基于DDS的数字IQ调制

提出了一种基于DDS的数字IQ调制的实现方法。该方法在利用FPGA实现DDS的基础上,通过运算电路对采用DDS技术产生的两路正交数字载波信号和存储在RAM中的信号星座图的各点的同相分量及正交分量进行处理,可以实现MPSK,MQAM等多进制数字调制。该方法中IQ调制的全部过程都用数字电路完成,极大地提高了IQ调制的抗干扰性和可重复性。重点对IQ映射功能做了详细的分析和设计,最后给出了实验验证和结论。     

射频调制信号瞬时特征提取方法研究

本文研究电子对抗中射频调制信号瞬时特征提取方法。对于高信噪比(SNR)信号(SNR≥15dB),采用射频信号中频直接采样和抽取、内插方法完成信号的IQ分解和恢复;并计算信号瞬时包络和信号相位主值序列;利用信号相位解混响算法和改进的基于相位多项式系数估计的信号瞬时频率最小方差算法估计信号瞬时解混响相位和瞬时频率。文中给出具体算法描述和计算机模拟结果,利用文中的方法可以有效估计射频调制信号的瞬时特征。     

FDD射频收发机IQ不平衡的片上数字补偿方法

提出一种应用于直接变频结构FDD射频收发机IQ不平衡的片上数字补偿方法。在接收机通道与发射机通道中分别插入一个数字后校正单元与一个数字预失真单元,并结合接收机通路中的数字补偿参数检测电路,针对接收机与发射机的IQ不平衡,先后构建了负反馈环路。在上电初始化时的校准模式下,利用负反馈环路的高通特性,将补偿参数转换为直流成分并精确地提取出来。基于SMIC 0.13 μm RF CMOS工艺,该数字IQ不平衡补偿方法在一种直接变频结构的FDD射频收发芯片中得到了实现。测试结果表明,接收机和发射机的镜像抑制均达到了60 dB。在64QAM调制模式下,相比于没有补偿的情况,接收机的解调EVM从4.67%提升至2.12%,发射机的调制EVM从5.16%提升至2.3%。     

基于同步控制的多通道相参信号生成技术

针对现有射频IQ矢量调制实现多通道相参信号生成存在的不足，提出了一种基于数字同步控制的多通道高精度相参射频信号生成方案。研制工程样机进行测试，在4 GHz频段范围内实现了多个射频通道的相参信号生成，通道间相位一致性优于1.5°，相位精度优于1°，相位调整分辨率小于0.5°。     

高性能的MIMO-OFDM接收机IQ不平衡补偿新算法

在分析MIMO-OFDM接收机IQ不平衡信号模型基础上,以OFDM物理层为背景提出了一种新的时频结合的MIMO-OFDM接收机IQ不平衡补偿算法,即先在时域对IQ不平衡预补偿,然后在频域对残余的IQ不平衡进行校正.仿真结果表明:本文所提算法性能优于传统的频域补偿算法,该算法在AWGN信道下能达到理想性能,在多径衰落信道下当误比特率等于10-3时性能损失可以减小到0.5dB左右.     

星载DBF Tx射频通道幅相误差校正

为了实现精确的多波束形成,该文提出了一种补偿卫星通信多波束系统发射通道幅相误差的校正方法,该方法在发射通道中同时注入多路正交码变换的校正测试信号,通过接收多路发射机的输出信号和,在基带校正算法单元利用正交码的时间相关性和IDFT并行处理的方法,同时得到多路射频通道的校正因子,并对得到的校正因子进行了归一化处理,消除了对通道中非线性器件的影响.仿真结果表明,该方法可以有效地补偿射频通道间的幅相不一致性,校正后的波束方向图接近理想的波束方向图.     

基于光纤的分布式稳相传输技术

在分布式系统中,利用光纤进行长距离射频信号传输时会出现相位不稳定的情况。针对这种现象,采用了基于射频鉴相以及PID控制的相位校正技术,提高了射频信号传输的相位稳定度,可实现射频信号的稳相传输。试验结果显示,采用该相位校正技术具有较好的稳相传输效果:当温度变化超过30℃,传输距离2.5km时,可实现2GHz信号精度优于2°的稳相传输。同时,该方案具有结构简单,易于扩展,可用于光控相控阵、本振信号传输以及空间技术等多个领域。     

雷达IQ信号反序的判断方法

在数字阵列雷达调试时,有时会出现IQ反序的情况,这会导致调试人员误判某些功能模块的输出结果,影响调试。文章给出雷达IQ信号反序的判断方法,实现对该种问题的快速定位,从而提高调试效率。     

基于统计特征的 ＩＱ 不平衡高效校正算法

针对零中频接收机的I/Q不平衡问题,提出了一种数字域的基于统计特征的盲估计IQ不平衡校正算法,该算法利用具有循环对称特性的信号的统计特征,直接估计出系统的不平衡参数,进而完成IQ不平衡校正,相比于传统的算法,本算法具有计算复杂度低,校正精度高且不容易受到加性噪声的干扰等优点。仿真结果表明,所提算法不仅可以准确估计零中频接收机的IQ不平衡参数,还能对IQ不平衡进行有效的校正,从而提高系统的镜像抑制比。     

用误差估值累加实现组合导航系统的闭环校正

本文对目前已成为导航技术发展方向的组合导航系统提出一种新的闭环校正方法,即用误差状态估值累加抵消输出实现闭环校正,并以INS/GPS组合系统为例,说明了具体算法,给出了计算机模拟结果.这种方法兼有闭环校正和开环校正的优点,可应用于各种测距间接滤波定位的组合导航系统,颇有实用价值.     

直接数字波形合成中的镜频干扰分析

该文针对数字波形合成信号中的镜频干扰问题展开讨论,着重分析了镜频的形成机理及分布特点,说明了采样率对镜频干扰的影响。在此基础上定量分析了产生镜频干扰的采样率条件,并通过实验结果验证。该分析结果为数字波形合成中的采样率选取提供了新的理论依据。     

Optimum Combining in Digital Mobile Radio with Cochannel Interference

This paper studies optimum signal combining for space diversity reception in cellular mobile radio systems. With optimum combining, the signals received by the antennas are weighted and combined to maximize the output signal-to-interference-plus-noise ratio. Thus, with cochannel interference, space diversity is used not only to combat Rayleigh fading of the desired signal (as with maximal ratio combining) but also to reduce the power of interfering signals at the receiver. We use analytical and computer simulation techniques to determine the performance of optimum combining when the received desired and interfering signals are subject to Rayleigh fading. Results show that optimum combining is significantly better than maximal ratio combining even when the number of interferers is greater than the number of antennas. Results for typical cellular mobile radio systems show that optimum combining increases the output signalto-interference ratio at the receiver by several decibels. Thus, systems can require fewer base station antennas and/or achieve increased channel capacity through greater frequency reuse. We also describe techniques for implementing optimum combining with least mean square (LMS) adaptive arrays.     

Statistical Properties of the Output of Receivers under Interference Conditions

interference mechanisms in receivers frequently entail nonlinear phenomena which alter the information sidebands of unwanted signals admitted to the receiver. Methods are discussed for obtaining useful statistical properties of the output of double-sideband receivers in such cases, when the original unwanted signals are double-sideband modulated with "Gaussian process" information. The solution is carried out in two stages. The statistical properties at the output of the nonlinear device, where the information sidebands are no longer Gaussian, are first obtained. A method is then developed for conveniently determining the pertinent quantities at the output of the filter and detector. The firstorder moments of the output are given emphasis. From these the first-order probability densities can frequently be approximated, as they are here. Specific attention is given to second harmonic interference caused by square-law nonlinearity, and to intermodulation interference caused by cube-law nonlinearity. An example of each is worked out to show the effect of bandwidth on the moments and on the probability densities.     

High-Power Coherent Beam Combining of Two Photonic Crystal Fiber Lasers

Coherent beam combining of two large mode area photonic crystal fiber (LMA PCF) lasers is studied experimentally by using a self-imaging technique. Steady interference strips with high visibility of 35% are observed in high-power operation, which demonstrates the obvious advantages of the LMA PCF over the conventional double-clad fiber in coherent beam combining. Experiments also show that the reflectivity of coupling output mirror affects the coherent output power. The maximum coherent output power of 80 W with approximate 90% combining efficiency is achieved when the pump power is 130 W and the reflectivity of coupling output mirror is 5%.     

Response of an FM discriminator in the presence of noise and acochannel interference

An exact expression for the output autocorrelation function of an FM discriminator is derived when the input of the FM discriminator is an FM signal, cochannel interference and Gaussian noise. The modulating baseband signals for the FM signal and the cochannel interference are assumed FDM signals whose statistics are modeled by a stationary Gaussian random process. The interaction among signal, interference and noise are determined by which the NPR (noise-power-ratio) can be calculated     

基于转换矩阵的GPS相干干扰抑制技术

本文首先采用空间平滑技术消除有用的GPS信号与相干干扰信号之间的相关性,然后构造干扰转换矩阵,从而抑制干扰信号,保留有用信号和噪声。最后根据最大输出信噪比原则,获得最佳波束形成器。仿真分析表明该方法可以有效提高输出信号的信号干扰加噪声比,且对信号的DOA估计不敏感。     

引入激光回馈的双光束干涉效应的研究

提出了一种引入He-Ne激光回馈的双光束干涉系统,并在理论和实验两方面进行了研究。实验中对系统中的干涉信号及激光器尾光功率变化同时进行探测。发现当干涉仪的主回馈镜移动时,激光器尾光信号是正弦形波形,而干涉仪输出的是以双峰为一个周期的信号,双峰中一峰总是高于另一峰,并且当主回馈镜移动方向改变时,同一周期中两峰出现的顺序也随之改变。对实验现象进行了理论分析,并模拟出干涉信号及激光自身功率的变化曲线。理论分析及模拟结果与实验结果完全吻合。讨论了利用发现的现象进行测量的可行性,所提出的测量方法易于实现。     

激光回馈纳米级宽度干涉条纹

一般的干涉现象为“反射镜每移动半个波长,出现一个干涉条纹”。介绍了利用激光回馈获得纳米级宽度干涉条纹的方法。系统构成:He-Ne激光器,使用近于全反射的球面介质镜作激光器的回馈镜,且该回馈镜法线和激光束夹分量级的小角度。回馈镜沿激光束位移移动时,激光器的功率发生周期类正旋波动,即产生回馈干涉条纹。回馈镜离激光器越近,条纹越窄,以至于半波长位移中出现40个条纹。对波长为632.8 nm的He-Ne激光器而言,每个条纹宽度为7.91 nm。同时,当回馈镜的运动方向发生变化时,激光的偏振态将在两个正交的方向之间发生跳变。利用此效应,可以实现纳米分辨位移测量和回馈镜运动方向的识别。     

Design of training sequence based on IQ imbalance estimation in CO-OFDM system

In this paper, a new training sequence structure is proposed, which estimates the in-phase/quadrature (IQ) imbalance factor and channel information in coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems with phase noise caused by laser linewidth. The given training sequence structure consists of four symbols. The first two training symbols have two subsets:a non-zero subset and a zero set mirror position subset. The non-zero subset is used to estimate the channel information, the mirror position subset is used to estimate the IQ imbalance factor, and the last two symbols are also used to estimate the IQ imbalance factor at the transmitter. This method can realize independent compensation for IQ imbalance and channel distortion, and improve the system performance when the data rate is 10 Gbit/s higher than the traditional method.     

微米光栅加速度计闭环检测技术优化与设计

提出一种基于Pound-Drever-Hall(PDH)调制技术的新型闭环控制方法,优化了微米光栅加速度计的信噪比和静态检测精度.采用电磁驱动实现自校准和反馈控制,相对于静电驱动降低了功耗提升了反馈效率,解决了开环检测方式下测量范围和灵敏度不可兼得的难题.对系统光学输出的干扰源进行本质分析,通过将闭环误差信号调制到高频...