衰减直流分量对傅立叶变换快速算法的影响及其消除办法

针对全周傅立叶变换快速算法在处理含有衰减直流分量的周期信号时会产生误差的问题,分析衰减直流分量在傅立叶快速算法结果的变化规律,对计算结果进行修正,从而得到了各周期分量的精确计算结果。通过计算证实,该方法行之有效。     

同构机群环境下快速傅立叶变换

面向同构机群系统解决了通信和同步、任务调度以及消息在通信链路上的路由等问题。设计和实现了同构机群下计算离散傅立叶变换的快速并行算法。该算法利用对称性进行优化，样本数据长度无任何限制。     

共轭反对称序列的DFT及FFT算法

对共轭反以称复数序列的离散傅立叶变换（DFT）及其快速傅立叶变换（FFT）算法进行了研究,获得了共轭反对称序列的DFT具有实部为0的性质,并开发出适用于共轭反对称序列的FFT算法。该算法与传统的FFT算法相比减少了一半的计算量和存储单元。     

线性调频分数傅立叶变换理论及应用

基于普通傅立叶变换（FT）的特征函数,本文给出了一种连续时间信号的线性调频分数傅立叶变换（CFRFT）的表达方式,在此基础上,分析了CFRFT包括时移特性、展缩特性、反褶特性、时域微分特性、分数域频移特性、时域斜变信号相乘特性和Parseval定理等变换性质,得出一些常用连续时间信号的CFRFT的变换表达式,说明了傅立叶变换可视为分数傅立叶变换（FRFT）的一个特例,对应用分数傅立叶变换分析系统具有启发作用.作为分数傅立叶变换的应用,解决了傅立叶变换不能有效分析时变系统的问题.     

线性调频分数傅立叶变换理论及应用

基于普通傅立叶变换(FT)的特征函数,本文给出了一种连续时间信号的线性调频分数傅立叶变换(CFRFT)的表达方式,在此基础上,分析了CFRFT包括时移特性、展缩特性、反褶特性、时域微分特性、分数域频移特性、时域斜变信号相乘特性和Parseva l定理等变换性质,得出一些常用连续时间信号的CFRFT的变换表达式,说明了傅立叶变换可视为分数傅立叶变换(FRFT)的一个特例,对应用分数傅立叶变换分析系统具有启发作用。作为分数傅立叶变换的应用,解决了傅立叶变换不能有效分析时变系统的问题。     

电器检测的谐波分析算法

低压电器的低频骚扰抗扰度试验中对试验电流进行谐波分析是试验的关键步骤．在分析离散傅立叶变换的谱泄漏和栅栏现象的基础上，通过对时域信号加合适的窗函数，并在频域采用内插算法，有效的减小了测量过程中的频谱泄漏．设计并实现谐波分析软件，在实际应用中取得了良好效果．     

基于小波包变换的电力系统谐波电流检测

针对常规快速傅立叶变换无法检测非整数次谐波,以及改进的加窗插值快速傅立叶变换运用困难,采用小波、小波包变换对电网信号中的谐波进行检测分析。小波包变换建立在二进小波变换基础上,可以实现对信号的均匀划分,能够更好地提取信号的时频特性。仿真结果证明,较之傅立叶变换和小波变换,小波包变换对电网信号中谐波的幅度、频率的估计具有更高的精度。     

基于分裂基快速傅立叶变换的电力系统谐波分析

基于快速傅立叶变换（FFT）的电力系统谐波分析难以实现同步采样和整数周期截断,易造成频谱泄漏,影响谐波分析精度.为提高FFT的精度,比较几个典型的窗函数,提出基于加凯瑟窗的插值分裂基快速傅立叶变换算法.仿真分析结果表明该算法能提高FFT计算精度,满足谐波参数测量的精度要求.     

快速抗混迭傅立叶变换频谱计算法的推证及实用计算公式

对快速抗混迭傅立叶变换（ＦＡＦＴ）算法进行了详细的数学推证,得出了实用的ＦＡＦＴ计算公式,并对其正确性进行了验证。     

基于小波和傅立叶变换组合的数字图像水印算法

数字水印技术是实现版权保护的有效办法之一.为实现水印图像的嵌入,提出了一种基于二维离散小波与傅立叶变换组合的灰度图像数字水印算法.首先对原始图像进行离散小波变换,选择低频子带图像LL作为水印的添加区,再将LL区进行分块,并对每一个小块作离散傅立叶变换;对嵌入的水印图像做相应的分块置乱处理,而后根据人眼视觉系统的特点结合边缘分析将水印信息以不同的强度嵌入载体图像中,最后进行傅立叶和小波逆变换生成密图.实验结果表明,算法具有较好的鲁棒性和视觉效果.     

基于FFT和IFFT实信号处理方法研究

通过研究发现某些复数序列的性质在某种意义上特别有用,这种性质引出的数据处理导致一个序列的产生,该序列在时频两域都具有对称性,能够使用快速傅立叶变换（FFT）算法处理,实现复数计算次数明显的减少,从而提高了信号处理的速度。给出了下标倒置共轭序列和镜象对称复共轭序列的定义。     

基于DFT的雷达回波数据压缩非线性算法

为了更加有效地减少雷达数据的传输带宽和节省数据的存储空间,根据雷达回波信号的特点,研究了基于频域的数据压缩算法．针对雷达回波变换域数据的特点,应用贪婪算法思想,提出了一种新的基于DFT的非线性压缩算法．仿真结果表明,把该方法应用到雷达信号数据压缩中,在保真度方面要优于传统线性的DFT压缩算法．     

海浪能量谱密度函数计算方法

为了充分利用有限观测资料确定海洋结构物设计与营运环境条件,以北海North Alywn平台提供的一次风暴记录为依据,以提高谱峰分辨率和减小谱方差为谱估计目标,在快速傅里叶变换算法(FFT)基础上,引入最大熵算法(MEM)和小波变换算法(WT);为实现对小容量子样有效的谱估计,应用自举理论(BT)在原始子样基础上构建移动...     

介质损耗数字化测量方法综述

介质损耗(简称介损)是一个微小值,外界干扰容易给介损测量造成大的影响,而实时性也是在线监测追求的一个指标,因此高精确度、快速的介损数字化测量方法是介损在线监测系统的关键部分。介绍了目前介损测量时用到的各种数字化测量方法,即对数字化过零比较法、相关函数法、正弦拟合法、傅立叶变换及其改进算法和神经网络法等进行了综合评述,给出了它们的基本原理、分析了它们的性能和优缺点。最后,对介损数字化测量的发展趋势和研究动态提出了看法。     

Adaptive Short-Time Fractional Fourier Transform Based on Minimum Information Entropy

Traditional short-time fractional Fourier transform(STFrFT) has a single and fixed window function, which can not be adjusted adaptively according to the characteristics of frequency and frequency change rate. In order to overcome the shortcomings, the STFrFT method with adaptive window function is proposed. In this method, the window function of STFrFT is adaptively adjusted by establishing a library containing multiple window functions and taking the minimum information entropy as the criterion, so as to obtain a time-frequency distribution that better matches the desired signal. This method takes into account the time-frequency resolution characteristics of STFrFT and the excellent characteristics of adaptive adjustment to window function, improves the time-frequency aggregation on the basis of eliminating cross term interference,and provides a new tool for improving the time-frequency analysis ability of complex modulated signals.     

Research Progress on Discretization of Linear Canonical Transform

Linear canonical transformation(LCT) is a generalization of the Fourier transform and fractional Fourier transform. The recent research has shown that the LCT is widely used in signal processing and applied mathematics, and the discretization of the LCT becomes vital for the applications of LCT. Based on the development of discretization LCT, a review of important research progress and current situation is presented, which can help researchers to further understand the discretization of LCT and can promote its engineering application. Meanwhile, the connection among different discretization algorithms and the future research are given.     

A Time-Frequency Associated MUSIC Algorithm Research on Human Target Detection by Through-Wall Radar

In this paper, a time-frequency associated multiple signal classification (MUSIC) algorithm which is suitable for through-wall detection is proposed. The technology of detecting human targets by through-wall radar can be used to monitor the status and the location information of human targets behind the wall. However, the detection is out of order when classical MUSIC algorithm is applied to estimate the direction of arrival. In order to solve the problem, a time-frequency associated MUSIC algorithm suitable for through-wall detection and based on S-band stepped frequency continuous wave (SFCW) radar is researched. By associating inverse fast Fourier transform (IFFT) algorithm with MUSIC algorithm, the power enhancement of the target signal is completed according to the distance calculation results in the time domain. Then convert the signal to the frequency domain for direction of arrival (DOA) estimation. The simulations of two-dimensional human target detection in free space and the processing of measured data are completed. By comparing the processing results of the two algorithms on the measured data, accuracy of DOA estimation of proposed algorithm is more than 75%, which is 50% higher than classical MUSIC algorithm. It is verified that the distance and angle of human target can be effectively detected via proposed algorithm.     

自傅里叶函数及其应用

列出了一大组基本ＳＦＦ和复合ＳＦＦ，表明由Ｃａｏｌａｌ给出的并不是全部的ＳＦＦ。其次指出了由Ｃａｏｌａ以及Ｌｏｈｍａｎｎ等先后提出的由任意函数构造一个ＳＦＦ的定义式的局限性，进一步提出了由奇函数构造一个ＳＦＦ的定义式以及反相ＳＦＦ的概念。最后讨论了ＳＦＦ的一些重要性质及应用。     

一类素因子分解FFT算法

提出了一类新的素因子分解ＦＦＴＸ法（ＰＦＡ）．该算法可以用非同址的方式实现，也可以用同址的方式实现；既可以输入输出皆为同一顺序而不需要混序，也可以输入输出不为同一顺序而需要混序．同时，还具有新的算法结构，在计算每一维的小数ＤＦＴ时，需要变换数据模块的地址．理论分析与计算机仿真实验证明，与传统ＰＦＡ相比，本文算法可无需混序操作，易于扩展，可同址运算和顺序输入输出，能节省存贮量，提高运算速度。     

Novel LFM Jammer Suppression Algorithm for DSSS in FRFT Domain

A novel algorithm is proposed to resolve the defects in the traditional linear frequency modulation (LFM) jamming suppression algorithm in the fractional Fourier transform (FRFT) domain. The traditional LFM jamming suppression algorithm in the FRFT domain has some defects. For example, the exact threshold is difficult to set and both the signal-to-noise ratio (SNR) loss and spectrum leakage are serious in strong jamming-to-signal ratio (JSR) situations. Windowing, overlapping and inverse windowing techniques are used in the FRFT domain to reduce the spectrum leakage and the SNR loss. Under the condition that only the direct sequence spread spectrum (DSSS) signal and white Gaussian noise are present, the amplitude of the received signal after FRFT is assumed to be Rayleigh distributed. Based on the distribution characteristic, hypothesis testing is used to suppress the jamming spectrum using the algorithm. Simulation results show that the performance of proposed algorithm is better than that of the conventional algorithms, especially in a strong jamming and multi component LFM jamming environment.