移动通信网络中的无线电干扰问题处理

1干扰的概念和分类根据无线电干扰形成的原因,移动通信系统中的无线电干扰可分为同频干扰、邻频干扰、互调干扰和接收机减敏(或阻塞干扰)等。干扰可以使系统的底噪抬升,影响网络质量,严重时可以使网络阻塞。本文重点对阻塞类干扰进行分析。阻塞干扰是指当存在一个能进入接收机,并能作用于其前端电路的强干扰信号时,由于接收机前端电路的非线性而造成对有用信号增益降低或噪声增高,使接收机产生接收灵     

雷达之间的干扰及概率计算

两部雷达在天线对准时会产生相互影响,严重时可能出现烧毁接收机前端的现象。本文分析了雷达之间的电磁兼容问题,给出了干扰信号强度的计算方法。研究了各种雷达天线对准概率的计算方法,并给出了计算实例。     

基于捕获结果的GNSS欺骗式干扰检测

GNSS欺骗式干扰是卫星导航系统的一大威胁。对于转发式欺骗干扰,由于目标接收机并不知道所受干扰的具体参数,现有的单一欺骗检测方法不能检测所有欺骗干扰,本文提出一种在捕获阶段检测欺骗干扰的组合算法。首先利用联合信干噪比和多峰检测方法进行检测。如果捕获峰值超过给定阈值,则有欺骗干扰信号存在;若未超过给定阈值但有两个峰值,则利用提出的码相位差一致性方法进行检测,该方法避免了多径信号对检测性能的影响;当只有一个未超过给定阈值的峰值时,可能存在真实信号和欺骗干扰信号重叠,此时通过改进的相关函数宽度阈值方法进一步检测。当有两个相关峰时,随着欺骗干扰信号总功率变小,检测概率越来越高,表明了码相位差一致性方法的有效性;当有一个相关峰时,对于不同小时延下的转发式欺骗干扰信号,检测概率较高,表明了改进的相关函数宽度阈值方法的有效性。      

对 ELINT 系统信道化接收机的干扰技术研究

介绍了ELINT系统的信道化接收机的相关特性,讨论了己方雷达信号分别为线性调频体制及常规体制时,不同的干扰信号对接收机测频性能的影响:当雷达信号为线性调频体制时,采用线性调频干扰信号,满足合适的时序关系,使得接收机测出的信号带宽展宽;当雷达信号为常规体制时,干扰信号为线性调频或频率捷变体制,使得接收机对雷达体制判断错误。通过仿真验证了干扰效果,保护了己方雷达信号的技术参数不被正确获取,从而进一步提高了雷达的生存性能。     

雷达之间相互干扰的计算机仿真

分析了雷达之间存在的干扰,给出了干扰信号幅度的计算公式和干扰阈值的估算方法。为了有效地研究雷达之间的干扰情况,建立了2部雷达之间相互干扰的计算机仿真模型。简述模型的组成及各模块的作用。通过计算机仿真,研究2部具体雷达相互干扰的情况。仿真结果表明,距离很近的两部雷达,当主波束对准时会出现硬件损伤现象。     

对ESM系统副瓣抑制接收机的干扰方法研究

针对我方雷达信息易被敌方电子对抗支援侦察(ESM)系统获取的问题,通过分析ESM侦察系统中副瓣抑制接收机的工作原理,提出一种相干干扰的干扰方法,使我方雷达信号到达敌方侦察设备后同干扰信号一起被接收机滤除,从而降低敌方侦察我方雷达信息的能力。在相干干扰机理研究的基础上,对相干干扰所需的最小强度（临界强度）及其影响因素进行了推导分析,并通过仿真得到了干扰入射角度和相位差对临界强度的影响效果,以及使临界强度最低的最优干扰条件。     

对空时自适应处理雷达的投散射式伪杂波干扰方法信号特性分析

针对宽带噪声干扰在空时自适应处理（Space-Time Adaptive Processing,STAP）雷达功率凝聚工作模式下无法有效掩护被保护目标方位信息的问题,提出了一种投散射式伪杂波干扰方法,分析了干扰信号在雷达接收端的空时特性.该方法通过向地面特定区域投射经过调制转发的雷达信号产生类杂波干扰信号.该信号多普勒频率与方位耦合、具有空间连续性与时间连续性,空时功率频谱轨迹可控.推导了干扰信号空时矢量模型,从雷达接收机的角度分析了干扰给目标检测带来的影响;在研究干扰信号多普勒轨迹分布特性与等值多普勒曲线分布特性的基础上,提出了干扰空时协方差矩阵特征值数目估计方法.仿真结果表明,该方法产生的干扰空时功率谱呈背脊线分布,使STAP处理器出现多个凹口,有效保护了目标信息.     

信道化接收机的梳状干扰效果分析

分析了雷达侦察系统中信道化测频接收机的原理和关键技术。从雷达反侦察的角度考虑,提出"进攻性反侦察"的梳状谱干扰方法,使干扰信号和雷达信号同时进入信道化测频接收机,达到破坏其测频结果的目的。通过对干扰效果仿真,验证了该方法的有效性。     

多通道电子对抗接收系统

本发明叙述电子对抗系统,着重阐述多通道反干扰雷达接收机,这种接收机能够自动识别不同干扰信号的噪声特性。搜索雷达系统通常包括反干扰电路,这是为了当回波信号和波长相同或者几乎相同的干扰信号同时出现在接收机时,保证在示波器的荧光屏上得到一个满意的回波图像。鉴于干扰信号可利用不同的形式,在回波脉冲与干扰信号之间要获得一个有效的视频显示和一个有用     

交叉眼干扰数学建模

对单脉冲跟踪雷达在交叉眼干扰环境下所接收信号模型及所测目标视角进行了较严格的数学分析和初步仿真计算.结果表明:1)单脉冲跟踪雷达所接收信号中的干扰信号分量与目标回波信号分量间存在多普勒频差,多普勒频差随雷达与目标间距离的减少而增大;2)当目标回波信号功率相对于单个干扰信号的功率不是足够小时,目标回波信号可能导致诱偏方向失控;3)尽管当两干扰信号功率完全相等,相位正好相反时,交叉眼干扰对单脉冲跟踪雷达的诱偏能力最强,但如此设置干扰参数并不能达到预期干扰效果.     

Design and analysis of a high-sensitivity optical receiver forSONET OC-12 systems

In this paper, we will present the design and analysis of a high-performance lightwave receiver front end for SONET OC-12 applications. The receiver is designed to be operated with the standard +5 V and -5.2 W power supplies, and can be incorporated into an existing commercially available full receiver package. The full receiver achieves a sensitivity of better than -44 dBm at a bit error rate of 1×10 ^-9 over the whole operating temperature range of 0°-65°C. The construction and performance of the receiver will be discussed in detail in this paper. As a part of the process of design consideration, we will also discuss the S-over-X measurement, a characterization procedure for ISI (intersymbol interference) simulation and eye-opening estimation, frequently used for SONET or SDH subsystems yet not often discussed in the literature. The interpretations of the results of the S-over-X measurement are sometimes very misleading. Examples included in this paper will help the lightwave subsystem vendors and customers to have a better perspective on the S-over-X measurement process     

接收前端信道设计中的一些考虑

介绍了接收信道前端在微波转发设备中的重要性,给出了信道前端设计的框图,介绍了各部分电路在接收信道中起的作用,讨论了接收机中混频器／本振、放大器性能和系统噪声系数设计、组合干扰产生等方面对接收机性能的影响,同时强调了设计中应该注意和兼顾考虑的地方。     

A Linear Prediction Based Estimation of Signal‐to‐Noise Ratio in AWGN Channel

Most signal‐to‐noise ratio (SNR) estimation techniques in digital communication channels derive the SNR estimates solely from samples of the received signal after the matched filter. They are based on symbol SNR and assume perfect synchronization and intersymbol interference (ISI)‐free symbols. In severe channel distortion where ISI is significant, the performance of these estimators badly deteriorates. We propose an SNR estimator which can operate on data samples collected at the front‐end of a receiver or at the input to the decision device. This will relax the restrictions over channel distortions and help extend the application of SNR estimators beyond system monitoring. The proposed estimator uses the characteristics of the second order moments of the additive white Gaussian noise digital communication channel and a linear predictor based on the modified‐covariance algorithm in estimating the SNR value. The performance of the proposed technique is investigated and compared with other in‐service SNR estimators in digital communication channels. The simulated performance is also compared to the Cramér‐Rao bound as derived at the input of the decision circuit.     

一种IR-UWB系统FS-DFME均衡接收机

该文针对在密集多径室内环境中超宽带(UWB)信道的延迟扩展时间长,脉冲超宽带(IR-UWB)系统在高速数据传输时码间干扰(ISI)严重致使误码率(BER)增加以至于系统无法工作的问题,基于ISI的成因,提出了一种分数间隔判决反馈居中均衡(FS-DFME)均衡接收机,该均衡接收机能够联合实现匹配滤波和信道均衡,从而能够有效地收集多径信号能量和抑制ISI影响。研究结果表明均衡接收机的观察窗口长度是影响ISI消除效果的重要参数;与线性均衡(LE)和分数间隔判决反馈非居中均衡(FS-DFNME)均衡接收机相比,FS-DFME均衡接收机能够更加有效地消除ISI,提高系统的BER性能。     

Adaptive array processing for multipath fading mitigation viaexploitation of filter banks

We propose subband adaptive array processing for mitigation of both intersymbol interference (ISI) and cochannel interference (CCI) in digital mobile communications. Subband adaptive array processing employs filter banks in a front end to an adaptive array receiver. By decomposing the signals into a set of subband signals, the analysis filters enhance the correlation of multipath rays in each subband. This enhancement is blind in the sense that no a priori knowledge of the temporal characteristics or spatial signatures of arriving signals is required. With the increased coherence, the desired signal can be effectively equalized by subsequent spatial processing. Further, the CCI signals and their multipaths can be suppressed with fewer degrees of freedom. The effects of quadrature mirror filter and discrete Fourier transform filter banks on multipath correlation are delineated     

An efficient receiver scheme for downlink ZP-CDMA

A signal transmitted through a wireless channel may be severely distorted by intersymbol interference (ISI) and multiple access interference (MAI). In this paper, we propose an efficient CDMA receiver based on frequency domain equalization (FDE) with a regularized zero forcing (RZF) equalizer and parallel interference cancellation with a unit clipper decision function (CPIC) to combat both the ISI and the MAI. We call this receiver the FDE-RZF-CPIC receiver. This receiver is suitable for downlink zero padding CDMA cellular systems. The effects of the decision function, the channel estimation, the number of cancelled users, and the user loading on the performance of the proposed receiver are discussed in the paper. The bit error rate (BER) of the data received by the proposed receiver is evaluated by computer simulations. The experimental results show that the proposed receiver provides a good performance, even with a large number of interfering users. At a BER of 10^?3, the performance gain of the proposed receiver is about 2 dB over the RAKE receiver with a clipper decision function and PIC in the half-loaded case (eight users) and is much larger in the full-loaded case (16 users).     

Differential detection via the Viterbi algorithm for offsetmodulation and MSK-type signals

The differentially coherent reception of two families of constant-envelope signals, the linear offset quaternary phase shift keying and the binary partial response continuous phase modulation with index 0.5, is addressed. When the conventional (PSK-type) differentially coherent detector is used, a large performance degradation, compared with that of coherent receiver, is observed. The reason for this is the presence of an inherent intersymbol interference (ISI) in the signal and also noise enhancement and correlation introduced by the receiver filter. A differential detection strategy which compensates for ISI and avoids noise enhancement is presented. A phase estimate that takes into account the presence of the inherent ISI is derived. This phase estimate is then used in the decision metric of a coherent receiver. The resulting decision rule can be implemented using the Viterbi algorithm. Simple Viterbi receivers with good performance are obtained. Simulation results are given     

运动平台雷达信号相互干扰研究

当雷达间距离过于靠近时，可能存在着相互干扰。文中首先介绍了运动平台防止雷达信号相互干扰而采取的措施，然后介绍了几种典型的雷达信号及其表达形式，研究了它们本身以及相互之间的干扰问题，通过仿真得到了一些定量的数据，分析表明通过对雷达信号的优化设计可以减小它们之间的相互干扰，从而克服雷达间的相互影响。