一种CPM信号检测与定时同步算法

针对传统连续相位调制(CPM)接收机检测复杂度高和定时同步困难的问题,提出一种CPM信号联合检测与定时同步算法。基于低维Walsh信号空间分解CPM信号,在低通滤波器中采用子区间采样器代替大量匹配滤波器,利用面向判决的方式进行定时同步。仿真实验表明,该算法的复杂度较低,适用于多数CPM调制方案。     

球形译码算法在信号空间分集系统中的应用研究

针对信号空间分集系统中最大似然检测算法复杂度高的问题,选用球形译码算法作为信号空间分集系统接收机检测算法,可以使接收机在接近最大似然算法检测性能的同时,降低接收机检测复杂度。为进一步降低检测复杂度,通过采用最小均方误差算法减小噪声对接收信号的干扰,来降低因搜索噪声点而产生的复杂度,并利用衰减因子k加快搜索半径收缩来达到进一步降低球形译码算法检测复杂度的目的。仿真结果表明,在信号空间分集系统中引入球形译码算法可以降低接收机检测复杂度,并且改进后的球形译码算法检测时间在低信噪比情况下约为传统球形译码算法的12%—33%。因此,球形译码算法可以有效地降低信号空间分集系统接收机检测复杂度。     

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.     

北斗系统C频段导航信号的波形设计

在分析比较C频段和L频段信号传输特点的基础上,通过信号的兼容性、导航性能以及接收机实现复杂度约束条件的折中,提出基于椭圆球面波函数PSWF(Prolate Spheroidal Wave Functions)的C频段信号波形设计方案。仿真结果表明,基于PSWF的优化信号具有良好的带外抑制特性,满足C频段信号设计的严格兼容性约束要求,并具有优于传统BPSK调制的跟踪测距精度和抗多径性能。     

基于压缩信号处理的BOC信号解调

为了降低二进制偏移载波调制(BOC)信号的采样频率,提出一种基于压缩信号处理的BOC信号解调方案。采用该方法可以降低A/D的采样速率和系统功耗,并且硬件结构比其他方案更加简单。仿真实验表明,压缩感知可以成功地应用在BOC信号接收机中。受噪声折叠的影响,压缩信号处理BOC接收机的性能要比传统接收机略低,其优势在于降低实现的复杂度。考虑信号的量化,噪声折叠对接收机的性能影响要小得多。     

低复杂度的空间调制信号检测

空间调制(SM)算法在接收端常用最大释然(ML)信号检测获得发送天线编号以及调制符号,恢复发射信息比特,但是ML算法复杂度随着天线数和调制阶数的增加呈指数增长,不具有实用性。针对该难题,提出一种新的低复杂度次最优检测算法。通过设置合理的判决门限将信号矢量检测(SVD)和硬限最大似然(HL-ML)算法进行联合。蒙特卡洛仿真结果表明,该算法的误比特率检测性能比SVD算法更接近ML算法,且复杂度与ML算法相比降低了85%。     

2.4G直接下变频接收机射频前端的设计与研究

射频前端模块性能关系到整个接收机的性能,直接下变频接收机有体积小,价格低和高集成度的优点而受到了广泛的重视。本文对直接下变频接收机进行了研究,分析了该接收机特点,提出了一种直接下变频接收机的射频前端实现方案,并用软硬件平台对其实现,实测的2.4G本地振荡信号和接收机解调信号表明达到系统要求指标。     

无线电台监测仪的设计与实现

无线电是现代社会中有效的通信方式之一,运用无线电台监测具有很多监测方式不具备的优点。无线电台监测仪分两部分构成,分别是射频前端和数字中频接收机。射频前端先是捕获信号,并将它进行转换,使之成为宽带信号,经过数字接收机则对获取的信号进行处理,从而获得的需要的信息。文章针对无线电台监测仪的设计与监测原理进行了分析,通过系统测试对监测效果进行了判定。     

一种大规模MIMO系统中STBC迭代接收机算法

针对大规模MIMO中的空时分组编码(STBC)系统的接收机复杂度随天线数指数增长的问题,提出一种基于EM算法的低计算复杂度的最大似然(ML)接收机。利用STBC和OFMD调制的正交性,避免了矩阵求逆运算;采用步骤E与步骤M迭代处理的方式,极大降低接收机复杂度。基于信道特性提出EM算法初始化方法,达到减少迭代次数进而降低接收机复杂度和提升性能的目的。与之前的决策反馈的非迭代接收机相比,该迭代接收机性能显著提高,在具有快衰落的典型无线信道中,其计算复杂度接近ML接收机,适合实时实现。     

GPS接收机前端设计的要求及实现

从ＧＰＳ信号特点出发，对接收机前端设计要求进行了分析，并提出了实现方案，实验结果与设计性能完全一致，从而解决了ＧＰＳ接收机设计中射频（ＲＦ）前端的难点。     

基于Walsh变换的汉语非特定人语音识别的研究

运用Walsh变换对语音信号进行分析,得到了语音信号的Walsh域特征——2D自由度功率谱特征。利用此特征采用神经元网络法对汉语数字音0～9进行不定人语音识别,结果表明,该特征不仅能给出足够的识别信息,而且由于Walsh变换只有加/减运算,因而在识别速度方面比常用的频域特征有明显提高。     

Walsh transform theory and its application to systems analysis and control: an overview

The purpose of this paper is to provide an overview of the works dealing with the application and utilization of Walsh function series and transforms to a variety of systems and control applications. The works reviewed are classified in the following groups: 1. Walsh signal definition and generation, 2. Walsh transform Computation, 3. System analysis using Walsh functions, 4. System identification via Walsh functions, 5. Optimal control via Walsh functions, 6. Block-pulse functions, 7. Miscellaneous properties of Walsh functions, 8. Walsh-to-Fourier transform conversion, and 9. Walsh transform applications.     

On the Fourier transform of sequency limited signals with applications to delta modulation and medicine†

It is the binary nature of the Walsh basis functions that make the Walsh transform a potentially useful signal processing tool. Unlike the FFT, which produces a database in the easily interpreted frequency domain, a Walsh data base resides in the obscure sequency domain. Using a fast Walsh algorithm, an N-point transform can, however, be computed more rapidly than a FFT using a similar computer architecture. Even though the sequency space has been shown to be useful in coding and picture processing applications, the aperiodic behaviour of its basis functions make it. unsuitable for many traditional signal-processing problems. It would be desirable, for example, to be able to relate the computationally efficient Walsh spectra to the intuitively pleasing Fourier spectra. This work will address that problem and present new results.     

基于Walsh变换的谐波分析浆液型电磁流量计信号处理方法

针对浆液型电磁流量计的矩形波励磁技术,提出一种更加符合矩形波特点的Walsh变换法。对基于Walsh变换的谐波分析方法进行实验验证其可行性和实际效果。实验表明在不提升励磁频率的前提下,该谐波分析方法可以一定程度克服浆液噪声引起的流量信号波动。从而为浆液型电磁流量计的谐波分析方法提供了一种新的思路和理论依据。     

New enumeration of Walsh matrices

The discrete Walsh transform is a linear transform defined by a Walsh matrix. Three ways to construct Walsh matrices are known, which differ by the sequence order of rows and correspond to the Paley, Walsh, and Hadamard enumerations. We propose a new enumeration of Walsh matrices and study its properties. The new enumeration is constructed as a linear rearrangement; we obtain an eigenvector basis for it and propose a convenient-to-generate fast implementation algorithm; the new enumeration possesses certain symmetry properties, which make it similar to the discrete Fourier transform.     

Mechanic signal analysis based on the Haar-type orthogonal matrix

Between Haar and Walsh, there exist other Haar-type orthogonal matrixes (HTOMs), which are rarely utilized in practice. In this paper, we introduce HTOMs, which have fast algorithm, to the mechanic signal analysis. Concretely speaking, the mechanic signals are transformed by various HTOMs, which can be generated easily by varying any one of two parameters in the same program, then the performance of the transform results is compared by viewing FDC as the evaluation criterion, and the most optimal HTOM is achieved, which provides guidance and reference for the HTOMs applied in the signal analysis.     

ECG data compression using fast Walsh transform and its clinical acceptability

Data compression techniques can be grouped into three categories, direct and transformation compression and parameter extraction. The principles and details of ECG data compression implementation using fast Walsh transform are presented. Performance evaluation has been made on the basis of compression ratio and visual comparison. To know the extent to which the clinical information preserved in the reconstructed signal, peak and boundary measurements were made on both the reconstructed and original signal, and then compared. As the number of fast Walsh transform coefficients are reduced, the compression ratio increases. At higher compression ratios deviations in the R-peak are found to be higher than those in the other ECG peaks. Peak and boundary measurements reveal clinical acceptability of the compression algorithm, because the errors are quite tolerable. It is also worth noting that artefacts such as electromyographic noise are better eliminated because of filtering, and this also makes the signal compatible to cardiologists for visual examination. The experimental results show that a compression ratio of four is acceptable to preserve the clinical information.     

Dual purpose FWT domain spread spectrum image watermarking in real time

Spread spectrum (SS) watermarking for multimedia signal becomes appealing due to its high robustness attribute and is used widely for various applications. Some of these applications essentially demand development of low cost algorithms so that they can be used for real time services such as broadcast monitoring, security in communication etc. In recent time one popular non-conventional application of digital watermarking becomes promising that assesses blindly the QoS (quality of services) of the multimedia services which is expected to be offered by the future generation mobile radio network. Majority of the existing SS watermarking schemes suffer from high computation cost and complexity leading to the difficulty for real time implementation and limits their usage for the above mentioned applications. This paper proposes fast Walsh transform (FWT) based SS image watermarking scheme that serves the dual purposes of authentication in data transmission as well as QoS assessment for digital media through dynamic estimation of the wireless channel condition. Fast Walsh transform offers low computation cost for implementation, smaller change in image (multimedia signal) information due to data embedding and ease of hardware realization. VLSI implementation using field programmable gate array (FPGA) has been developed to make it suitable for real time implementation.     

Sampling principle for duration-limited signals and dyadic Walsh analysis

A sampling theorem based on Walsh analysis techniques for not necessarily sequency-limited signals is constructed. By using the concept of the so-called dyadic derivative, the authors calculate the error that arises when only a finite number of samples of a signal with discrete values is chosen.     

软判决快速相关攻击新算法与应用

近年来,密码的快速相关攻击(FCA)是一个研究热点.由于采用了一系列纠错编码的译码新技术,使得该问题的研究取得了很大的进展.但如何使这些新技术充分地适应具体的密钥序列的攻击依然是一个公开的研究课题.首先把模2域上的FCA算法推广成软判决快速相关攻击(SFCA)算法,并给出了如何根据信道信噪比情况配置最佳的参数的方法.实验表明,在BPSK调制下,SFCA算法比FCA算法有2dB以上的增益.作为SFCA算法的应用,给出了实现扩频通信中的m序列的快速同步捕获的新方法.与最近Yang(2004)提出的RSSE方法比较,新方法无论是捕获性能还是捕获速度都有了大幅度地提升,而且在低信噪比通信情况下,同步捕获所需的码片数只是RSSE方法所需的码片数的1/20.