基于FPGA的窄带干扰抑制算法在GPS中的应用

针对GPS接收机有效信号弱,易受窄带干扰影响的不足,提出了一种基于FPGA的窄带干扰抑制算法的实现方案。该方案以Xilinx公司的Virtex5芯片为硬件平台,采用重叠加窗频域滤波算法和自适应多门限检测技术实现窄带干扰的实时检测和抑制,最后采用重叠相加的方法进行数据输出。测试结果表明,该设计能为GPS接收机提供至少60dB的抗窄带干扰能力。与其他窄带干扰抑制方法相比,收敛速度和信噪比损耗都得到了改善。     

基于强散射点剔除的自适应窄带RFI抑制滤波器

在低频超宽带合成孔径雷达中,VHF/UHF频段密集的窄带射频干扰(RFI)严重影响了雷达性能。常规RFI抑制滤波器在干扰频点的陷波造成了宽带信号的能量损失,抬高了点目标的距离向旁瓣。该文提出一种可减小自适应滤波器旁瓣效应的方法:通过在距离压缩域剔除场景内的强散射点,减小输入信号中的宽带目标信号能量,提高自适应谱线增强器(ALE)对窄带干扰估计的精度,再从原始信号中减去干扰即得到目标回波信号。这种剔除强散射点的方法利用了匹配滤波后宽带信号与窄带干扰的时域特性差异,能有效降低自适应滤波器的旁瓣效应。该文选择归一化最小均方误差(NLMS)算法对剔除强散射点的自适应窄带RFI抑制滤波器进行了性能评估,与传统算法的对比试验表明该方法可在抑制RFI的同时有效减小强目标的距离向旁瓣。     

DS-UWB系统中二种抑制窄带干扰的多天线接收机

直接序列扩频超宽带(DS-UWB)系统采用窄脉冲和扩频技术能够与其它无线电系统共存,但是,在进行系统设计时,必须对同频段系统的干扰加以抑制.文中在存在窄带干扰的情况下,提出一种自适应多天线Rake接收机,通过自适应调整天线合并权向量来抑制窄带干扰对系统的影响,并通过仿真实验与现有抑制窄带干扰接收机进行比较.理论分析与仿真结果表明,该接收机具有较好的环境鲁棒性,并且能够一定程度上抑制窄带系统对DS-UWB系统的干扰,保证系统接收性能.     

基于认知的UWB窄带干扰抑制

提出一种基于认知无线电的自适应超宽带窄带干扰抑制方法。基于软频谱思想,利用近似椭球波函数良好的时限-带限特性,设计出一种能够抑制窄带干扰的脉冲波形。通过调整脉冲参数实现对授权频段的动态避让。仿真结果表明：自适应脉冲具有良好的窄带干扰抑制能力,能够自适应地随着感知结果动态地规避授权用户,从而实现UWB系统与其它通信系统的共存。     

基于Polycycle信号的干扰抑制UWB自适应脉冲设计

 针对认知超宽带与现存窄带系统干扰问题,采用Polycycle信号作为超宽带原始脉冲,使用Hermite矩阵特征向量方法设计了认知超宽带自适应脉冲,实现了干扰抑制.仿真结果表明,提出的自适应脉冲功率谱密度分布符合FCC室内和室外频谱规范,实现了自适应频段陷波.基于PAM-TH UWB系统性能分析表明自适应脉冲具有较强的多用户干扰和窄带干扰抑制能力.     

基于TH神经网络的UWB-SAR抑制RFI方法

在超宽带合成孔径雷达(UWB-SAR)系统中,若将接收信号先通过一个自适应预测误差滤波器,然后再进行成像处理运算,能极大改善其抑制射频干扰(RFI)能力.本文提出了一种迅速、有效的抑制RFI方法,它利用谱峰判阶并结合Tank-Hopfield(TH)神经网络计算滤波器权系数,在保持足够的抑制RFI能力的同时,大大提高了运算效率.     

基于认知无线电的脉冲陷波UWB窄带干扰抑制

提出了一种基于认知无线电的自适应超宽带(UWB)窄带干扰抑制方法.为了使UWB对变化的干扰环境具有自适应调节能力,引入了认知无线电技术.通过频谱感知和认知引擎技术提取窄带干扰频谱特征作为陷波器的设计依据.以高斯脉冲为例,对陷波器的陷波性能进行检验.最后,就陷波前、后脉冲的通信性能进行比较.仿真结果表明:认知陷波脉冲具有...     

一种基于加窗的窄带干扰抑制技术仿真与硬件实现

在简要总结窄带干扰抑制方案和技术的基础上,介绍了一种基于加窗的频域自适应窄带干扰抑制方法,该方法是在离散傅里叶变换(DFT)技术、自适应门限算法的基础上形成的,简单有效,可靠实用。软件仿真及硬件实测结果均证明了该方法的可行性及有效性。     

一种自适应直扩超宽带(DS-UWB)接收机在高速无线室内传输环境中的性能

该文提出了一种基于可变长训练序列的自适应直扩超宽带(DS-UWB)接收机。该接收机充分利用自适应NLMS算法在收敛性、复杂度及稳定性方面的综合优势,以较小的训练开销实现了自适应接收机的功能。理论分析及计算机仿真实验表明,在误码性能相当的前提下,所提出的自适应接收机比传统的Rake接收机具有更为简单的结构,同时与现有的自适应接收机相比,其训练序列的开销可节省60%以上,因而适用于低功率、低成本以及简易实用的室内超宽带应用场合。     

基于自适应多门限算法的变换域窄带干扰抑制

该文分析基于门限检测的直接序列扩频通信系统变换域窄带干扰抑制技术,提出一种基于自适应多门限窄带干扰抑制算法,并对其性能进行详细分析,理论分析和数字仿真结果表明,该算法可有效抑制直扩通信系统中的窄带干扰,并且相对于传统的门限检测算法,有自适应性强,门限设计简单等优点。     

一种抑制直扩通信窄带干扰的新型非线性自适应预测滤波器

为了更有效地抑制直接序列扩频通信中的窄带干扰,论文提出了一种非线性Laguerre滤波抑制直扩频通信窄带干扰的方法,给出相应的自适应算法。该方法利用具有IIR和FIR滤波器特点的Laguerre时延单元构造非线性自适应预测滤波器。该方法可以使预测器的记忆深度与预测器的阶数解偶,以更少的阶数达到更优的抑制性能。仿真实验结果表明:与Vijayan和Poor传统非线性自适应预测滤波器相比,该滤波器能够保证均方误差的收敛稳定性,并能在信噪比改善提高12dB的前提下,使滤波器阶数降低为原来的1/3~1/5,具有一定的现实意义。     

Adaptive Frequency-Domain Equalization with Narrowband Interference Suppression

Frequency-domain equalization (FDE) is an effective technique that exhibits the property of relatively low complexity which grows with increasing the number of symbols of dispersion in multipath propagation environments for broadband wireless communications compared with the conventional time-domain equalization. However, in practical broadband wireless communications, there exists not only multipath but also narrowband interference (NBI). The conventional FDE methods do not consider NBI and their performance degrades obviously in such case. In this paper, we propose a new optimization criterion which can effectively suppress NBI to obtain the maximum decision signal-to-noise ratio. The proposed scheme employs a conventional adaptive algorithm such as least-mean-square or recursive-least-square and operates in the spatial-frequency domain, which is concerned with the use of FDE and space diversity within block transmission schemes jointly. The simulation results show that the proposed schemes have better error-rate performance with low complexity and can be used even in the presence of strong NBI, compared to other existing adaptive FDE algorithms.     

M‐ary Bi‐orthogonal Modulation UWB with Narrowband Interference Suppression Capability

An M‐ary bi‐orthogonal modulation scheme for ultra‐wideband (UWB) systems capable of narrowband interference (NBI) suppression is proposed in this letter. We utilize a set of bi‐orthogonal pulse series to achieve NBI suppression. Through analysis and simulation, we verify that the proposed scheme can suppress NBIs effectively.     

EFFICIENT CYCLIC PREFIX RECONSTRUCTION USING DECISION FEEDBACK FILTER FOR CODED SINGLE-CARRIER SYSTEMS WITH FREQUENCY-DOMAIN EQUALIZATION （SC-FDE）

In this paper, an efficient Cyclic Prefix （CP） reconstruction scheme is proposed for Single-Carrier systems with Frequency-Domain Equalization （SC-FDE） that employ insufficient length of CP at the transmitter. By utilizing a decision feedback filter to cancel the residual InterSymbol Interference （ISI） in the equalized signal, the proposed scheme can effectively lower the low bound of performance for the CP reconstruction schemes and can greatly improve the Bit Error P~te （BER） performance of SC-FDE systems. In addition, the existing methods and the proposed scheme are also optimized. It is shown in the simulation results that, when the Signal-to-Noise Ratio （SNR） exceeds a certain threshold, the proposed scheme can achieve the low bound of performance for the existing methods. Moreover, by increasing the number of iteration or through optimization, the low bound can be outperformed.     

一种具有窄带干扰抑制能力的改进型LSL插值算法

本文提出了一种基于QR分解技术的最小二乘格形插值算法-QRD-LSL插值算法来抑制直扩系统中的窄带干扰.该算法利用直扩信号、噪声信号和窄带干扰信号数据样值间相关特性的差异,通过对直扩系统接收端数据样值序列进行插值运算来估计窄带干扰信号成分,从而达到抑制直扩系统中窄带干扰的目的.由于该算法引入了QR分解过程避免了对数据矩阵求逆运算,并引用动态范围较小的新变量参与阶递推运算,极大程度上提升了算法在稳态特征、收敛速度和计算复杂度等方面的性能.仿真结果表明:QRD-LSL插值算法较LSL插值算法和LSL预测算法至少可获得4dB的处理增益,且计算量与滤波阶数呈线性关系.     

Blind Adaptive Suppression of Narrowband Digital Interferers from Spread Spectrum Signals

The application of the minimum-mean-square-error (MMSE) multiuser detection technique to the problem of suppressing the digital narrowband interference (NBI) from spread-spectrum signals is considered. The MMSE multiuser detector can be implemented using a blind adaptive method, which is ideally suited for use in the NBI suppression framework. The optimal linear filter for the recovery of the spread-spectrum signal is derived, and its performance is analyzed in terms of probability of error and signal-to-interference ratio (SIR). It is shown that the performance of this optimal filter is very close to the situation when there is no narrowband interference present, even at the presense of very strong interference. This application requires the treatment of a single narrowband digital signal as a group of related, virtual spread-spectrum signals with very simple spreading codes. This model gives a special structure to the matrices appearing in the optimization problem implied by the MMSE criterion, and this structure is exploited herein to develop and analyze a practical adaptive algorithm. The major contribution of this paper beyond the previous work in the field of NBI suppression is the development of this adaptive algorithm that can exploit the advantages of multiuser detection in suppressing narrowband digital interference from spread-spectrum networks.     

直扩系统中IIR格型滤波器抑制窄带干扰新方法与性能分析

该文提出一种直扩系统中基于IIR格型陷波器时域频域相结合的窄带干扰抑制新方法,该方法采用时域频域并行处理的结构,通过最优加窗和频谱校正技术在频域精确估计出干扰信号的频率,根据频率估计误差和干信比求出最优陷波带宽,由此自适应地调整时域IIR格型陷波器的参数。分析和实验表明,该方法较传统的自适应IIR窄带干扰抑制方法不仅具有更高的稳定性和实时性,而且在干扰得到有效抑制的情况下使有用信号的损失达到最小。     

MMSE RAKE Reception for Asynchronous DS/CDMA Overlay Systems and Frequency-Selective Fading Channels

In this work the authors introduce and analyze a detection scheme for simultaneous suppression ofmultiaccess and digital narrowband interference (NBI) for an asynchronousDS/CDMA system operatingover a frequency-selective fading channel. The proposed detector may possibly consider a processing interval greater than the bit-interval, andamounts to a RAKE structure, wherein each branch is designed under an MMSE optimization strategy, followedby a propercombining rule. It is shown that narrowband interference rejection entails ingeneral a time-varyingdetection structure. As to the performance assessment, we give closed-form formulas for the systemBit Error Rate (BER),Near-Far Resistance and Signal-to-Interference Ratio (SIR).Numerical results show that the proposed receiver proves effective in suppressing interference, and that itlargely outperforms conventional multiuser detectors which do not account forthe presence of theNBI, at the price of little complexity increase.Finally, we provide a blind adaptive implementation of the proposedreceiver, based on the exponentially weighted Recursive-Least-Squares (RLS)algorithm, andrequiring knowledge of the relevant parameters of the desired user only, andof the NBI signaling time.     

基于压缩感知的窄带干扰重构与消除

提出了一种基于压缩感知的TDS-OFDM系统窄带干扰重构方法,通过利用相邻TDS-OFDM帧头的差分采样建立压缩感知模型,能够在不依赖信道估计及在高频谱效率的条件下,精确恢复窄带干扰信号并予以消除,显著提升传输系统传输鲁棒性。