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The effects that anesthesia has on the surgical patient can be characterized with the electroencephalogram (EEG). These effects are typically quantified through frequency analysis of the EEG signal. The fast Fourier transform (FFT) is usually employed for this purpose. In recent years, the fast Walsh transform (FWT) has been proposed as an alternative to the FFT for signal analysis because it is computationally more efficient, requiring less time to complete on a digital computer. This paper statistically evaluates the quantitative and dynamic differences between the results of Walsh and Fourier analysis of the EEG done for the purpose of characterizing the effects of anesthesia. This paper shows that there are quantitative differences between the results of the two frequency analysis techniques but they are dynamically equivalent, both showing essentially the same changes due to the effects of anesthesia. The efficiency of the FWT has been reconfirmed. These results support the use of the FWT in place of the FFT for tracking the effects of anesthesia on surgical patients with the EEG. 相似文献
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Madkour M.F. Gupta S.C. Wang Y.-P.E. 《Wireless Communications, IEEE Transactions on》2002,1(1):169-177
In this paper, successive intracell interference cancellation (IIC) of the wideband-code division multiple access (W-CDMA) signal at the mobile unit is considered. Three new interference cancellation techniques suitable for the downlink of any CDMA system with orthogonal spreading are proposed. No prior knowledge of users' spreading codes or even their spreading factors are required for interference cancellation. A new term, effective spreading code, has been introduced, which is defined as the interfering user physical code as seen by the desired user within the desired user symbol duration. The mobile receiver estimates the effective spreading codes of the interfering users regardless of their spreading factors using fast Walsh transform (FWT) correlators (instead of the regular correlators) and uses this information to suppress the intracell multiuser interference. Three different interference-suppressing techniques are studied: subtraction; combined interfering signal projection; and separate interfering signal subspace projection. The complexity of the proposed techniques is low compared to conventional interference cancellation techniques. For a W-CDMA system and the IMT-2000 vehicular channel model, a capacity increase of up to 150% of the original (without IIC) system capacity is shown 相似文献
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一种基于FPGA的数字下变频算法研究 总被引:2,自引:0,他引:2
在宽带中频软件无线电系统中,数字下变频(DDC)是其核心技术之一。介绍了数字下变频的原理,给出了一种基于FPGA的数字下变频算法,讨论了DDC算法中的关键部分数字锁相环(DPLL)、数字滤波器(DF)和数控振荡器(NCO)的实现,并且比较了这种算法与其他实现方法的优缺点。最后对该算法进行了仿真验证。 相似文献
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数字下变频技术是软件无线电的关键技术之一.本文介绍了AD公司新近推出的高性能数字下变频(DDC)器件AD6636的主要特性和工作原理,通过对宽带和窄带信号滤波器的仿真结果,提出了在数字中频接收机(DIFR)的设计中,能够利用AD6636片内高精度的数字正交下变频器和抽取滤波器,同时利用FPGA实现宽带滤波,可以弥补AD6636的宽带滤波性能较差的缺陷,从而实现宽带数字滤波. 相似文献
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Walsh-like functions and their relations 总被引:2,自引:0,他引:2
Falkowski B.J. Rahardja S. 《Vision, Image and Signal Processing, IEE Proceedings -》1996,143(5):279-284
A new discrete transform, the `Haar-Walsh transform', has been introduced. Similar to well known Walsh and non-normalised Haar transforms, the new transform assumes only +1 and -1 values, hence it is a Walsh-like function and can be used in different applications of digital signal and image processing. In particular, it is extremely well suited to the processing of two-valued binary logic signals. Besides being a discrete transform on its own, the proposed transform can also convert Haar and Walsh spectra uniquely between themselves. Besides the fast algorithm that can be implemented in the form of in-place flexible architecture, the new transform may be conveniently calculated using recursive definitions of a new type of matrix, a `generator matrix'. The latter matrix can also be used to calculate some chosen Haar-Walsh spectral coefficients which is a useful feature in applications of the new transform in logic synthesis 相似文献
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Gray code is a natural way of ordering binary vectors in dyadic space, hence it appears frequently in connetion with Walsh functions. In Paley's definition of Walsh functions their sequencies are arranged in Gray code. Gray code also appears in a new Walsh function generation algorithm which obtains a function by locating all its sign changes. There are certain computational advantages in using Gray code rather than sequency ordering. Examples in fast Walsh transform, dyadic convolution and digital filtering are given. Methods of Gray code to binary conversion are discussed. 相似文献
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基于多相滤波的宽带数字接收机二次变频设计 总被引:1,自引:0,他引:1
分析了基于多相滤波结构的宽带侦察接收机中频数字信号下变频处理方法。在简要说明多相滤波结构的基础上,介绍了基于多相滤波结构的数字下变频实现方法,重点分析了一种二次变频结构,该结构可以极大简化接收机设计,且具有很大的灵活性。最后通过Simulink仿真验证了该结构的合理性和正确性。 相似文献
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This paper first presents a fastW-transform (FWT) algorithm for computing one-dimensional cyclic and skew-cyclic convolutions. By using this FWT in conjunction with the fast polynomial transform (FPT), an efficient algorithm is then proposed for calculating the two-dimensional cyclic convolution (2D CC). Compared to the conventional row-column 2D discrete Fourier transform algorithm or the FPT Fast Fourier transform algorithm for 2D CC, the proposed algorithm achieves 65% or 40% savings in the number of multiplications, respectively. The number of additions required is also reduced considerably. 相似文献
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数字下变频(DDC)是中频数字接收机的关键技术,通过将宽带大数据流变成窄带低数据流,以便DSP实时处理。本文提出一种基于多相滤波结构的正交数字下变频方案,通过计算机和DSP仿真,证明了它的可行性。 相似文献
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Data shuffling in a particular order is frequently required in signal processing applications. The authors present fast recursive algorithms, of order O (N ), for shuffling a data sequence in various orders, e.g. bit reversed, Gray code, and other related orders, under a unified framework. These algorithms are computationally efficient in that every permutation index is essentially computed by a single logical or arithmetic operation between a previous index and a proper offset. The proposed algorithms can be used for the fast Fourier transform, fast Hartley transform, and mutual conversion among three typical forms of the Walsh transform 相似文献
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基于ISL 5416的数字下变频原理及实现 总被引:2,自引:0,他引:2
介绍了软件无线电中数字下变频的原理和实现过程,以及Intersil公司生产的DDC芯片ISL 5416可编程数字下变频器的结构和工作过程,在此基础上,以多通道相关干涉仪系统作为应用背景,对其中数字下变频器件在不同工作带宽下的输出数据进行了分析,说明了ISL 5416能灵活地实现多种带宽下的信号下变频,为解决软件无线电中的可变带宽数字下变频提供了解决方案。 相似文献
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《IEEE transactions on information theory / Professional Technical Group on Information Theory》1977,23(1):144-146
Walsh-type signals exciting memoryless power-law systems are considered. The input is assumed to consist of a sum of weighted Walsh functions. A method is given for finding the weights of the Walsh functions in the output when the input is a finite Walsh series. It is shown that the fast Walsh transform can be used to facilitate the necessary computation. 相似文献
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对软件无线电接收机中数字下变频理论进行深入分析,提出了一种基于多类滤波器级联技术的DDC实现方案。采用疏状滤波器、半带滤波器和整形FIR滤波器级联实现数字下变频的抽取滤波,有效减少了乘法器和加法器需求及滤波器阶数,高效实现了数字下变频,达到了系统的设计要求。最后将该技术与传统的FIR滤波方法进行对比,进一步说明其可行性和优越性。 相似文献
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《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1967,55(10):1664-1674
The fast Fourier transform is a computational tool which facilitates signal analysis such as power spectrum analysis and filter simulation by means of digital computers. It is a method for efficiently computing the discrete Fourier transform of a series of data samples (referred to as a time series). In this paper, the discrete Fourier transform of a time series is defined, some of its properties are discussed, the associated fast method (fast Fourier transform) for computing this transform is derived, and some of the computational aspects of the method are presented. Examples are included to demonstrate the concepts involved. 相似文献
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m序列复合码的一种快速相关算法 总被引:3,自引:0,他引:3
在直扩系统中,PN码的快速捕获十分重要。由于m序列的优选对有限,故在实际应用中采用复合码作为PN 码。常用的复合码主要有Gold序列和Kasami小集合序列。本文提出了一种利用快速沃尔什变换(FWT)实现对复合码进行快速相关的算法。这种算法适用于由两个m序列模2加形成的复合码,并原则上可以推广到Kasami大集合序列的捕获上。分析表明,我们提出的算法与传统相关算法相比,降低了算法的时间复杂度。 相似文献