用DFT研究DPCM系统

本文用离散Ｆｏｕｒｉｅｒ变换（ＤＦＴ）研究ＤＰＣＭ系统。预测误差是原信号和预测系数的循环卷积，耐解调由Ｆｏｕｒｉｅｒ变换实现。在这种ＤＰＣＭ中，预测前还可以对图像作平滑等处理以减小预测误差。     

语音信号的频域非线性波形编码

本文主要研究语音信号的分段离散Ｆｏｕｒｉｅｒ变换（ＤＦＴ）波形编码。提出新的信号分析工具——非线性ＤＦＴ，它不仅表征了时间序列的局部线性信息，而且也包含有时间序列的全局大范围的二阶（平方）非线性特征，因此它具有比线性ＤＦＴ更强的信号分析能力。利用该ＤＦＴ对一长分段（如，５１２或者１０２４个样点）语音信号进行波形编码，在获得较高的压缩比（压缩比为８或１６）的情况下，能很好地保持原语音信号波形的细节特征。     

子波变换及其在光信息处理中的应用

子波变换及其在光信息处理中的应用杨罕，李爱民，聂守平，卞松龄（南京理工大学４３２教研室南京２１００９４）子波变换是光信息处理中的一个重要工具，与常用的Ｆｏｕｒｉｅｒ变换、Ｇａｂｏｒ变换相比在分析瞬态信号方面有很多优点。本文详细介绍了子波变换的基本原理...     

采用小波变换对短数据信号的谱估计方法

本文提出一种新的信号估计方法－－小波变换，理论与仿真结果证明，在短数据信号情况下，基于小波变换的谱估计方法其分辨率要高于ＦＦＴ方法，文中详细讨论了小波的谱估计算法，并给出了双正弦信号的仿真结果。     

采用离散傅立叶变换对CATV系统中DFB激光器非线性特性的分析

本文首次提出了一种新的分析ＣＡＴＶ系统中的ＤＦＢ发射光源的非线性失真的方法，该方法基于ＤＦＢ激光器的输入－输出信号的映射函烽，从信号分析的观点出发，采用离散傅立叶变换，直接得出ＣＡＴＶ系统衡量非线性失真的测试参量。     

用Chirp—z变换获得雷达目标回波波形特征

探讨了高分辨率雷达视频回波波形特征．提出对回波信号作Ｃｈｉｒｐ－ｚ变换，以提高频谱的分辨率．还对两类实测毫米波高分辨率雷达目标回波波形进行了Ｃｈｉｒｐ－ｚ变换及Ｆｏｕｒｉｅｒ变换，并对两类结果进行了比较，结果证明对雷达回波波形作Ｃｈｉｒｐ－ｚ变换获得的视频波形特征既满足同一目标特征稳定性，又容易区分两类不同目标．     

用MoM－CGM－FFT分析二维电磁散射问题

本文提出一种ＭｏＭ－ＣＧＭ－ＦＦＴ（矩量法－共轭梯度法－快速富立叶变换）的混合技术来分析任意截面和非均匀介质柱的做射问题。该方法是以等效电流作为未知函数进行求解。该方法适应世广，是一种求解电磁散射问题的简单途径。由于应用了ＣＧＭ－ＦＦＴ技术，降低了所需计算机内存和ＣＰＵ时间，可以有效地处理电子尺寸的柱体散射和非均匀介质柱的散射，本文给出的数据和准确结果相比较，吻合好。     

用MoM—CGM—FFT分析二维电磁散射问题

本文提出一种ＭｏＭ－ＣＧＭ－ＦＦＴ（矩量法－共轭梯度法－快速富立叶变换）的混合技术来分析任意截面各非均匀介质柱的散射问题，该方法是以等效电流作为未知函数进行求解，该方法适应性广，是一种求解电磁散射问题的简单途径，由于应用了ＣＧＭ－ＦＦＴ技术，降低了所需计算机内存和ＣＰＵ时间，可以有效地处理电子尺寸的柱体散射和非均匀介质柱的散射，本文给出的数据和准确结果相比比较，吻合好。     

高压RESURF LDMOSFET的实现

利用ＲＥＳＵＲＦ技术，使用常规低压集成电路工艺，实现了适用于ＨＶＩＣ、耐压达１０００Ｖ的ＬＤＭＯＳＦＥＴ。本文介绍了该高压ＬＥＭＯＳＦＥＴ的设计方法、器件结构、制造工艺测试结果，此外，本文还从实验和分析的角度探讨了覆盖在漂移区上面的金属栅－金属栅场板长度ＬＦ对ＲＥＳＵＲＦ器件耐压的影响。     

光接收模块HFBR—2115T的特点及其在光纤接入网中的应用（刊中刊）

介绍了惠普公司生产的光接收模块ＨＦＢＲ－２１１５Ｔ的特点，给出了ＨＦＢＲ－２１１５Ｔ在光纤接入网中的应用方法。     

The fractional Fourier transform and time-frequency representations

The functional Fourier transform (FRFT), which is a generalization of the classical Fourier transform, was introduced a number of years ago in the mathematics literature but appears to have remained largely unknown to the signal processing community, to which it may, however, be potentially useful. The FRFT depends on a parameter α and can be interpreted as a rotation by an angle α in the time-frequency plane. An FRFT with α=π/2 corresponds to the classical Fourier transform, and an FRFT with α=0 corresponds to the identity operator. On the other hand, the angles of successively performed FRFTs simply add up, as do the angles of successive rotations. The FRFT of a signal can also be interpreted as a decomposition of the signal in terms of chirps. The authors briefly introduce the FRFT and a number of its properties and then present some new results: the interpretation as a rotation in the time-frequency plane, and the FRFT's relationships with time-frequency representations such as the Wigner distribution, the ambiguity function, the short-time Fourier transform and the spectrogram. These relationships have a very simple and natural form and support the FRFT's interpretation as a rotation operator. Examples of FRFTs of some simple signals are given. An example of the application of the FRFT is also given     

分数Fourier变换、矩阵群和时-频分析

本文从矩阵群的观点出发讨论了分数Fourier变换的数学描述并通过数字仿真直观地说明了它进行信号时-频分析的两个特点.结果表明,在矩阵描述下,经典的Fourier变换相当于一个置换矩阵;一般的分数Fourier变换相当于一个广义置换矩阵;分数Fourier变换全体构成的变换族可以用一个矩阵群来描述,多次变换运算完全转化为相应的矩阵乘法运算.最后,数字信号分数Fourier变换的仿真计算表明,分数Fourier变换具有独特的时-频分析性质.     

Discrete fractional Fourier transform based on orthogonalprojections

The continuous fractional Fourier transform (FRFT) performs a spectrum rotation of signal in the time-frequency plane, and it becomes an important tool for time-varying signal analysis. A discrete fractional Fourier transform has been developed by Santhanam and McClellan (see ibid., vol.42, p.994-98, 1996) but its results do not match those of the corresponding continuous fractional Fourier transforms. We propose a new discrete fractional Fourier transform (DFRFT). The new DFRFT has DFT Hermite eigenvectors and retains the eigenvalue-eigenfunction relation as a continous FRFT. To obtain DFT Hermite eigenvectors, two orthogonal projection methods are introduced. Thus, the new DFRFT will provide similar transform and rotational properties as those of continuous fractional Fourier transforms. Moreover, the relationship between FRFT and the proposed DFRFT has been established in the same way as the conventional DFT-to-continuous-Fourier transform     

Tomography time-frequency transform

The paper shows that the fractional Fourier transform (FRFT) of a signal is the Radon transform of the time-frequency distribution of the same signal. Therefore, a time-frequency distribution known as the tomography time-frequency transform (TTFT) is defined as the inverse Radon transform of the FRFT of the signal. Because the computation of the TTFT does not explicitly require any window or kernel function, high resolutions in both the frequency and time domains can be achieved. When the signal contains multiple components, the cross terms can be effectively removed by an adaptive filtering process that is applied on the FRFT rather than the final result. Therefore, distortions made by the filtering process on the desired signal components can be minimized     

基于一种新的交换矩阵的离散分数阶傅立叶变换实现

分数阶傅立叶变换比傅立叶变换更具有一般性,多年来引起人们深入研究.由于连续的分数阶傅立叶变换在工程实现时都要抽样离散化,直接对连续分数阶傅立叶变换的核离散化会失去很多重要的性质,因此人们研究它的离散实现并保持它具有与连续分数阶变换同样的性质.本文提出了一种新的交换矩阵实现离散分数阶傅立叶变换,其变换的离散核矩阵与连续变换的分数阶傅立叶变换核有相似性,诸如酉特性、可加性、正交性和可逆性.仿真结果证实了所提出的分数阶傅立叶变换核与连续分数阶傅立叶变换核的相似性以及两种变换对矩形信号这种典型信号的分数阶傅立叶变换的相似性.     

Generalized convolution theorem associated with fractional Fourier transform

The fractional Fourier transform (FRFT)—a generalization of the well‐known Fourier transform (FT)—is a comparatively new and powerful mathematical tool for signal processing. Many results in Fourier analysis have currently been extended to the FRFT, including the ordinary convolution theorem. However, the extension of the ordinary convolution theorem associated with the FRFT has been developed differently and is still not having a widely accepted closed‐form expression. In this paper, a generalized convolution theorem for the FRFT is proposed, and the dual of it is also presented. The ordinary convolution theorem and some of its existing extensions related to the FRFT are shown to be special cases of the derived results. Moreover, some applications of the derived results are presented. Copyright © 2012 John Wiley & Sons, Ltd.     

基于FRFT的复合chirp信号分析

作为Fourier变换的一种广义形式,分数阶傅里叶变换（FR订）同时融合了信号在时域和频域的信息,是一种新的时频分析方法。而复合线性调频（chirp）信号相对单斜率线性调频信号具有更好的速度分辨力和距离速度联合分辨力。为了分析该信号的特征,提出了一种基于分数阶Fourier变换的分析方法。由于复合chirp信号在FR丌域呈现的冲激特性,以此实现复合chirp信号的检测。实验结果表明．该方法对复合chim信号的检测是有效的。     

一种基于分数阶Fourier变换的雷达运动目标检测算法

针对雷达回波为多分量LFM信号时,时频分析存在的交叉项干扰问题,提出了一种基于分数阶Fourier变换(Fractional Fourier Transform,FRFT)的伪Wigner分布(PWD).该方法通过在参数平面按阈值进行峰值搜索确定变换域阶次,再在相应的分数阶Fourier域计算PWD,有效地抑制了交叉项的干扰,有利于更好地提取信号的时频信息.仿真实验证明了在强背景噪声下该算法的有效性.     

一种新的变换域自适应LMS滤波算法

为了改善时变系统中的LMS算法收敛速度,一般可以在变换域进行自适应处理。通过研究和分析分数阶傅里叶变换与时-频平面的关系,提出在分数阶傅里叶变换域进行自适应时-频滤波。所提出的方法首先搜索最佳变换域,然后在分数阶傅里叶变换域进行LMS自适应滤波。仿真结果表明,与目前一些基于变换域的方法对比,新方法通过对时-频平面的旋转,可以显著加速算法收敛性。