一种用于突发通信的全数字解调器设计

本文介绍了一种应用在低速率短消息突发通信场合的全数字解调器.该解调器具有频率捕获范围宽(频偏可达几倍符号率),帧效率高(无需专门的同步码)等优点.文中给出了关键算法的仿真结果,最后给出了基于DSP的硬件设计.     

产己酸菌Lysinibacillus fusiformis SigA基因的克隆、表达及生物信息学分析

通过克隆产己酸菌Lysinibacillus fusiformis SigA全长基因,并对其进行表达和生物信息学分析。结果表明,SigA基因开放阅读框（ORF）有1 128个碱基,编码327个氨基酸,其分子质量为45.275 kDa;生物信息学预测表明,L. fusiformis与Lysinibacillus sphaericus具有较近的亲缘关系,二者序列相似度达97%;该蛋白为亲水性可溶性蛋白,与Bacillus sp. B14905相似度达100%,其二级结构主要由α-螺旋和loop环状构成,α-螺旋和loop环状分别占其二级结构的60.15%和 37.79%;预测并优化的三级结构由14个α-螺旋和15个loop构成。     

RBS ANALYSIS OF DAMAGE AND ANNEALING OF ION IMPLANTED InP:Fe

Rutherford backscattering spectroscopy (RBS) with channeling technique has been used to analyze the damage and its annealing of Si+ and P+ implanted InP:Fe. 150 keV Si ions and 160 keV P ions were implanted with doses ranging from 1×1013 to 1×1015 / cm2 at room temperature, 200℃ and 77K. Thermal annealing was performed in a conventional open tube furnace under flow of pure N2 for 15 minutes. Annealing temperature was chosen from 150℃ to 800 ℃ It was found that a dose of 8×1013cm2 Si+ was sufficient to produce an amorphous layer at room temperature and its epitaxial regrowth takes place at temperature below 150 ℃. The epitaxial regrowth of amorphous layer produced by 1×1014/cm2 Si ions occurs from both substrate and surface while that produced by co-implantation of 1×1014 /cm2 Si ions with the same dose of P ions takes place from substrate only. It was also noticed that for the former sample, its amorphized layer can be nearly completely recrystallized by epitaxial growth at 650 ℃, but for the latter much residual disorder remains even after annealing at 750 ℃. As for 77K implant at dose as low as 5×1013/cm2, Si ions begin to produce an amorphous layer that can be wholly reordered at 750℃. Samples implanted at 200℃remain crystalline only with small fraction of disorder due to self-annealing effect during the implantation. The damage annealing in the implanted layer corresponds to the change of electrical parameters got from Hall measurements.     

低轨卫星扩频系统中的PN码混合并行捕获技术研究

以低轨卫星信道多普勒特性为背景,给出一种适用于大频偏条件下突发通信系统直接扩频序列混合并行捕获结构,并以门限信噪比下平均捕获时间最小为设计目标,对检测积分时间和判决门限设置进行讨论,给出最优配置方案。     

多波束天线通道幅相一致性校正及实现

本文针对多波束天线接收机的通道幅相一致性校正,提出了一种基于自适应算法的校正方法并在FPGA中实现了该方法.在满足系统要求的前提下,该方法不但实现起来相对容易,而且算法的精度和动态范围也有一定的保证.仿真和试验结果表明,该方法是可行的.     

一株耐高乙醇和低pH己酸产生菌Lysinibacillus fusiformis- pBE3-ep-SigB的构建

以Lysinibacillus fusiformis为出发菌,分别转染SigA和SigB突变基因,获得耐高乙醇和低pH胁迫的优良己酸产生菌。以pET32a（+）-SigA/SigB为模板,采用均匀试验优化SigA/SigB易错聚合酶链式反应（ep PCR）扩增体系中的Mn2+和Mg2+浓度,通过ep PCR获得ep-SigA/SigB突变基因,与载体pBE3-MCS连接后,构建L. fusiformis-pBE3-ep-SigA/SigB突变菌体库,将两种菌体库在pH值2～5和乙醇含量2%～12%条件下进行筛选。结果表明,L. fusiformis-pBE3-ep-SigB重组菌株耐受最高乙醇含量为8%左右,最低耐受pH值为2.5左右;当乙醇含量为8%、pH值为3.5时,L. fusiformis-pBE3-ep-SigB重组菌株的己酸产量达到（254.35±39.74） mg/100 mL,显著高于工程菌株L. fusiformis-pBE3-ep-SigA的己酸产量（P＜0.01）,且为出发菌L. fusiformis己酸产量（93.62±10.33） mg/100 mL的271.68%,表明L. fusiformis-pBE3-ep-SigB重组菌株具有较强的抗高乙醇浓度和低pH值胁迫产己酸的能力。     

通信信号数字调制方式自动识别算法研究

自动调制识别是非协调通信系统接收机设计中的重要研究课题,该文针对工程中的应用提出了一种调制识别算法。与已有的算法相比,该算法结构简单,计算量小,适合实时计算,而且在低信噪比环境下有较高的识别准确度;同时考虑了符号成形对参数提取的影响,更能满足工程上的需要。     

一种大频偏和低信噪比条件下的全数字锁相环设计

全数字锁相环设计是相干解调全数字接收机载波同步和位同步的关键技术,而大频偏和低信噪比分别从两个方面增加了环路设计的难度.该文在此背景下,以捕获时间和跟踪性能为指标,从模拟环路分析出发,给出一种适用于大频偏和低信噪比条件的全数字锁相环设计.