星载海洋雷达高度计中基于FPGA的FFT运算模块的实现及性能分析

FFT运算是星载海洋雷达高度计实时跟踪处理的重要步骤，现代高分辨率雷达高度计要求处理速度更高，这时如果采用软件来进行FFT运算会导致处理时间过长。考虑到上星的需要，提出了一种采用FPGA技术来硬件实现高度计的FFT运算方法，理论和实验结果证明，采用此技术完全能满足高度计有关精度和处理速度的要求，解决了高分辨率星载雷达高度计控制中的一项关键的技术问题。     

A fast integral approach for drag force calculation due to oscillatory slip stokes flows

In this paper, we describe an efficient numerical method for modelling oscillatory incompressible slip Stokes flows in three dimensions. The efficiency is achieved by employing an integral approach combined with an accelerated boundary‐element‐method (BEM) solver. First the integral representations for slip flows with two different slip models are formulated. The resulting integral equations are then solved using the BEM combined with the precorrected‐FFT accelerated technique. 3D numerical codes have been developed based on the method described above. These codes are then used to calculate the drag forces on oscillating objects immersed in an unbounded slip flow. Three objects are considered, namely a sphere, a pair of plates and a comb structure. The simulated drag forces on these objects obtained from the two slip models are compared. In the sphere case, the simulated results are also compared with the analytical solutions for both the steady‐state case and the no‐slip oscillatory case and are found to be in good agreement. In addition, qualitative comparison of the simulation results with the experimental results in the plate problem is also presented in this paper. Copyright © 2004 John Wiley & Sons, Ltd.     

快速傅立叶变换（FFT）在TMS320F206上的实现

对快速傅立叶变换(FFT)在数字信号处理器(DSPs)F206上实现中出现的计算溢出、倒序排列等问题进行了分析并提出了解决方法，同时对快速傅立叶变换(FFT)的特点进行了研究和总结；据此编写出FFT在F206上实现的流程图；根据实验结果，给出了不同长度的FFT运算在F206上实现的运算时间和精度。该结果表明此方法用于一般的信号处理和工业控制中都能达到精度和实时性的要求。     

一种抗几何变换的图像盲水印算法

为解决在几何变换时水印无法检测的问题,提出了一种抗几何变换的图像盲水印算法.该算法基于傅立叶变换和对数极坐标变换,实现了可以提取有意义字符的抗几何变换的盲水印算法.在嵌入水印过程中,通过对原始图像进行傅立叶变换,并选择中频部分进行对数极坐标转换变换,然后进行傅立叶变换,将水印嵌入幅度谱矩阵中.在提取水印过程中,结合模板矫正来降低各种积累误差,进行相应的反变换,并用局部最大检测法来提取水印.实验表明,该算法具有较强的鲁棒性,对几何变换、裁剪、压缩、锐化和涂改等抵抗性较强.     

基于DSPs的同步采样系统及其在电力监控中的应用

设计了一种基于MAX125A／D转换芯片和TMS320F206数字信号处理器的采样系统，可以实现对三相电压和电流的同时采样，不但提高了采样速度，而且消除了电压和电流相位差的测量误差；提出了一种利用硬件测频电路计算频率偏差的方法，此方法使得在谐波分析时简化了各次谐波幅值和相角的修正计算。本采样电路已经应用于电力系统的FTU(馈线自动化终端单元)中。     

液晶材料特性动态DSP测试系统

为得到液晶材料的连续响应特性及研究其损坏机理,本文的测试系统采用TI公司的DSP芯片,配合幅度频率连续可控的高压交流信号源,用FFT抽取基波参数得到动态响应,通过电压捕获实现整周期采样,通过曲面插值校正动态测量误差,保证了数字信号处理的精度.     

Simulation of non-Gaussian surfaces with FFT

A numerical procedure for the simulation of non-Gaussian surfaces has been developed. Fast Fourier Transform is used to generate the surfaces. The amplitude part is constructed from given spectral density or auto-correlation function. The phase part is obtained by using Johnson translator system. By iteration, this method can simulate surfaces with given skewness and kurtosis and with spectral density or auto-correlation function.     

FFT算法在微控制器上的设计与实现

文中描述了一种针对快速傅里叶变换(FFT)嵌入式运算系统的设计,基于ST公司ARM架构的微控制器STM32F4,该控制器拥有强大的数据运算处理能力,在硬件架构以及数据、信号处理上做出了独特的设计。着重介绍了基于Cortex-M4的FFT软件实现,应用,以及数据采样,运算等一系列问题,最后明确了下一步的研究方向。     

基于PMF-FFT的伪码捕获算法分析

建立了PMF-FFT算法的数学模型,分析了相关器个数、相关积累长度和FFT点数对积累损失、扇贝损失和频率分辨率的影响。在此基础上,结合算法的效率和运算量,给出了PMF-FFT算法参数选择的原则和依据。     

A generation method of artificial fluctuation data of wind power output considering smoothing effect

To use realistic wind power fluctuation data is important in simulating frequency change of power systems. It is well known that the smoothing effect must be taken into account when generating the artificial wind power output. Therefore, this paper proposed a new method to generate fluctuation waveform considering smoothing effect based on random number to fulfill the correlation among multiple sites and autoregression model. The effectiveness of the proposed method was tested by using practical wind speed data measured in Tohoku district.