复Q谱与正交蝶变换

本文引进复Q谱新概念.论证:序列U变换的复Q谱是循环位移不变量;序列的IT 1阶复Q谱与其循环自相关互为正交蝶变换.考察广义哈达玛变换与广义富里叶变换复Q谱属性与算法.简介复Q谱的应用. 复Q谱是信号分析的又一有用工具;它将为信号处理开拓新的研究前景.     

基于变换域的IMS信号处理方法及其改进

讨论了一种基于变换域的离子迁移谱(IMS)信号处理方法-傅立叶变换离子迁移谱(FT-IMS)技术,通过离子门开关频率的改变实现信号的调制,得到频域的IMS信号.该技术使离子利用率由百分之一提高到了百分之二十五,信噪比(SNR)提高了14 dB以上;通过增加离子门开关频率的范围可以进一步提高分辨率,解决了IMS技术中SNR和分辨率相矛盾的问题.在此基础上,改进了FT-IMS算法,减弱了FT-IMS技术中镜像脉冲的干扰.经对FT-IMS算法和改进算法的数值仿真验证,证明了其有效性.     

关于修改的沃尔什-哈达玛(W-H)变换的特点及其推广

本文首先引入桥函数的概念,然后讨论桥函数与修改的沃尔什-哈达玛变换之间的关系,从而说明修改的W-H变换构造的物理本质。在此基础上,引入了另一种修改的沃尔什-哈达玛变换方阵,并建立了相应的快速算法。     

哈达玛变换光谱仪

1.引言 哈达玛变换光谱仪是一个通过光学调制过程来获取光谱信息的装置。因为使用了色散系统,因此将常规的单狭缝出射模板代以按哈达玛矩阵循环码刻制的多条缝模板,它是一种色散光谱调制器,其结构示见图1。     

哈达玛变换成像光谱仪中光谱混合像素点的解码方法

介绍了一种基于DMD的哈达玛变换成像光谱仪的物理模型,由于DMD微镜单元尺寸与探测器像元尺寸不匹配或者其他一些在光学设计和系统集成中的误差,导致这种光谱仪中采集到的编码图像上部分像素点出现的一种光谱混合现象。描述和分析了这些光谱混合像素点的编码原理,分析表明:这种光谱混合像素点无法直接用哈达玛反变换解码。为了准确地解码这些光谱混合像素点,改善复原后光谱图像的质量,提出了一种针对这种光谱混合像素点的解码方法。首先向光谱仪中导入一束激光并充满整个视场,针对编码图像中的光谱混合像素点确定一个解码系数。然后将这个系数带入光谱混合像素点的编码方程,即可解码它的光谱元。实验结果证明该方法是可行的。     

用快速哈达玛变换加速滤波反投影算法的滤波过程

为了加速滤波反投影算法的滤波过程,提出了用快速哈达玛变换(FHT)实现线性卷积的快速算法。分析了哈达玛变换的特点和快速算法的时间复杂度,设计了用FHT计算线性卷积的矩阵表达式,并推导出了哈达玛域滤波器的增益矩阵的求解公式,分析了该方法的加速原理及其适用条件。理论分析表明,该方法比FFT线性卷积法快了一倍。仿真实验表明,该方法在不影响图像重建精度的情况下,相对于FFT线性卷积法,将滤波过程的速度提高了近一倍。     

基于沃尔什-哈达玛变换和卷积编码的半脆弱水印算法

提出了一种基于沃尔什-哈达玛变换和卷积编码的半脆弱水印算法.在该算法中,对嵌入水印之前的图像进行像素块差分编码和卷积纠错编码来得到水印,并将其嵌入在沃尔什-哈达玛变换的图像能量值上;水印检测端通过检测卷积译码中产生的误码实现水印篡改定位,利用卷积译码的结果实现篡改图像的恢复.通过理论和实验分析了该算法的有效性和由此产生的误差.实验结果表明,本算法对于有损压缩具有良好的顽健性,可以精确地检测与定位篡改的图像区域,并且可以大致恢复原始图像内容.     

DMD编码哈达玛变换高灵敏成像

为了增强探测器在微弱光信号条件下的成像质量,提出了一种利用哈达玛变换(Hadamard Transform,HT)实现高灵敏探测的成像方法。基于探测器噪声独立于信号,且每次测量噪声也相互独立的假设,分析了在哈达玛编码成像与经典成像中,噪声对图像信噪比的影响。推导出编码成像的信噪比提升与编码模板长度n有关,约为经典成像信噪比的n/2 倍。同时采用分区编码的方式,减小了高分辨率图像的编码时间。实验结果表明,与经典成像方式相比,采用分区编码的哈达玛变换成像方法明显的提高了图像的信噪比,同时可以在高分辨率图像条件下,缩短编码时间。     

基于多维扩展的正交时序复用波形框架及其性能分析

正交时序复用(OTSM)是一种适用于高速移动场景的低复杂度调制方法。然而,单一的波形设计方法难以满足多样化的应用需求和性能需求。因此,该文基于加权分数傅里叶变换(WFRFT)提出了加权分数沃尔什-哈达玛变换(WFRWHT),并提出了多维扩展的一体化的加权分数傅里叶变换-加权分数沃尔什哈达玛变换-正交时序复用(WFRFT-WFRWHT-OTSM)波形框架。通过对2维参数的灵活配置,该框架可退化为OTSM、正交时频空、混合载波、正交频分复用和单载波等波形,同时研究了采用高斯-赛德尔(GS)迭代均衡时一体化WFRFTWFRWHT-OTSM波形在时延-多普勒信道下的误码率(BER)性能以及峰均功率比(PAPR)性能。仿真结果表明,在不同时延-多普勒信道下,该框架可通过改变WFRFT和WFRWHT阶次实现更优的BER和PAPR性能。     

哈达玛变换光谱仪压缩系统研究

基于数字微镜器件（Digital Micro-mirror Device,DMD）的哈达玛变换光谱技术是一种新型的光谱成像技术,在国内很少有专门的文献介绍[1-3]。文中先介绍了本实验采用的哈达玛光谱仪样机的原理以及哈达玛成像光谱仪优于传统模板的独特之处,即获得多通道高能量高信噪比的光谱数据,然后描述对采集到的数据做高信噪比,高分辨率压缩处理,最后说明此方法实时性强、图像失真小、实用价值高、应用范围广。     

Hadamard变换离子迁移谱的理论模拟初步研究

通过改变采样点数，理论优化了Hadamard变换离子迁移谱（Hadamard transform ion mobility spectrometry, HT-IMS）谱图的采样速率；通过增加模拟的白噪声，分析了该方法提高谱图信噪比的效果和对分辨率的影响。初步结果表明，在单次离子门门宽0.4ms内，采集8个及以上数据点可以完整地反演IMS谱图；Hadamard变换方法得到的谱图的信噪比是传统IMS谱图信噪比的15.8倍，是相同时间内多次传统IMS谱图平均后信噪比的4.6倍；变换过程对IMS谱图分辨率无明显影响。Hadamard变换IMS的模拟不仅对采样速率等参数的选择和优化提供理论依据，而且为下一步实验控制和反演奠定软件基础。     

FSD技术在IMS信号处理中的应用

傅里叶自去卷积(FSD)目前已经成为较为常用的重叠峰解析技术之一,FSD在离子迁移谱(IMS)信号处理中的应用技术,通过对采集信号的去卷积提高IMS信号的分辨率,但是在其应用中也存在着线性函数宽度选择难度大、线性函数跟实际系统存在差异、造成实际信号的失真等问题,针对FSD存在的问题,提出了一种新的线性函数选择方法,解决了FSD技术线性函数不易选择的问题,去除了IMS系统对IMS信号的影响,提高了IMS信号的分辨率。通过试验验证了该方法的有效性。     

短波红外Hadmard变换高光谱成像技术研究

Hadmard变换成像光谱技术基于Hadmard变换光学基本原理,采用线阵探测器件实现高光谱成像,多通道探测优势使其在一定条件下可以获得与推帚式高光谱成像相当水平的探测信噪比.本文在阐述Hadmard变换成像光谱技术基本原理的基础上,通过类比光机扫描成像和推帚式成像,论证了Hadmard变换成像光谱技术的探测信噪比优势,设计了一套基于线阵短波红外器件、DMD芯片和双Offner光栅光谱仪系统的高光谱成像光谱仪,并简要论证了其工程可行性.     

BER Performance of Walsh–Hadamard Like Kronecker Product Codes in a DS-CDMA and Cognitive Underlay System

Walsh–Hadamard transform, a discrete unitary transform is widely used in many applications such as signature codes in the current wireless standards IS-95 CDMA, WCDMA, CDMA2000 and image transform applications. It is simple to implement this transform since they can be generated by a single Kronecker product recursion formula. In this paper, a new set of binary code families similar to Walsh codes are obtained based on the concept of code concatenation and permutation. It is shown that these codes can be generated by reconfiguring the Walsh–Hadamard code generator. Hence it can be utilized in reconfigurable radios such as underlay cognitive radio (UCR). Theoretical results showing the BER performance due to MAI between primary users and secondary users in an UCR is also obtained. Simulation results showing the BER performance of these codes in a direct sequence spread spectrum system and UCR system with quadrature multiplexing operating in the individual decoding mode under AWGN plus flat fading Rayleigh channel conditions is also obtained.     

Blind Frequency Ambiguity Resolution in OFDM Systems Using a Linear Precoder

This paper presents a technique of the blind frequency ambiguity resolution for orthogonal frequency division multiplexing systems. The basic idea behind this method is a linear precoding scheme applied to data in predefined subcarriers before the inverse discrete Fourier transform to deploy a correlation structure, thus the integer part of the carrier frequency offset can be estimated after the discrete Fourier transform via cross correlation operations among these subcarriers. Performance analysis is carried out to gain insight into the relationship between the false estimation probability and system parameters. Allocation of these predefined subcarriers is optimized to avoid false estimation. Finally, numerical simulations are conducted to demonstrate the efficiency of the proposed method and the performance comparison with the existing estimators.     

Application of the Joint Fast Walsh Hadamard-Inverse Fast Fourier Transform in a LDPC Coded OFDM Wireless Communication System: Performance and Complexity Analysis

An efficient low complexity T transform which combines the Walsh Hadamard Transform and Discrete Fourier Transform (DFT) into a single fast orthonormal unitary transform is considered for the application in low density parity check coded orthogonal frequency division multiplexing (LDPC-OFDM) across additive white Gaussian noise channel model and multipath fading channel models. The T-transform is developed through the sparse matrices factorization method using Kronecker product scheme. T-transform based COFDM system, which is capable of reducing peak to average power ratio (PAPR) of the transmitted symbols and improving the bit error rate (BER) performance at a reasonable reduced complexity. Several signaling formats such as Quadrature phase shift keying and 16- ary Quadrature amplitude modulation (16-QAM) are considered. A T COFDM system is described which could provide an alternative to DFT-COFDM system, and is therefore a better alternative to balance the transform complexity, PAPR reduction and system performance. Simulation results are used to examine and compare the complexity, PAR and the BER performance of T-OFDM system and DFT-OFDM system. Numerical results show that the T-COFDM system outperforms the DFT-COFDM based in the multipath channel models.     

基于MEMS的新型高场不对称波形离子迁移谱仪

简要回顾了离子迁移谱技术的发展历程,叙述了常规离子迁移谱的局限性。阐述了基于MEMS工艺的新型高场不对称波形离子迁移谱技术,该技术以物质离子的离子迁移率在高场下的非线性变化特性为基础,可实现对物质离子的空间分离。以MEMS技术为主体,自主研发了高场不对称波形离子迁移谱仪,并对挥发性有机物、苯系物、爆炸物和农药等样品进行了检测,结果表明该离子迁移谱仪能够对苯、丙酮、对二甲苯、爆炸物梯恩梯和农药硫丹等物质实现快速、高分辨和高灵敏度检测,检测精度达10-9量级,线性度达0.95。该结果展示了其在物质离子分离检测方面的巨大潜力,以及在环境、食品安全和生物大分子等领域的优越性和前景,其研究成果将推动下一代物质离子分离检测技术的发展。     

Diversity comparison of spreading transforms for multicarrier spread spectrum transmission

Multicarrier spread spectrum transmission methods based on orthogonal frequency division multiplexing employ a linear transform to spread energy of transmitted symbols over statistically independent Rayleigh fading subcarriers, in order to enable a diversity gain at the receiver. We jointly treat the mapping from bits into transmit symbols and the spreading transform as a code in Euclidean space. We describe criteria to identify good and bad spreading transforms, in terms of the asymptotic bit-error probability (BEP) at high signal-to-noise ratio. Upper and lower bounds on the BEP are derived. It is shown that the BEP performance of the commonly used Hadamard transform is asymptotically bad. Alternative orthogonal transforms with better asymptotic performance are proposed. Simulation results are given for the example of 2-phase-shift keying, block length 8.     

一种SAR海洋图像舰船尾迹检测与判别方法

本文针对常规Radon变换域中尾迹峰值检测的不确定性问题,提出了一种基于特征空间决策的尾迹检测算法。该算法首先门限化图像的Radon变换系数,提取出所有可能的峰值点;然后对这些相应的局部峰值的“截面”进行连续小波变换峰值匹配,再根据提取到的参数形成决策矢量在特征空间中进行决策。对仿真和实际数据处理的结果表明,该方法能有效、准确地检测到SAR图像中的舰船尾迹。     

Integer-based constellation-shaping method for PAPR reduction in OFDM systems

In this paper, the problem of reducing the peak-to-average-power ratio (PAPR) in an orthogonal frequency-division multiplexing system is considered. We design a cubic constellation, called the Hadamard constellation, whose boundary is along the bases defined by the Hadamard matrix in the transform domain. Then, we further reduce the PAPR by applying the selective-mapping technique. The encoding method, following the method introduced in the work of Kwok, is derived from a decomposition known as the Smith normal form. This new technique offers a PAPR that is significantly lower than those of the best-known techniques without any loss in terms of energy and/or spectral efficiency, and without any side information being transmitted. Moreover, it has a low computational complexity.