Broadband Analysis of Holographic Power Combining Circuits

Holography is a promising technique for power combining applications in the frequency range of short millimeter and submillimeter waves. In this paper, quasi-optical holographic power combining circuits are investigated. An equivalent network is utilized which rigorously models horn arrays and biperiodic dielectric structures in order to design computer-generated holograms. We apply the network model to a 5-element quasi-optical power combiner and demonstrate its capability. The hologram is designed for 150 GHz and has an efficiency of 92.5 % with a 90 % bandwidth of 5.3 %. With the aid of a broadband waveguide power divider and a vector field measurement system, the circuit is analyzed.     

Quantitative weight of evidence method for combining predictions of quantitative structure-activity relationship models

ABSTRACT

A method for combining statistical-based QSAR predictions of two or more binary classification models is presented. It was assumed that all models were independent. This facilitated the combination of positive and negative predictions using a quantitative weight of evidence (qWoE) procedure based on Bayesian statistics and the additivity of the logarithms of the likelihood ratios. Previous studies combined more than one prediction but used arbitrary strengths for positive and negative predictions. In our approach, the combined models were validated by determining the sensitivity and specificity values, which are performance metrics that are a point of departure for obtaining values that measure the weight of evidence of positive and negative predictions. The developed method was experimentally applied in the prediction of Ames mutagenicity. The method achieved a similar accuracy to that of the experimental Ames test for this endpoint when the overall prediction was determined using a combination of the individual predictions of more than one model. Calculating the qWoE value would reduce the requirement for expert knowledge and decrease the subjectivity of the prediction. This method could be applied to other endpoints such as developmental toxicity and skin sensitisation with binary classification models.     

行波光电二极管级联阵列输出功率合成研究

针对未来光载无线通信所需的高功率、大带宽的光电探测器,提出了一种行波光电二极管级联阵列功率合成电路.先将行波光电二极管级联,再按照阵列式结构将多组级联的光电二极管组合起来,实现射频功率合成,以获得高功率、大带宽的射频信号.采用EDA工具,对该光电转换射频功率合成电路进行仿真模拟.仿真结果表明,该功率合成电路可以有效地将各光电二极管的射频输出信号进行功率合成,功率合成后的信号带宽显著增加,仿真结果与理论分析完全一致.此外,电路分析表明,增加该功率合成电路中的高阻微带线的特性阻抗可以有效提高其输出射频信号的带宽.     

Single frequency lasing using coherent combining

We show that by coherently combining several solid state lasers it is possible to obtain a single frequency output. This is experimentally demonstrated by coherently combining four Nd:YAG lasers channels, each with a properly chosen cavity length, in order to suppress unwanted longitudinal modes and obtain a single frequency output. We also present a model that accurately predicts and supports out experimental results.     

光纤放大器阵列的远场特性研究

从光纤激光器阵列相干合成远场光强分布的解析表达式出发，详细研究了阵列占空比、阵元个数以及阵元的相位误差对相干合成远场图样分布、中心主瓣的角宽度及所占能量的影响. 给出了占空比为12.5%时，三路保偏光纤放大器相干合成的实验结果. 关键词： 光纤激光器阵列 相干合成 相位     

全光纤激光相干合成光谱响应特性研究

基于N-腔镜谐振腔理论对全光纤激光相干合成进行了理论分析，数值模拟了迈克尔逊型相干合成激光器的光谱特性，对两个光纤Bragg光栅的中心波长差和两路光的光程差对合成光谱特性的影响给出了理论解释.用啁啾光纤光栅取代其中一个光纤Bragg光栅，使激光相干合成的带宽由0.3 nm拓展到1.0 nm.     

若干经济数学模型的研究与应用

本文论述了近些年我们在投入产出模型、广告最优随机控制模型、最佳营销管理模型以及时间序列—马尔可夫链组合预测模型等方面所做的研究工作，同时也论及国内外在上述几方面的研究状况．     

Long-exposure far-field properties of the array of mutually-injected fiber lasers

In this paper, the long-exposure far-field properties of the array of mutually-injected fiber lasers are studied to understand the effect of the multiple phase-locked states on coherent beam combining of the array. It is found that the long-exposure far-field will degenerate into the superposition of the intensities of the elementary lasers when all the phase-locked states of the array are exported with the same probability. It means that the interference pattern will be greatly weakened in the long-exposure far-field because of the export of multiple phase-locked states of the array. This result implies that the multiple phase-locked states of the array go against coherent beam combining of the array, and only some of these phase-locked states should be exported. Then, the effects of the high-order phase-locked states on the far-field are discussed. The result suggests that only the in-phase state should be exported (i.e., all the other phase-locked states should be suppressed) in order to realize high-efficiency (> 80%) coherent beam combining when the number of the elementary lasers of the array is smaller than 19.     

用于抛物柱面空间功率合成天线的功分喇叭阵列

 提出了一种用于偏馈抛物柱面反射天线的功分喇叭。由于改善了口面上的电磁分布,该功分喇叭可以让馈源阵列的栅瓣电平抑制到－28 dB。用FEKO进行仿真发现,与传统用角锥喇叭阵列作为馈源的抛物柱面反射天线相比,使用功分喇叭直线阵列可以使空间功率合成天线的效率从68%提高到80%,同时天线的增益也能增加0.7 dB。     

Performance of two-hop infrastructure based multi-antenna regenerative relaying in Rayleigh fading channel

Cooperative relaying is considered as an effective technique to enlarge the coverage area and enhance the system capacity for the future wireless systems. In this paper, an infrastructure based multi-antenna cooperative relay network has been investigated. Closed form expressions of outage probability and average error rate have been derived, when the relay and the destination perform selection combining of the signals. The relay is assumed to operate in the adaptive decode and forward mode. The effect of number of antennas installed on the relay and their placement has also been studied.