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Discrete Gabor transform 总被引:10,自引:0,他引:10
A feasible algorithm for implementing the Gabor expansion, the coefficients of which are computed by the discrete Gabor transform (DGT), is presented. For a given synthesis window and sampling pattern, computing the auxiliary biorthogonal function of the DGT is nothing more than solving a linear system. The DGT presented applies for both finite as well as infinite sequences. By exploiting the nonuniqueness of the auxiliary biorthogonal function at oversampling an orthogonal like DGT is obtained. As the discrete Fourier transform (DFT) is a discrete realization of the continuous-time Fourier transform, similarly, the DGT introduced provides a feasible vehicle to implement the useful Gabor expansion 相似文献
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基于尺度可变的傅氏变换实现比例不变的相关识别 总被引:2,自引:2,他引:0
在透镜的傅氏变换中 ,改变物与后焦面的距离可灵活调整物的频谱的空间尺寸 ,结合匹配滤波实现比例不变的相关识别 ;采用数字全息记录物波 ,免去干版的化学处理 ,可实现自动化相关识别 ,并使相关峰更尖锐 相似文献
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An improved pulsed microwave spectrometer for the detection of rotational transitions in gaseous molecules in the frequency range of 130–150 GHz is described. It incorporates a tunable Fabry-Perot cavity and a low noise superneterodyne receiver for the detection of the molecular emission signals. The molecules are excited by π/2 pulses provided by a high efficiency frequency doubler which is pulse modulated at an IF frequency of 1.4 GHz. 相似文献
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Soo-Chang Pei Min-Hung Yeh Chien-Cheng Tseng 《Signal Processing, IEEE Transactions on》1999,47(5):1335-1348
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 相似文献
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A filterbank in which cyclic convolutions are used in place of linear convolutions will be referred to as a cyclic convolution filterbank (CCFB). A dyadic tree-structured CCFB can be used to perform a discrete wavelet transform suitable for coding based on symmetric extension methods. This paper derives two types of efficient implementation techniques for the tree-structured CCFB: one using complex arithmetic and one using only real arithmetic. In addition, the present paper analyzes in detail the perfect reconstruction (PR) condition for the two-channel CCFB and shows that this condition is much less restrictive than that of usual two-channel filterbanks. When each of the two-channel CCFBs constituting a tree-structured CCFB is designed to be PR, the whole system is PR. A quadrature mirror filter (QMF) CCFB having the PR property is demonstrated to be easily designed using a standard filter design subroutine. In contrast, designing a linear-phase PR FIR QMF bank that has good frequency response is not possible when filters are realized by linear convolutions. 相似文献
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基于log-Gabor与FT数据融合的掌纹识别算法 总被引:1,自引:0,他引:1
本文提出一种基于数据融合的掌纹识别算法。该算法首先利用log-Gabor小波提取掌纹纹理特征,同时用傅立叶变换(Fourier Transform,FT)提取掌纹频域统计特征,然后分别与库中模板进行匹配,最后对两种匹配结果进行数据融合,得到最终识别结果。该算法中的基于手掌中基准点的手掌定位方法,使得定位中的方向校正更为准确。实验结果达到较高的识别率,验证了该算法的有效性。 相似文献
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A method of computing the discrete cosine transform using the iterative arithmetic Fourier transform is presented. It overcomes the difficulty of dense, Farey-fraction sampling in the time domain or space domain when using the original arithmetic Fourier transform (AFT) algorithm. Also, dense transform-domain samples are obtained without any interpolation or zero-padding. These dense samples can be advantageously used for accurate parameter estimation or determination of a few principal components. The inverse discrete cosine transform can be efficiently computed from these dense, Farey-fraction transform-domain samples using the original AFT. The resulting structure is suitable for VLSI implementation. 相似文献
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Ding Hanyi Li Hong Zhang Guangzhao 《Journal of Infrared, Millimeter and Terahertz Waves》1992,13(4):425-432
The principle and fundamental structure of a millimeterwave electric-field cross-correlation Fourier transform spectrometer are presented. In the spctrometer, two pseudorandom binary sequences (PRBS) with controllable phase variation are used to modulate individually two wide bandwidth microwave signals with variable phase delay are obtained. And the Fourier transform of the crosscorrelation function of these microwave signals is the cross-power spectrum. Some experimental results about the spectrometer are given in 8mm-wave range. 相似文献
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YueBing ZhaoYuexia XuZhoujun FuHongjuan MaFengning 《电子科学学刊(英文版)》2004,21(2):135-139
A set of discrete points obtained from audit records on a behavior session is processed with Fourier transform. The criterion of selecting Fourier transform coefficients is introduced, and is used to find a unified value from the set of coefficients. This unified value is compared with a threshold to determine whether the session is abnormal. Finally simple test results are reported. 相似文献
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通过傅里叶变换在频域中对光纤F-P传感器的透射光谱进行研究,简化了腔长解调的过程,使得腔长解调变得简单且易于控制。主要从理论上分析了光纤F-P传感器透射光谱的特性和影响因素,对光纤F-P传感器的并联复用和串联复用的傅里叶变换解调方法进行了研究和讨论,同时利用数值模拟仿真研究了光纤F-P传感阵列应变传感的规律。 相似文献
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WANG Dong-sheng WANG Gui-mei PAN Wei-wei WANG Yu-tian 《光电子快报》2008,4(2):147-149
A sapphire fiber thermal probe with Cr^3+ ion-doped end was grown using the laser heated pedestal method. The fluorescence thermal probe offers advantages of compact structure, high performance and the ability to sustain high temperature from the room temperature to 450℃. Based on the fast fourier transform (FFT), the fluorescence lifetime is obtained from the tangent function of the phase angle of the first non-zeroth item of FFT result. Compared with other traditional fitting methods, our method has advantages such as fast speed, high accuracy and being free from the influence of the base signal. The standard deviation of FFT method is about half of that method. In addition, since the FFT method is immunity to analysis can be skipped. of the Prony method and close to the one of the Marquardt the background noise of the signal, the background noise 相似文献
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Design of time-frequency distributions (Tfds) that are robust to the impulse noise influence is considered. The robustTfds based on the robust short-time Fourier transform (Stft) are proposed. An efficient procedure to evaluate the robustStft is given. RobustTfds based on the robustStft have better energy concentration around the signal instantaneous frequency (If) than the robustStft itself. Also, theseTfds are more resistant to higher impulse noise than the robustTfds obtained using the local autocorrelation function (Laf) based minimization problem. 相似文献
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A two-grid polarization rapid scan interferometer for the measurement of Electron Cyclotron Emission from the LT-4 Tokamak is described. The instrument incorporates two scanning mirrors, and a back e.m.f. derived mirror position monitor 相似文献
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Typographical errors were printed in the print and online versions of the original article. The correct versions of Equation
25 (page 168), Figure 6(c) (page 169), and Table 2 (page 170) are printed below, respectively.
The online version of the original article can be found at 相似文献
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The Van Vleck equation relating the polarity correlation function to the direct correlation function is used to derive a new algorithm for the evaluation of the discrete Fourier transform of the direct correlation function. Application of an implementation of the algorithm to correlation-based measurement is discussed. 相似文献
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