化敏感天线的极化导向矢量;最后利用极化导向矢量,估计完全极化电磁波DOA和极化参数。迭代运行上述三步,可以逐步提高估计精度。计算机仿真验证了该方法是收敛的,并且具有良好的鲁棒性。     

有耗半空间天线问题中的广义索末菲积分

本文给出了利用Ｐｒｏｎｙ法计算广义索末菲积分的详细过程；计算了近地水平电偶极子的近区辐射场。通过计算发现，只要逼近路径和调节参量选择得当，Ｐｒｏｎｙ法所得结果与数值积分法的结果十分吻合，完全可以放弃优化过程。     

Dielectric space frame radomes for satellite communications

The cross-polarization, signal attenuation and boresight shift for a number of dielectric space frame (DSF) radomes have been investigated using the induced field ratio method. It is shown that DSF radomes produce substantially less cross-polarization than their metal counterparts. It is concluded that in view of INTELSAT's specification of 30.7 dB cross-polar discrimination within an antenna's tracking beamwidth for frequency re-use communication system antennas, DSF radomes, in particular those considered, would not yield appreciable system degradation. The general method presented is extendable to other radomes structures provided that connectivity information is available.     

Microstrip antenna on a high dielectric constant substrate: BaTiO3 (BTO)-CaCu3Ti4O12(CCTO) composite screen-printed thick films

The performance of microstrip antennas using composite thick films of (BTO-BaTiO₃) and CCTO (CaCu₃Ti₄O₁₂) as a substrate were studied. The dielectric permittivity and loss of (BTO)_x-(CCTO)_1−x thick films with x=0, 0.2, 0.5, 0.8, 0.9, and 1 were examined. These films were prepared in two-layer geometry using the screen-printing technique on Al₂O₃ substrates. Mechanical alloying followed by the solid-state procedure was successfully employed to produce powders of CCTO (CaCu₃Ti₄O₁₂) used in the films. We also studied the films dielectric permittivity (K) and loss (D) in the medium-frequency (MF) range (100 Hz to 1 MHz). The performance of a planar microstrip antenna that uses the (BTO)_x:(CCTO)_1−x thick films as a substrate of high K was also examined in the microwave range of frequencies. From the analysis of the antenna operation of the samples, one can conclude that the higher values of K in the range of 2.5–3.3 GHz antennas is presented by the BTO substrates. For the BTO film, the K value is ∼66 (2.6 GHz) and decreases to 34 for the CCTO film (3 GHz). For the BTO and CCTO films, the antenna bandwidths (BW) are ∼50% and ∼38%, respectively. The higher bandwidth presented by the BTO compared to the CCTO is certainly associated with the higher loss presented by the BTO phase, which is a ferroelectric phase. Therefore, these measurements confirm the potential use of such materials for small microwave planar antennas, where the miniaturization of the devices is crucial.