超宽带通信系统的Simulink仿真实现

超宽带(UWB)脉冲无线电(IR)技术是一个新兴的通信技术,具有诸多的优点,正受到人们越来越广泛的关注。Simulink是一种用来建模、仿真和分析动态系统的集成仿真工具：该文介绍了超宽带脉冲无线电和Simulink的特点,在Simulink环境下搭建并实现了超宽带通信系统的仿真。提出了在跳时(TH)脉冲位置调制(PPM)通信系统中的同步相关算法,主要对仿真链路中的接收机进行设计和实现,其中包括信号检测、伪随机序列捕获、数据同步等。结果表明,该仿真系统在超宽带通信中是可行的。     

基于抑制噪声干扰的ATR-UWB接收机

分析了超宽带接收机的原理和特点,着重对能够有效抑制噪声干扰的ATR-UWB(Average Transmitted Reference Ultra-Wideband)接收机进行了详细的分析推导,给出了ATR-UWB接收机的误码性能表达式。进一步对几种常见的超宽带接收机在多径信道叠加高斯白噪声下的误码率性能进行分析和比较,并进行了性能仿真。仿真结果表明,在低复杂度的条件下,抑制噪声干扰的ATR-UWB接收机具有良好的性能。     

一种基于边沿/门限检测的IR-UWB接收方法

针对脉冲无线电超宽带(Impulse Radio-Ultrawide Band,IR-UWB)无线通信接收机定时精度要求高、结构复杂等问题,提出了一种基于边沿/门限检测(Edge/Threshold Detection)的非相干IR-UWB接收方法.该接收方法利用了IR系统脉冲波形占空比低的特点,将窄脉冲展宽为宽脉冲,降低了定时要求,实现结构较简单.对该接收方法进行了理论分析,给出了加性高斯白噪声(AWGN)信道环境下、OOK调制的误码特性及仿真结果.结果表明接收方法性能主要取决于接收采样时钟频率,当采样时钟频率较高时,该接收方法性能与有20ps定时抖动的相干接收性能可比拟.     

超宽带传输参考接收机研究

针对超宽带传输参考接收机模板信号包含噪声的问题,引入了一种新型的超宽带传输参考接收机结构,重点分析了该接收机的原理及性能。通过仿真验证,该新型的超宽带传输参考接收机性能相比平均超宽带传输参考接收机有很大提升。     

取样脉冲对平衡式取样积分微分电路性能影响

取样脉冲是影响超宽带无线电引信接收机性能的关键因素。在分析取样积分微分电路工作原理的基础上,建立了其频域和时域数学模型。结合无载波信号的时域多普勒效应,提出了基于Matlab的超宽带无线电引信接收机输出信号时域仿真方法。研究了取样脉冲宽度和幅度对电路输出波形的影响,结果表明:电路完全对称时,输出信号幅度只与取样脉冲宽度有关,但并非单调关系;非对称时,电路达到稳态前产生一个脉冲信号,脉冲幅度与取样脉冲的幅度成正比,宽度成反比。     

一种简易的超宽带脉冲信号产生电路设计

介绍了一种只利用单一微波三极管作为电路核心来产生超宽带脉冲的简单电路。通过仿真该电路可以产生重复频率1M Hz ,幅值将近4V ,脉宽1ns的负极性高斯脉冲。测试结果表明该电路可以产生超宽带发射技术所要求的脉冲。通过比较几种超宽带信号产生技术,该电路产生的冲激脉冲幅值更大、成本低、结构简单、工程性强。     

超宽带Pre—Rake接收技术研究

针对当前超宽带系统接收机误码性能较低、复杂度较高的缺点,提出了一种采用DS-PAM调制的Pre-Rake分集合并接收方案.方案基于IEEE802.15.3a的超宽带标准信道模型,首先将DS-PAM调制的发送信号,经信道传输后,在接收端对最强径信号做采样判决.基于蒙特卡罗仿真,对Pre-Arake、Pre-Stake、Pre-Prake等三种不同结构和不同支路数下的接收机性能进行了分析,并比较了不同脉冲传输速率和不同信道环境下的Pre-Rake接收机和Rake接收机的误码率.仿真结果表明,在传输速率较高且多径衰落严重的信道环境里,Pre-Rake接收机的误码率明显低于传统的Rake接收机,即Pre-Rake接收机可以有效的克服码间干扰和多径衰落.     

基于希尔伯特-黄和小波包的UWB信号检测方法

针对希尔伯特-黄变换在超宽带脉冲检测中检测性能受限于信噪比的问题,研究并分析了筛选终止条件以及小波包去噪方法,结合新终止条件,给出了希尔伯特-黄变换与小波包分析联合检测的新方法。采用新方法对噪声中的超宽带信号进行检测分析,并运用均方根误差公式对该方法的检测性能进行仿真比较。仿真图表明,新方法能较为准确地重构出淹没在强噪声下的脉冲,成功克服HHT变换在检测超宽带脉冲时受噪声强度影响较大的问题,从而改善强噪声环境下脉冲信号的检测效果。     

水下窄脉冲超宽带信号的传播特性仿真

超宽带信号具有分辨率高、截获概率低、穿透能力强等优点,将在水下目标探测、定位及通信等领域具有良好的应用前景;基于水下等离子体声源提出了窄脉冲超宽带信号产生方法,建立了以传播损失和海洋环境噪声为主要影响因素的超宽带脉冲传播信道模型;结合湖试实测数据,利用Matlab仿真软件和Welch谱分析法,仿真分析了不同频率的超宽带脉冲在水下传播不同距离后的功率谱密度以及传播特性;研究成果对水下等离子体超宽带脉冲的工程应用具有重要的参考价值,同时对水下等离子体超宽带脉冲声源的设计和研制也有一定的借鉴意义.     

脉冲噪声中基于广义恒模算法的多用户检测

在高斯白噪声信道中提出的各种多用户检测方法在脉冲噪声存在的情况下出现了明显的质量下降,而实际的物理信道中又经常伴随着脉冲噪声。将α-稳定分布噪声作为背景噪声模拟实际物理信道中存在的脉冲噪声,根据脉冲噪声的特殊性质,在恒模多用户检测算法的基础上将广义恒模算法应用到了多用户检测技术中去。仿真结果表明该算法在高斯白噪声以及α-稳定分布的脉冲噪声中均取得的良好的性能,具有很好的鲁棒性。     

利用训练序列进行无线信道响应的低价估计

蜂窝CDMA移动通信系统接收机中的最优信号处理需要通过嵌在发射信号中的训练信号来估计实际信道的冲激响应。在CDMA移动通信系统中上行信道的许多估计方法虽然有很多优点但是成本很高。本文提出并分析了一种信道估计方法，其中所有用户的不同训练信号由同一基本信号的不同移位构成。因此实现了一个相关器形式的低成本信道估计器．     

A novel low complexity data demodulation algorithm for pulse position modulation

In this paper, a low complexity data demodulation algorithm is proposed that requires time of arrival information of the received signal exclusively. As an application example, the algorithm is applied to an ultra-wideband impulse radio communication system with pulse position modulation. The algorithm is insensitive to a common time delay for all pulses, that means, it does not require an accurate synchronization between the transmitter and the receiver. For the performance estimation, only a symbol synchronization is assumed, i.e., that there is a priori knowledge which pulse marks the beginning of a received data symbol. The performance of the proposed algorithm is evaluated for straightforward time of arrivals estimators, such as a maximum detector or a threshold detector. It is shown that the proposed algorithm outperforms a least squares algorithm in all considered scenarios. In particular, an increased robustness against additive white Gaussian noise, impulse like noise, and multiuser interference is demonstrated as well as an improved performance for multipath propagation channels.     

一种基于振幅比较的UWB信号解调方法

无传统意义上的载波带来的低复杂度特性是脉冲无线电超宽带(ultra widcband, UWB)通信的一大优势,既有较佳的接收性能又有简单的结构是UWI3系统设计的目标。提出了一种基于振幅比较的UWI3信号接收的解调方法,即在脉冲位置调制中的特定位置,分别对脉冲的正负半周积分获得振幅信息,并通过比较这些振幅解调出符号信息。该方法能够在接收性能和系统复杂性之间获得较好的平衡。结果表明,它以较小的复杂性代价换取了比平方律检测好5 dI3以上的误码性能;而与相关检测相比,误码性能约降低了2 dI3,但复杂度低于相关检测。     

超宽带信号功率谱的仿真分析

超宽带(UWB)信号及其功率谱分布是研究超宽带通信系统与其它通信系统频谱共存与兼容问题时,需要考虑的重要因素.根据超宽带信号功率谱的特点,从控制超宽带信号功率谱分布的角度,就高斯单周期脉冲及其各阶导函数、不同的信息调制方式和跳时码参数对超宽带信号功率谱的影响,进行了计算机仿真和分析,并总结出控制超宽带信号功率谱分布的方法,从而为解决超宽带通信系统与其他通信系统频谱共存问题,提供了有益的思想和方法.     

Averaging and oversampling correlator receiver with input quantization

Correlation is a fundamental technique to detect signals buried in noise. However, due to noise, the fluctuations of the output signal may be significant and the detection of the desired signal can then fail. It is known that a simple one-bit correlator receiver can give nearly identical performance to the full precision correlator in determining time delays in medium signal-to-noise ratio situations, when averaging several successive correlation signals. An oversampled and averaged version of the correlator, with input quantization to a low number of bits, is studied here using simulation. It is demonstrated that, by oversampling the received signal at a multiple of the correlation code clock rate and averaging over several successive samples, performance similar to that of the full precision correlator may be attained to in low SNR situations.     

Bit error rate reduction for circular ultrawideband antenna by dynamic differential evolution

The dynamic differential evolution (DDE) is used to synthesize the radiation pattern of the directional circular arc array to minimize the bit error rate (BER) performance in indoor ultrawideband (UWB) communication system. Using the impulse response of multipath channel, the BER performance of the synthesized antenna pattern on binary pulse amplitude modulation system can be calculated. Based on the topography of the circular antenna array and the BER formula, the array pattern synthesis problem can be reformulated into an optimization problem and solved by the DDE algorithm. The novelties of our approach are not only choosing BER as the object function instead of sidelobe level of the antenna pattern but also considering the antenna feed length effect of each array element. The strong point of the DDE algorithm is that it can find out the solution even if the performance index cannot be formulated by simple equations. Simulation results show that the synthesized antenna array pattern is effective to focus maximum gain to the line of site path which scales as the number of array elements. In other words, the receiver can increase the received signal energy to noise ratio. The synthesized array pattern also can mitigate severe multipath fading in complex propagation environment. As a result, the BER can be reduced substantially in indoor UWB communication system. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Wavelet-based spectral shaping of UWB radio signal for multisystem coexistence

Although Ultra Wide Band (UWB) wireless systems supposed to coexist with other spectrally overlapping (narrowband) wireless systems, mutual interference degrades the performance of both systems. In this paper we investigate two techniques for reducing this mutual interference which do not require modification of the narrowband system. We propose to shape the spectrum of the Transmitted Reference (TR)-UWB signal using wavelet based multi-resolution technique to avoid its interference to other wireless systems. The reverse (narrowband) interference is alleviated using a notch filter at UWB receiver that could have much smaller bandwidth in this Gaussian pulse-shaped multi-resolution environment. TR simulations under AWGN and multipath channel conditions show that up to 55 dB reduction of UWB RF energy is possible at the interfering IEEE 802.11a band using the wavelet spectral shaping technique. The challenge is not to exceed the specified pulse duration while shaping the spectrum. The proposed technique does not reduce the throughput of the UWB system. It is general in the sense, it can be used for the better coexistence of any narrowband wireless system with UWB system.     

基于ML准则的UWB信号同步捕获方法*

为了在超宽带通信系统中,简单、快速地实现信号的同步捕获和信道估计,提出一种首先利用相关器粗略估计出有用信号的起始位置,然后采用最大似然估计准则实现同步捕获和信道估计的分步同步捕获方法.该方法既提高了估计精度,又有效降低了接收机的复杂度和处理时间.     

重叠与正交脉冲信号下的UWB系统性能研究

介绍了TH-UWB信号模型,推导出了在AWGN信道条件和多径条件下,重叠和正交脉冲信号下的TH-BPPMUWB系统的误码率公式,并进行了仿真。仿真结果表明在AWGN信道条件下,基于重叠脉冲信号的TH-BPPM系统性能优于基于正交脉冲信号的TH-BPPM;多径条件下的正交TH-BPPM的系统性能优于AWGN信道条件下的系统性能。     

冲击体制雷达动目标积累算法及其应用

为了对超宽带动目标进行有效检测,对其回波的特点进行了分析,在此基础上提出了新颖的基于峰值对匹配的积累算法;设计了一套由功率合成的全固态脉冲发射机、超宽带平面喇叭收发天线阵、正交解调采样接收机、主控计算机四大部分组成的冲击体制雷达目标探测系统,介绍了系统的工作原理;该算法应用于实际系统之中,目标回波在距离门中位置保持稳定,并在积累过程中保持原有的形状,幅度随累加次数增加而增大,这表明了该方法的有效性.