用于UHF RFID的自动调节泄漏载波抵消电路

用于UHF RFID的自动调节泄漏载波抵消电路采用功率反射相消技术和近似最速下降法的自动调节算法,主要解决UHF RFID读写器收发机载波泄漏问题。调节过程由FPGA控制,采用近似最速下降法,能够在100ms左右完成调节过程。通过本电路的泄漏载波抵消,UHF RFID收发机的隔离度可以在较宽的频带内达到60dB以上,峰值可以达到70dB。     

射频识别系统中的防冲突算法研究

在射频识别(Radio Frequency Identification,简称RFID)系统工作时,可能会有多个电子标签同时处于读写器的作用范围内,如果有两个或两个以上的电子标签同时向读写器发送数据,则会出现通信冲突或数据相互干扰.在读写器的接收器中,若不能正确识别电子标签的数据包,系统就会产生错误.为了防止RFID系统中多个电子标签同时向读写器发送识别信息产生冲突问题,从射频识别系统中防冲突算法的原理出发,研究了二进制搜索算法.结合动态二进制搜索算法的改进思路,提出了一种改良型动态二进制搜索算法.     

射频自适应干扰抵消系统的分析与设计

自适应干扰抵消系统对提高电子对抗装备性能有非常重要的意义。在对自适应抵消系统原理模型进行总体分析的基础上,提出了系统的射频实现方案并对方案的性能做了详细的分析。针对工程实现过程中的一些问题进行了讨论,并给出了一些解决方法。依据该方案在225~400 MHz的工作频段内设计完成了性能较好的自适应干扰抵消系统,系统窄带抵消比接近50 dB,抵消时间小于1 ms,并且在整个工作频段内性能稳定可靠。     

一种应用于超高频RFID的自干扰抵消电路

提出了一种应用于超高频RFID的集成自干扰抵消电路,它主要由一个6位有源移相器、一个3位可控增益功率放大器和缓冲器组成。有源移相器采用可降位的编码方式,简化了数字逻辑。可控增益功率放大器通过采用电容补偿技术和偏置点的优化选取来提高线性度。该自干扰抵消电路在130 nm CMOS工艺下实现,采用1.5 V和3.3 V双电源供电。后仿真结果显示,针对8 dBm的自干扰信号,该电路在840~940 MHz带宽内的自干扰抑制比大于28 dB。     

超高频射频识别标签和阅读器产品测试平台

RFID是射频识别技术的英文（Radio Frequency Identification）缩写,射频识别技术是自动识别技术的一种,是一项利用射频信号通过空间耦合（交变磁场或电磁场）实现无接触信息传递并通过所传递的信息达到识别目的的技术。射频识别系统通常由电子标签（射频标签）和阅读器组成。     

同时同频全双工场景中的射频域自适应干扰抵消

考虑同时同频全双工无线收发信机的射频域自干扰抵消技术,现有研究多集中于利用手动方式调整自干扰估计信号的参数。针对这一问题,该文提出一种射频域的自适应干扰抵消算法。以正交、同相参考支路构成的自干扰估计结构为基础,利用梯度下降法搜索支路的最优权矢量,估计出自干扰信号,实现了射频域的自适应干扰抵消,并且给出了该算法的收敛性分析。分析与仿真表明,当迭代步长越大或统计时间越短时,算法的收敛速度越小。在100倍符号周期的统计时间,0.3的归一化步长,80 dB干信比以及0 dB信噪比的仿真条件下,该文提出的射频域自适应干扰抵消算法可以实现约100 dB的自干扰抑制。     

一种适用于RFID阅读器的新型自动增益调节电路

为了提高射频识别(RFID)阅读器中接收机的动态范围,并实现对贴有标签目标物体的跟踪,在分析传统自动增益控制模块的基础上,设计了一种适用于RFID接收机的大动态范围自动增益调整电路,电路结构简单.基于ADS软件的仿真结果表明:该电路能够根据输入信号的功率水平自动地调整其增益,输入动态范围高达80 dB,自动增益调节范围...     

UHF RFID阅读器中的堆叠式CMOS LNA设计

提出了一种基于0.25μm标准CMOS工艺,可用于UHF RFID（超高频射频识别）阅读器前端的低噪声放大器。根据低噪声放大器的匹配、噪声和增益分析,结合射频识别系统的理论计算,提出堆叠器件的电路结构达到电流复用,以降低功耗并保证增益。测试结果表明,在2.5 V供电时,放大器可以提供约26.3 dB的前向增益,噪声系数约为1.9 dB,放大电路从电源电压上抽取5.8 mA左右的工作电流,反向隔离度达到-40 dB,放大器的IIP3约为-15 dBm。     

射频识别技术

射频识别,即RFID(Radio Frequency IDentification)技术,又称电子标签、无线射频识别,是一种非接触式的自动识别技术,它通过射频信号自动识别目标对象并获取相关数据,识别工作无需人工干预,可工作于各种恶劣环境。RFID技术可识别高速运动物体并可同时识别多个标签,操作快捷方便。RFID是一种简单的无线系统,只有两个基本器件,该系统用于控制、检测和跟踪物体。系统由一个询问器(或阅读器)和很多应答器(或标签)组成。     

一种SAW RFID阅读器的信号处理电路设计

为适应复杂环境中RFID系统的使用,基于SAW标签的RFID系统弥补了传统基于IC标签的RFID系统易受环境干扰等缺点。介绍了识别SAW标签的RFID阅读器的系统设计方案,详细说明阅读器信号处理电路的设计过程,通过软件仿真与电路调试,验证了基于C8051F的SAW RFID阅读器设计可行性。信号处理电路具有结构简单,成本低廉等特点,有较好的应用价值。     

Multistage Nonlinear Blind Interference Cancellation for DS-CDMA Systems

In this paper we propose a multistage nonlinear blind interference cancellation (MS-NL-BIC) receiver for direct-sequence code-division multiple-access (DS-CDMA) systems. The receiver uses higher order statistics of the received baseband signal. Specifically, we use the second and fourth moments of the received signal to determine a component of the received vector that has significant mean energy and low variability of the energy, both of which are favorable characteristics for application in an interference cancellation scheme that uses hard decisions. The structure of the receiver is multidimensional and can be viewed as a matrix of receivers. Each row in the matrix consists of receivers that perform (hard decisions) cancellation of successive components that have significant mean energy and low variability of the energy. The columns of the matrix essentially resemble multistage receivers that iteratively refine performance from earlier stages. Simulation results show that unlike linear receivers, the MS-NL-BIC is exceptionally efficient in systems with strong and highly correlated interferers, as may be the case in overloaded DS-CDMA systems.     

一种低复杂性的自适应干扰消除接收机方案

本文提出一种适用于码分多址系统的低复杂度自适应干扰消除接收机。 在此接收机中，我们首先基于第i个用户的第m个比特的输出引入一组可靠度因子 ，然后根据这组可靠度因子估算出多址干扰，最后通过执行干扰消除可得到符号判决值。通过在加性高斯白噪声信道和多径衰落信道中进行仿真。结果表明，本文提出的这种接收机方案的性能优越于传统检测器和一些已经存在的干扰消除算法，同时保持有较低的算法复杂度。     

Performance Analysis of DS Signal Code Acquisition Using the Matched Filter and the Median Filter

The theoretical analysis and simulation of the performance of a matched filter code acquisition structure with a median filter as the aiding device to cancel CW jamming in the AWGN channel is described. Both coherent and noncoherent structures are considered. As performance measures, the probability of detection and of a false alarm and mean acquisition times are used. Two kinds of analysis for coherent acquisition structure are presented. At first, the approximation for the pdf of the input signal to the comparator is used. Next, the probabilities are calculated directly. This is called the direct form. For the analysis of noncoherent acquisition, the pdf approximation of the coherent case is used. The performance of the median filter structure is compared to the performance of a simple linear interference cancellation method. The effect of CW jamming can be eliminated by both methods. Fixed thresholds of the comparator and the constant false alarm probability (CFAR) criteria are used. It is concluded that the median filter has a better performance, especially when fixed thresholds are used.     

适用于多载波共频谱传输的干扰消除方式

针对多载波共频谱传输应急卫星通信系统,各干扰载波互不相关,且干扰载波的功率远大于扩频信号的功率,干扰载波对扩频信号存在严重的干扰,因此对于扩频信号的恢复,载波重构与干扰消除处理是必须的。对于多载波干扰消除其实现方式可分为串行干扰消除和并行干扰消除2种,为此分析和比较了2种典型实现方式,提出了基于数字重采样的改进方案。分析结果表明,基于数字重采样的串行干扰方式更适合多载波共频谱传输应急系统卫星通信系统的应用。     

自适应算法在干扰抵消器应用中的比较研究

文中介绍了自适应滤波算法的原理和干扰抵消器工作原理，并将LMS算法、NLMS算法和变步长LMS算法分别应用在了干扰抵消器中进行了仿真。仿真的结果表明，三种自适应算法运用到了干扰抵消器中，都可以很好地滤除干扰，提取有用信号。其中运用了变步长LMS算法的干扰抵消器无论在收敛速度和滤波性能上，都要强于其他两种算法。     

宽带干扰信号自适应副瓣相消的分析

依据自适应副瓣相消的原理，着重分析了相对带宽较宽的干扰对副瓣相消性能的影响，提出了改善带宽特性的方法，进行了仿真验证。改善带宽特性的方法包括增加更多的辅助阵元，在阵元后面加入延迟节，利用快速傅里叶变换(FFT)等。     

宽带干扰信号自适应旁瓣相消性能分析及硬件实现

在自适应旁瓣相消技术中,天线的相消增益会随着信号带宽的增加而迅速下降.本文着重分析了利用加延迟线来解决这一问题的方法,对延迟线数目的选取进行了分析和仿真,并利用高速实时信号处理芯片ADSP-TS201实现了具体方案.     

Iterative QR Detection for BLAST

We study an iterative detection algorithm of an uncoded multi-transmittermulti-receiver system. The main data stream is demultiplexed into Msubstreams, and each substream is modulated independently then transmitted byits dedicated antenna. The receiver disposes of N M antennas. Over eachreceive antenna the signal is a superposition of the M substreams affected byindependent fades and disturbed by AWGN. The detection algorithm is based onthe QR decomposition of the channel transfer matrix which is then used toperform hard or soft inter-substream interference cancellation. Comparisonsare done with the V-BLAST optimal order (OPT) detection algorithm. Theproposed algorithm is 4 to 8 times less complex than that of the V-BLAST OPT,while maintaining comparable performance.     

Soft interference cancellation in multiuser communications

In this paper the performance of soft interference cancellation in synchronous multiuser channels is investigated. Two-stage detection with decorrelator in the first stage is considered. Soft first stage tentative decisions are formed by means of a multilevel quantizer or linear clipper. The asymptotic multiuser efficiency (AME) is used as a performance measured for optimization of the nonlinearity. It is shown, for the two-user case, that soft interference cancellation by means of an optimized linear clipper achieves the AME of the maximum likelihood detector if the crosscorrelation of the signature waveforms is less than . For the K-user case, novel upper bounds on the AME for two-stage detectors with feedback interference cancellation, with both hard and soft tentative decisions, are obtained. The derived bounds are used to examine the performance of two-stage detectors in a cellular scenario.     

高频地波雷达不同干扰抑制方法性能比较

在拥挤的高频波段,高频地波雷达受短波电台的影响而不能正常地进行工作,空域波束形成和基于水平天线辅助旁瓣对消的干扰抑制方法被用来对消此类电台干扰.比较了基于不同辅助天线以及不同信号处理顺序情况下的干扰抑制性能,对实测数据处理结果表明,基于水平辅助天线的方法能够在保证目标信息不丢失的情况下抑制主瓣干扰,距离域旁瓣对消的方法表现出最佳的干扰抑制性能.