Narrowband interference suppression in TR-UWB system based on cognitive radio theory

A cognitive radio transmitted reference ultra-wideband（CR-TR-UWB） system is proposed to improve the performance of TR-UWB systems with narrowband interference（NBI） from primary users（PU）.The transmitter of the CR-TR-UWB system detects the band of PU,and then sends prolate spheroidal wave functions（PSWF） pulses with the same limited band as PU＇s to reduce interference with PU.The receiver uses a notch filter before autocorrelation to eliminate NBI from PU.The simulation results show that the bit error rate（BER） performance of the CR-TR-UWB system is close to that of TR-UWB systems without NBI when the system is interfered by single or double NBIs with a signal to interference ratio（SIR） of 0 dB,and if the signal to noise ratio（SNR） is 10 dB and the SIR varies from-20 to 10 dB,BER performance varies no more than an order of magnitude.The system has excellent resistance to NBI,strong robustness BER performance at different SNRs,and smaller interference with the same frequency band PU.

New Technique for Estimating and Suppressing Narrowband Interference in DSSS Systems

A generalized approach for narrowband interference （NBI） suppression in direct sequence spread spectrum （DSSS） communication systems using adaptive infinite impulse response （IIR） filter is presented. The excision filter coefficients depend on both the jammer power and its instantaneous frequency. The dependency of the filter construction on the jammer power is significant as it allows optimal tradeoff between interference removal and signal distortion by maximizing the receiver signal to noise ratio improvement（SNRI）. Instead of traditional adaptive line enhancer （ALE） estimator, a preferable NBI estimator-Fourier interpolation estimator （FIE） is proposed. Closed-form expressions of the SNR improvement and theoretical bit error rate （BER） based on the assumption that the output of the correlator is Gaussian distributed are both derived. Performance results obtained by numerical simulation are also presented and compared with theoretical results.

New Kalman Filtering Algorithm for Narrowband Interference Suppression in Spread Spectrum Systems

A new Kalman filtering algorithm based on estimation of spread spectrum signal before suppression of narrowband interference （NBI） in spread spectrum systems, using the dependence of autoregressive （AR） interference, is presented compared with performance of the ACM nonlinear filtering algorithm, simulation results show that the proposed algorithm has preferable performance, there is about 5 dB SNR improvement in average.

Data-Aided Frequency Offset Estimation with Narrowband Interference

An algorithm for carrier frequency offset estimation with narrowband interference in burstmode transmissions is proposed.The algorithm is data-aided and has a feedforward structure that can be easily implemented digitally.The principle of the algorithm is based on a properly designed training sequence and an interpolation technique.Simulation results indicate that the estimation range is about ±20% of the symbol rate.The performance is satisfactory for a signal-to-noise ratio（SNR）as low as -13 dB and the mean square error（MSE）is approximately irrelevant to signal-to-interference ratio（SIR）values over -20 dB.

Modulated Lapped Biorthogonal Transform for Non-orthogonal Narrowband Interference Excision in Spread Spectrum Communications

Traditional lapped transform domain excision techniques obtain good performance at the expense of increased processing delay. Extension of transform domain filtering techniques to the lapped biorthogonal transform domain can help solve the problem. By incorporating biorthogonality into the lapped transforms, more flexibility is obtained in the design of windows. Thus transform bases with better stopband attenuation can be generated by designing windows, but not by increasing the overlapping factor. In this paper, a new modulated lapped biorthogonal transform (MLBT) with optimized windows is introduced for efficient compression of multi-tone interfering signal energy. The bit error rate (BER) performance of the receiver employing the proposed MLBT excision technique is analyzed and compared with that of the lapped transform domain excision-based receivers. Simulation results demonstrate the improved performance and increased robustness of the proposed technique.

Ultra-wideband direct-sequence design approach for multiple narrowb and interference suppression

A novel direct sequence （DS） design method for suppressing the narrowband interference in DS spread spectrum ultra-wideband receivers is proposed. The method has low computational complexity and can be easily implemented in practical systems. Simulation results prove that the proposed method is effective to suppress the narrowband interference. Therefore, the integrity of both the ultra-wide bandwidth and the narrowband systems can be highly enhanced.

QPSK DS-CDMA System over Rayleigh Channel with a Randomly-Varying Frequency Narrow-Band Interference: Frequency Tracking Analysis

This paper analyses frequency tracking characteristics of a complex-coefficient adaptive infinite-impulse response (IIR) notch filter used for suppression of narrow-band interference (NBI) with a randomly-varying frequency in a quadriphase shift keying (QPSK) modulated direct-sequence code-division multiple-access (DS-CDMA) communication system. The QPSK DS-CDMA signals are transmitted over a frequency non-selective Rayleigh fading channel. The analysis is based on a first-order real-coefficient difference equation with respect to steady-state instantaneous frequency tracking error from which a closed-form expression that relates frequency tracking mean square error (MSE) with number of DS-CDMA active users and NBI power is obtained. Closed-form expressions for optimum notch bandwidth coefficient and step size constant that minimize the frequency tracking MSE are also derived. Computer simulations are included to substantiate the accuracy of the analyses.

改进的传输参考型超宽带系统抗NBI性能

为研究带有有限长脉冲响应陷波滤波器(NF)的传输参考型超宽带系统(TR-UWB)的抗窄带干扰性能,在IEEE 802.15.3a建议的标准超宽带信道下,分析比较了在不同参数设置下,该系统自相关接收机的误比特性能。仿真结果表明,带有陷波滤波器的传输参考型超宽带系统能够有效降低窄带干扰,并且系统接收机结构简单,无需信道估计,大大降低了计算量和系统复杂度。

面向海战场综合通感系统的窄带干扰抑制算法

本文构建了一个集成的通信和感知系统,该系统具有感知目标并与用户通信的能力,并针对雷达探测性能和通信性能的平衡进行了优化。在海战场通信环境中,信号在传输过程中经常受到窄带干扰的影响,对通信质量造成很大损害。针对这一问题,本文设计了一套结合综合通信感知系统的窄带干扰抑制算法。该算法对经典阈值算法进行改进,实现阈值自适应。最后通过仿真说明了窄带干扰的危害以及去除窄带干扰的必要性,将窄带干扰下信号的误码率与本算法处理的信号进行比较,证明算法的有效性,将该算法与传统算法进行对比,证明了算法性能的提高。

基于PSO-SVM的高温炉变频电机局部放电预警监测方法

在高温炉加热过程中,非均匀的暂态随机状态会影响高温炉变频电机局部放电信号时间特性,导致时间一幅值关系的离散变量不能确定而影响监测效率,为此提出基于PSO-SVM的高温炉变频电机局部放电预警监测方法。首先,采用奇异值分解(SVD)抑制高温炉变频电机局部放电信号中的窄带干扰,获取有用信号;其次,利用局部线性嵌入(LLE)算法提取降维信号中的局部放电特征参数;最后,将其作为输入特征向量构建基于粒子群优化的支持向量机分类函数(PSO-SVM),完成对高温炉变频电机局部放电类型的识别和监测,并以此为依据求出局部放电阈值预警参数和趋势预警缺陷水平,实现对高温炉变频电机局部放电的预警监测。实验结果表明,所提方法能够有效抑制局部放电窄带干扰,并在一定程度上提高了高温炉电机局部放电信号的识别精度和预警监测效率。

基于能量检测和NBI消除的UWB接收机信号检测

针对基于能量检测的超宽带（UWB）接收机提出了信号检测算法,此系统使用了平方率（SL）窄带干扰（NBI）消除技术来去除窄带干扰。由于使用能量检测方案,因此在高斯白噪声的情况下,统计检测量可以表示为统计独立的高斯随机变量的平方和。当有用信号不存在时,统计检测量服从中心χ^2分布,其自由度为积分器输入信号的二倍时间—带宽积。当有用信号存在时,统计检测量服从自由度相同的非中心χ^2分布,且依赖于因子λ。λ和系统参数有关,这些参数包括有用信号的能量和带宽,干扰信号的功率谱密度和带宽,以及噪声的功率谱密度。非中心的χ^2分布通过检测门限和自由度的转化可以化为中心χ^2分布。MATLAB数值计算显示了接收机工作特性（ROC）曲线,即检测概率Qd和虚警概率Q0的关系。从图中曲线可以看出,系统的参数和检测性能密切相关,比如当系统带宽变动时,虚警概率可以保持不变,而检测概率可能变为原来的2倍。结果表明,可以通过改变系统参数得到期望的检测性能。

BER of OFDM System with Multiple NBI Rejection Cascade Complex Coefficient Adaptive IIR Notch Filter

In this paper, rejection of multiple narrowband interferers in a binary phase shift keying modulated orthogonal frequency division multiplexing (BPSK-OFDM) system is investigated. The BPSK-OFDM system in consideration operates in an additive white Gaussian noise (AWGN) channel. A cascade complex coefficient adaptive infinite impulse response (IIR) notch filter with gradient-based algorithm is used to reject the interferers. Bit error ratio (BER) performance of the system is studied and a general closed-form expression is derived assuming negligible steady-state leakage NBI and by estimating the decision variable as Gaussian distributed based on Central Limit Theorem (CLT). Dependence of the BER performance on the notch bandwidth coefficient is demonstrated by the analysis. Extensive simulation results are included to substantiate accuracy of the analysis.

窄带干扰及动态环境BOC调制信号多通道并行捕获

针对窄带干扰及动态环境二进制偏移载波(binary offset carrier,BOC)调制信号捕获困难、捕获效率低的问题,提出利用奇异值分解(singular value decomposition,SVD)结合最小描述长度(minimum description length,MDL)准则对窄带干扰进行抑制。在部分匹配滤波器结合分数阶傅里叶变换(partially matched filter-fractional Fourier transform,PMF-FRFT)捕获算法的基础上提出结合伪码复合以及异步伪码相关累加的多通道并行捕获算法。该算法首先对接收到的含窄带干扰信号做SVD,利用MDL准则自适应估计出干扰信号的个数并完成干扰抑制;然后,将信号伪码相加形成新的伪码序列,由PMF-FRFT结合异步伪码相关累加算法实现对多个信号的精确捕获。仿真结果表明,SVD窄带干扰抑制算法在较好保留原信号特征的基础上能够有效抑制干扰信号,且性能稳定。提出的伪码复合结合异步伪码相关累加多通道捕获的算法可同时完成多个信号的捕获,有效提升信号捕获概率、减少捕获时间。

基于广义S变换与数学形态学的局部放电窄带干扰抑制方法

针对高压电力设备局部放电信号受周期性窄带干扰影响大的问题,提出了一种基于广义S变换与数学形态学的局部放电窄带干扰抑制方法。该方法可以从染噪局部放电(partial discharge,PD)信号中分离出原始PD信号和窄带干扰信号的时频谱图,从而在时频域内准确辨识出窄带干扰和原始PD信号,避免强能量的窄带干扰掩盖原始PD信号时频特征的问题。再利用总体最小二乘不变旋转矢量技术准确估计窄带干扰的特征参数,以抑制染噪PD信号中窄带干扰。对仿真和实测PD信号开展窄带干扰的抑制测试,测试结果表明:该文所提方法可以有效分离出染噪PD信号时频谱图中窄带干扰和PD信号,提高了时频分析的准确率;同时相比于传统的快速傅里叶变换(fast Fourier transform,FFT)算法谱最小熵解卷积滤波法和自适应奇异值分解法,该文方法能够有效抑制小幅值的窄带干扰,具备更好的窄带干扰抑制效果,以恢复局放信号的波形特征。

Performance Analysis of Narrowband Interference Suppression in Orthogonal Code Modulation Spread Spectrum System

This paper analyzes the performance of both in-band and outband narrowband interference suppression in orthogonal code modulation spread spectrum system, and compares with conventional spread spectrum system at the same information transmission rate and spread spectrum bandwidth. Simulation results indicate that the antijamming (narrowband interference) performance obtained from orthogonal code modulation spread spectrum system is much better than that from conventional spread spectrum system.

非常规低压部件导致整车辐射超标整改案例

某款纯电动汽车按照GB 34660-2017要求进行整车窄带发射测试时,有多点尖峰超标。通过缩小排查范围及结合远近场测试的方法,定位到超标源并非是常见的易引起类似超标现象的低压零部件,且通过剖析超标源的工作原理,也并非典型的晶振、时钟干扰。该文系统地介绍了排查整改的全过程,分析了干扰产生的机理,提出在控制板天线芯片输出管脚直接增加电阻的整改措施,并通过限制天线发射功率来抑制干扰,整改措施易于实现且裕量充足,为量产化实施提供支持。

基于车联网宽带OFDM系统的频率分集技术研究

针对车联网应用场景特点,利用频率分集技术对传统宽带正交频分复用技术(Orthogonal Frequency Division Multiplexing,OFDM)系统中的频域资源分配方案、信道估计算法、合并机制以及最大比合并算法进行了优化与设计,并通过仿真验证了设计的有效性。仿真结果表明在窄带干扰影响下,当信噪比大于3dB时,优化后的系统误码率相较于传统OFDM系统下降2~3个数量级。上述结论说明该设计的基于车联网宽带OFDM系统的频率分集技术可以更好地应对城市环境中信号无线传输过程中遇到的问题,有巨大的应用前景。

改进的频域窄带干扰陷波器

在分析频域算法实现的基础上,引入变异系数(CV)作为一种切换准则,克服了传统傅里叶变换陷波算法的门限效应,使得系统在低干信比时关闭频域陷波算法,切换到扩频系统本身的匹配滤波器进行相关解扩;而在高干信比时切换到频域陷波算法.理论分析和仿真验证了CV作为切换准则的正确性和有效性,说明了作者提出的算法在抑制窄带干扰时具有更高的自适应性能.

超宽带脉冲信号及对窄带通信系统的干扰分析

超宽带通信的优良特性使其成为继CDMA与蓝牙技术之后倍受人们重视的通信技术,但是其极宽的频谱分布对常规通信系统的干扰也成为人们担忧的问题。首先对UWB通信常用的几种高斯型极窄脉冲进行了时域与频域的分析,尽管几种波形都有极宽的频谱,但是功率谱分布规律却不相同,对频域中业已存在的常规通信系统构成干扰的程度也不相同。通过仿真分析表明,适当地选择极窄脉冲波形及相关信号参数可有效地降低这种干扰。

UWB通信系统双正交PSWF脉冲波形设计

分析UW B脉冲波形设计原则,对基于长球面波函数(PSW F)的双正交脉冲进行研究.给出获得PSW F脉冲的两种解法,及基于PSW F的陷波设计,并用MATLAB对时域波形和功率谱进行了仿真.结果表明,PSW F脉冲具有中心频率可调、带宽可控的优点,并具有双正交性,能实现任意频点不同深度的陷波,更好地抑制窄带干扰.双正交PSW F脉冲是符合UW B通信系统要求的一种性能较理想的脉冲.