新型无本振毫米波光纤无线通信上变频系统

基于低速信号注入法-珀(FP)激光器可实现无微波本振光纤无线通信(RoF)上变频技术,但是得到的微波本振频率受到FP激光器中四波混频效率的限制,难以直接实现毫米波载波的RoF上变频。在注入锁定FP激光器的基础上提出了一种新型的、低成本的在光域直接产生毫米波载波的RoF上变频方案。由于注入锁定FP激光器过程中的动态载流子特性,上变频得到的载波信号带有正啁啾,故可用负色散介质对载波信号进行脉冲压缩,从而增强高阶谐波分量以完成毫米波载波的无本振RoF上变频。实验中采用2 Gb/s非归零码注入实现了载波为13.9 GHz,用2.5 Gb/s注入实现了载波分别为13.9 GHz和15.4 GHz的RoF上变频,并采用上述方案分别实现27.8 GHz和30.8 GHz的倍频载波分量的增强。进一步实验验证了用本方案实现载波频率约60 GHz可调谐毫米波的无本振RoF上变频的可行性。     

利用基带直调信号注入锁定半导体激光器产生全光上变频信号的研究

提出了一种将低速基带信号直调产生的宽谱信号,注入至用于上变频的分布反馈式半导体激光器(DFB-LD),利用调制信号光谱中的高阶分量对从激光器进行相位锁定,从而产生光学上变频信号的方法。对直调信号注入锁定DFB-LD产生光学上变频信号的机理进行了理论分析,完成了2.5Gb/s伪随机码基带信号通过直调并注入从激光器,分别产生了30,35,40GHz副载波频率的全光上变频信号的实验,并在时域和频域上,对上变频信号的特征进行了研究。该方案结构简单,无需高速外调制器及高频本振,具有集成潜力,理论上可产生更高载频(如60GHz),对目前的光-无线混合接入提供了一种可行的解决方案。     

基于低速光调相信号注入DFB-LD产生4～16倍频的40GHz和60GHz毫米波信号

提出一种基于低速光调相信号注入半导体分布反馈激光器(DFB-LD)产生最低4倍频,最高16倍频的40GHz和60GHz的毫米波调相信号。该方案利用注入光的N阶调相边带锁定DFB-LD的波长,同时DFB-LD放大此调相边带并与原注入光信号通过相干差拍作用在LD腔内形成毫米波调相信号。通过理论建模分析了工作原理,经系统实验验证了此方案的可行性。应用2.5,5和10GHz的光调相信号均得到40GHz或60GHz的毫米波信号,实现了最低4倍频,最高16倍频的毫米波信号产生,并通过单边带相位噪声的测量验证了毫米波的频率稳定度。     

基于FP-LD实现副载波信号产生

采用一种基于法布里-珀罗腔激光二极管(FP-LD)的副载波信号的产生方案,此方案主要包括一个FP-LD和一个电光相位调制器(PM)。首先利用可调谐激光器、电光PM及微波源产生光正弦相位调制信号,将该信号注入到FP-LD中,通过FP-LD的注入锁定将该信号转换为副载波信号。在实验中,分别以2、3、4和5 GHz的调制频率注入到FP-LD中,相应得到22、21、24和25 GHz的副载波信号。     

基于压缩脉冲载波的远端上变频光载射频系统

提出并实现了一种用光纤色散压缩脉冲为载波的上变频射频光载系统。该系统把传统的连续光载波替换为频率啁啾脉冲,利用传输光纤色散压缩脉冲宽度,增强谐波分量,使脉冲载波上的信号在接收端转换到脉冲高次谐波上,从而实现了远端上变频。该方法的特点是用低频本振就可实现高频微波信号的产生,发射端无需电倍频器、混频器,接收端只需用滤波器选择所需频率信号,系统结构简单。应用该方法实现了2Gbit/s信号经60km普通单模光纤传输后远端上变频到16GHz、经过5.4m无线传输后误码率低于10-8的射频光载系统,系统中只有一个光功率放大器,无光在线和预放大以及光滤波器和色散补偿。     

ROF系统中基于SOA非线性效应的光子上变频技术研究

在光载射频（ROF）系统中,为了将承载信息的光基带信号上变频到微波／毫米波波段,本文基于半导体光放大器（SOA）中的交叉增益调制（xGM）和交叉相位调制（XPM）效应实现了光子上变频：即实现了1．25Gb／s基带信号到30GHz的毫米波信号的转换。文中分析了SOA驱动电流的变化（50～200mA）和信号光与本振光波长间...     

基于注入锁定的RF低功耗正交本振信号产生电路

实现了一个基于注入锁定技术的射频低功耗正交本振信号产生电路.该电路由工作于两倍频频段的压控振荡器和两个注入锁定二分频器及缓冲器构成,可以为无线收发机提供正交本振信号.通过采用数字调谐技术,压控振荡器达到了很宽的调谐范围,而通过在注入锁定二分频器中加入与压控振荡器相同的变容管和电容阵列,保证了注入锁定二分频器在整个频带范围内都能保持锁定.该正交本振产生电路采用UMC 0.18 μm CMOS工艺实现.测试结果表明,在1.9～2.3 GHz频率范围内,该电路能够提供正交本振信号.该电路采用1.8 V电源供电,消耗的电流为2.2 mA(不包含缓冲器的电流),占用芯片面积为1.56 mm2.     

频谱分割ASE注入波长锁定FP-LD的研究

文章分析了频谱分割放大自发辐射(ASE)注入波长锁定法布里-珀罗激光器(FP-LD)光谱随注入种子光光功率的变化情况.实验研究了ASE频谱分割光源注入波长锁定FP-LD的增益和边模抑制比(SMSR)随注入ASE光功率以及FP-LD注入电流的变化关系.最后比较了经过不同频谱分割方法的注入波长锁定光信号在波分复用-无源光网...     

频谱分割ASE带宽对注入锁定FP-LD性能的影响

注入锁定FP-LD被认为是WDM-PON无色ONU的一种低成本解决方案并受到广泛关注.结合频谱分割ASE噪声与其带宽的关系,实验对比了不同带宽种子光注入下FP-LD的输出特性差异,并综合考虑AWG的滤波效应得出了注入频谱分割ASE带宽优化时需要考虑的问题.     

Free-space optical distribution of local oscillator signals inaperture synthesis radio telescope arrays

An alternative to individually phase-stabilised links for distribution of local oscillator (LO) signals in large arrays of radio telescopes is considered. An array is illuminated from an elevated optical source, intensity modulated at the LO frequency. LO phase feedback from the centre of the illuminated zone counteracts tower and atmospheric instabilities, locking a fixed phase at zone centre, and hence a template of constant phase contours around the zone centre point. Other LO detector planes are aligned to equiphase contours, providing a phase coherent LO to all telescopes aside from differential optical path effects. A local PLL at each site reduces the remaining noise from differential slant path variations     

Impact of local oscillator intensity noise on performance of coherent subcarrier multiplexing system using common local oscillator (CLO)

The impact of local oscillator intensity noise on the performance of a coherent subcarrier multiplexing (CSCM) system using a common local oscillator (CLO) is analysed. For a given LO power, RIN noise, and thermal noise, the CNR can be expressed in terms of x, the ratio of sigma /sub sh//sup 2/+ sigma /sub th//sup 2/ over sigma /sub RIN//sup 2/ and, for x<<1, the CNR decreases as LO power increases; for x>>1, the CNR increases as the LO power increases; as x approaches 1, there exist an optimum value of local oscillator power and a corresponding maximum CNR. For a system with RIN=-150 dB/Hz, P/sub S/=-20 dBm, beta =0.02, N=40, NF=3 dB and B=10 MHz, the (P/sub LO/)/sub opt/ is found to be -4 dBm and (CNR)/sub max/ 22.5 dB.<>     

外腔振荡式光纤激光光谱合成系统

光谱合成技术是一种有效的突破单根光纤激光器输出极限,得到更高亮度的激光输出的方法。介绍了一种外腔振荡式单路光源的光纤激光光谱合成方案,相比于现行的主振荡功率放大（Master Oscillator Power-Amplifier,MOPA）式单路光源的单光栅合成方案,具有结构紧凑、阵列规模扩展能力强的优点。对该方案进行建模,分析了合成系统中不同波长的单路激光光源的位置关系,并对系统中的光纤排布、转换透镜像差等因素对合成效果的影响进行了仿真计算。搭建实验系统进行了初步的实验验证,与理论结果能够吻合。对下一代光谱合成系统的构建以及光学元件的选择具有重要的指导意义。     

变换域通信系统信号基函数的盲同步估计方法

为了解决当收发两端频谱环境不一致时,变换域通信系统(TDCS)基函数序列的盲同步估计问题,文章提出了一种TDCS信号盲同步的改进算法。相比于传统的基于F_范数盲同步法系统性能明显改善。将接收到的TDCS信号进行周期分段以形成连续多个观察向量,分段向量通过改进算法估计采样延时。同步后将接收信号按基函数周期分段得到分段向量,求协方差矩阵并累加平均,最后通过特征值分解法得到最大特征向量即估计的基函数序列。仿真结果表明:估计的基函数相关解调接收信号得到的误码率与收发两端基函数一致条件下的误码率基本一致。     

浅谈国产交换机如何接入本地网管集中监控系统

较详细地介绍了几种国产交换机接入TIMS系统的方案，此方案已实施。     

Bit-error rate of PSK heterodyne optical communication system and its degradation due to spectral spread of transmitter and local oscillator

In a PSK heterodyne optical communication system, the FM noise of the transmitter and local oscillator degrades the bit-error rate (BER). A theory is presented giving the BER of such a system considering the FM-noise effect. To verify the theory, BER measurement is performed using a simulation model of the PSK heterodyne system.     

Elimination of quadratic drift errors in system identification by pseudorandom binary signals

Use of the reference phase of a pseudorandom binary signal in a linearly weighted crosscorrelation is shown to result in the elimination of errors due to both linear and quadratic disturbances in the estimation of a system weighting function.     

Investigation of the micro-step control positioning system performance affected by random input signals

This paper gives the results of simulation and experimental investigation on the effects of random signals on the accuracy of micro-stepping control positioning. For studying and simulation of the effect of random noise signals on performance of the accurate position control systems, such as Hybrid Stepper Motors (HSMs), a micro-step driver and controlling unit using PID controller has been designed and constructed. Several parametric studies have been carried out including different white noise power and micro-step per revolution. Tracking problem for a HSM model has been simulated, and the experimental study for similar cases has been carried out by implementing the designed controller in real-time operation by using Real Time Windows Target Toolbox of Matlab software and Simulink. Simulation and experimental results show that random noise source changes current profile and affects the accuracy of positioning. Performance of the proposed PID controller under the implementation of random noise on phases one and two of stepper motor has been proved to be accurate enough even under disturbance load currents, on the system. Experimental and simulation results show the good performance of designed controller in tracking problem, affected by various random noise powers and motor speeds in different micro-step positions. Moreover there is an excellent agreement between experimental and simulation results.     

以微波方式进行电视信号传输时的系统指标分析.

系统阐述了影响微波传输的各种外界因素及微波传输特性,并且根据这些外界因素和传输特性对微波传输性能,传输余隙,噪声,损耗及电平裕量等进行了系统分析。     

KFM detection of charges injected by AFM into a thin SiO2 layer containing Si nanocrystals

Charge retention of Si nanocrystals elaborated by ultra-low energy ion implantation and thermal annealings into a thin SiO₂ layer is characterized by atomic force microscopy (AFM) and Kelvin force microscopy (KFM). Electrons and holes are injected under ambient conditions by applying different bias to a conductive AFM tip in contact with the grounded sample. A surface potential mapping of the sample by KFM is continuously carried out after charge injection. The temporal decay of injected charges and their corresponding lateral spreading are quantified. The results show that the presence of Si nanocrystals leads to a strong charge confinement.