共查询到20条相似文献,搜索用时 62 毫秒
1.
本文首先简单回顾了作者曾提出的二维实值离散Gabor变换及其与复值离散Gabor变换的简单关系,然后着重探讨了二维实值离散Gabor变换快速计算问题,提出了二维实值离散Gabor变换系数求解的时间递归算法以及由变换系数重构原图像的块时间递归算法,研究了双层并行格型结构实现算法的方法,计算复杂性分析及与其它算法的比较证明了双层并行格型结构实现方法在实时处理方面的优越性。 相似文献
2.
Rahman A. Das S. Chandrakasan A.P. Reif R. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2003,11(1):44-54
In this paper, analytical models for predicting interconnect requirements in field-programmable gate arrays (FPGAs) are presented, and opportunities for three-dimensional (3-D) implementation of FPGAs are examined. The analytical models for two-dimensional FPGAs are calibrated by routing and placement experiments with benchmark circuits and extended to 3-D FPGAs. Based on system-level modeling, we find that in FPGAs with more than 20 K four-input look-up tables, the reduction in channel width, interconnect delay and power dissipation can be over 50% by 3-D implementation. 相似文献
3.
Neacsu D.O. Wagner E. Borowy B.S. 《Industrial Electronics, IEEE Transactions on》2008,55(4):1628-1636
A solution for high current applications consists of paralleling power stages of lower power. Given the complexity of these systems, a comprehensive computer-based analysis is required before physical implementation. This paper presents a simulation benchmark for selection of the pulsewidth modulation (PWM) algorithms used to control interleaved three-and four-wire three-phase power inverters. The analysis considers the resulting phase current harmonics, dc link current harmonics, neutral point voltage, and inter converter circulation currents. Analytical aspects of different current control structures used within interleaved power electronics systems and effects of selecting various PWM algorithms are revealed for both the three-wire and the four-wire structure. Finally, analysis of the DSP implementation for different practical solutions is shown. 相似文献
4.
In the tensor representation, a two-dimensional (2-D) image is represented uniquely by a set of one-dimensional (1-D) signals, so-called splitting-signals, that carry the spectral information of the image at frequency-points of specific sets that cover the whole domain of frequencies. The image enhancement is thus reduced to processing splitting-signals and such process requires a modification of only a few spectral components of the image, for each signal. For instance, the alpha-rooting method of image enhancement can be fulfilled through processing separately a maximum of 3N/2 splitting-signals of an image (N x N), where N is a power of two. In this paper, we propose a fast implementation of the a-rooting method by using one splitting-signal of the tensor representation with respect to the discrete Fourier transform (DFT). The implementation is described in the frequency and spatial domains. As a result, the proposed algorithms for image enhancement use two 1-D N-point DFTs instead of two 2-D N x N-point DFTs in the traditional method of alpha-rooting. 相似文献
5.
Szn-Lin Su Jau-Ming Wu 《Communications, IEEE Transactions on》1997,45(7):800-808
Two systematic schemes to combine block-coded modulation (BCM) and trellis-coded modulation (TCM) are proposed. In the first scheme, the signal points which are used in TCM should be partitioned by the proper BCM systems constructed by a multilevel construction method. The asymptotic coding gain will be 6.02-3.01/n dB, where n is the length of the BCM systems. Since the average transmission power can be reduced by using a denser signal lattice, the main idea of the second scheme is to construct the TCM system based on the signal points of a denser lattice formed by a proper BCM system. Hence, we can get a higher coding gain which is a combination of both the distance gain of TCM and the density gain of BCM. Theoretically, the net coding gain of this proposed scheme can reach 5.27 dB in the case of an 8-D constellation and 7.15 dB in the case of a 16-D constellation. For practical implementation, the phase ambiguity problems for both schemes are considered and solved by a differential encoder/decoder 相似文献
6.
Prats M.M. Franquelo L.G. Portillo R. Leon J.I. Galvan E. Carrasco J.M. 《Power Electronics Letters, IEEE》2003,1(4):110-114
A three-dimensional (3-D) space vector algorithm of multilevel converters for compensating harmonics and zero sequence in three-phase four-wire systems with neutral is presented. The low computational cost of the proposed method is always the same and it is independent of the number of levels of the converter. The conventional two-dimensional (2-D) space vector algorithms are particular cases of the proposed generalized modulation algorithm. In general, the presented algorithm is useful in systems with or without neutral, unbalanced load, triple harmonics and for generating 3-D control vectors. 相似文献
7.
Novel algorithms for the multirate and fast parallel implementation of the 2-D discrete Hartley transform (DHT)-based real-valued discrete Gabor transform (RDGT) and its inverse transform are presented in this paper. A 2-D multirate-based analysis convolver bank is designed for the 2-D RDGT, and a 2-D multirate-based synthesis convolver bank is designed for the 2-D inverse RDGT. The parallel channels in each of the two convolver banks have a unified structure and can apply the 2-D fast DHT algorithm to speed up their computations. The computational complexity of each parallel channel is low and is independent of the Gabor oversampling rate. All the 2-D RDGT coefficients of an image are computed in parallel during the analysis process and can be reconstructed in parallel during the synthesis process. The computational complexity and time of the proposed parallel algorithms are analyzed and compared with those of the existing fastest algorithms for 2-D discrete Gabor transforms. The results indicate that the proposed algorithms are the fastest, which make them attractive for real-time image processing. 相似文献
8.
《IEEE transactions on image processing》2009,18(12):2790-2796
9.
10.
Efficient 2-D based algorithms for WLS designs of 2-D FIR filters with arbitrary weighting functions
The impulse response coefficients of a two-dimensional (2-D) finite impulse response (FIR) filter naturally constitute a matrix. It has been shown by several researchers that, two-dimension (2-D) based algorithms that retain the natural matrix form of the 2-D filter’s coefficients are computationally much more efficient than the conventional one-dimension (1-D) based algorithms that rearrange the coefficient matrix into a vector. In this paper, two 2-D based algorithms are presented for the weighted least squares (WLS) design of quadrantally symmetric 2-D FIR filters with arbitrary weighting functions. Both algorithms are based on matrix iterative techniques with guaranteed convergence, and they solve the WLS design problems accurately and efficiently. The convergence rate, solution accuracy and design time of these proposed algorithms are demonstrated and compared with existing algorithms through two design examples. 相似文献
11.
微波大功率变脉冲放大器的研制 总被引:1,自引:0,他引:1
针对基于悬浮平台微波凝视关联成像系统对变脉冲宽度和大峰值功率的需求,研制了一款 X 波段变脉冲固态功率放大器。描述该放大器组件中高速漏极调制及保护电路和射频开关的实现方案,分析大功率高速漏极调制电路输出电压脉冲的影响因素,优化调制电路的负载设计,并解决功放输出射频脉冲的包络凹陷问题。经试验验证:研制的功率放大器具有散热性好,稳定工作时间长,最窄脉宽 20 ns,上升下降沿均小于 3 ns,峰值功率大于 40 W 的射频脉冲输出等特点;其漏极调制电路输出 24 V电压脉冲,上升沿小于 20 ns,下降沿约 60 ns。 相似文献
12.
《IEEE transactions on image processing》2006,15(11):3375-3384
In the tensor representation, a two-dimensional (2-D) image is represented uniquely by a set of one-dimensional (1-D) signals, so-called splitting-signals, that carry the spectral information of the image at frequency-points of specific sets that cover the whole domain of frequencies. The image enhancement is thus reduced to processing splitting-signals and such process requires a modification of only a few spectral components of the image, for each signal. For instance, the$alpha$ -rooting method of image enhancement can be fulfilled through processing separately a maximum of$3N/2$ splitting-signals of an image$(Ntimes N)$ , where$N$ is a power of two. In this paper, we propose a fast implementation of the$alpha$ -rooting method by using one splitting-signal of the tensor representation with respect to the discrete Fourier transform (DFT). The implementation is described in the frequency and spatial domains. As a result, the proposed algorithms for image enhancement use two 1-D$N$ -point DFTs instead of two 2-D$Ntimes N$ -point DFTs in the traditional method of$alpha$ -rooting. 相似文献
13.
Shlager K.L. Maloney J.G. Ray S.L. Peterson A.F. 《Antennas and Propagation, IEEE Transactions on》1993,41(12):1732-1737
A comparison of the accuracy of several orthogonal-grid finite-difference-time-domain (FDTD) schemes is made in both two and three-dimensions. The relative accuracy is determined from the dispersion error associated with each algorithm and the number of floating-point operations required to obtain a desired accuracy level. In general, in both 2-D and 3-D, fourth-order algorithms are more efficient than second-order schemes in terms of minimizing the number of computations for a given accuracy level. In 2-D, a second-order approach proposed by Z. Chen et al. (1991) is much more accurate than the scheme of K.S. Yee (1966) for a given amount of computation, and can be as efficient as fourth-order algorithms. In 3-D, Yee's algorithm is slightly more efficient than the approach of Chen et al. in terms of operations, but much more efficient in terms of memory requirements 相似文献
14.
三相全桥PWM电压源整流器(VSR)是一种优质的升压型四象限AC·DC变换器,能够输出稳定的直流电压和获得可调的输入电流位移因数。在许多应用领域中.对三相电压源整流器的整体效率要求日益提高。考虑到三相电压源整流器的开关损耗与调制算法密切相关.为此需要改进已有的调制算法.本文在理论上推导了电压源整流器多解性原理基础上.分析了传统SPWM和SVPWM算法的本质联系.提出了一种在三相电压源整流器目标函数中注入零序分量的最小开关损耗SPWM和SVPWM调制算法.并推导了功率器件的功耗计算公式。在利用MATLAB/SIMULINK对采用最小开关损耗SPWM和SVPWM调制算法的整流器进行仿真分析之后,采用DSP F28335实现了最小开关损耗PWM调制算法的电压源整流器实验平台.验证了有关结论。相比传统的SPWM和SVPWM调制算法.最小开关损耗PWM算法能够将整流电路提升效率2~3% 相似文献
15.
Noncoherent multiuser detection for nonlinear modulation was previously studied and the idea of phase-independent noncoherent decorrelation was introduced and three post-decorrelative detectors were obtained and analyzed. However, their implementation requires the knowledge of the signature waveforms of all the users, which may be available only for centralized implementation. In this paper, we obtain a blind adaptive noncoherent decorrelative detector for nonlinear modulation that is suitable for distributed implementation with the knowledge of only the normalized signals of the desired user and the additive noise variance. This detector is based on the stochastic approximation method and does not require the overhead of any kind of "training." Two adaptive algorithms are developed, one guided by every signal in the desired user's signal set individually, and the other by the user's entire signal space. While this paper focuses on the particular problem of blind adaptive noncoherent decorrelative detection, it addresses a more general adaptation issue, namely, that of improving the convergence properties of an adaptive scheme by effectively using all the information that is known, and adapting only to the part of the desired solution that is truly unknown. Convergence is shown in the mean squared error sense for both the fixed step-size and time-varying step-size versions of the two algorithms. 相似文献
16.
三相全桥PWM电压源整流器(VSR)是一种优质的升压型四象限AC-DC变换器,能够输出稳定的直流电压,获得可调的输入电流位移因数。在许多应用领域中,对三相电压源整流器的整体效率要求日益提高。考虑到三相电压源整流器的开关损耗与调制算法密切相关,为此需要改进已有的调制算法。本文在理论上推导了电压源整流器多解性原理基础上,分析了传统SPWM和SVPWM算法的本质联系,提出了一种在三相电压源整流器目标函数中注入零序分量的最小开关损耗SPWM和SVPWM调制算法,并推导了功率器件的功耗计算公式。在利用MATLAB/SIMULINK对采用最小开关损耗SPWM和SVPWM调制算法的整流器进行仿真分析之后,采用DSP TMS320F28335实现了最小开关损耗PWM调制算法的电压源整流器实验平台,验证了有关结论、相比传统的SPWM和SVPWM调制算法,最小开关损耗PWM算法能够将整流电路提升效率2~3%。 相似文献
17.
F. de S. Chaves F. R. P. Cavalcanti R. A. de Oliveira Neto R. B. Santos 《Wireless Communications and Mobile Computing》2010,10(2):200-213
This paper presents a class of distributed power control algorithms for wireless networks which provides quality of service (QoS) fulfillment by exploiting the channel variability opportunistically. It is suitable for traffic sources requiring either a minimum or a prescribed QoS provision, and at the same time provides a fair resource allocation. Practical system constraints such as limitations on transmission power and modulation and coding schemes are considered in this framework. Moreover, it is analytically shown to be more energy efficient than the opportunistic power control. Two algorithms of this class are described and have their performance confronted with opportunistic algorithms. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
18.
《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(9):4081-4106
19.
空间调制(Spatial Modulation,SM)是一种特殊的多天线传输技术,利用发送天线索引和发送的符号共同传递信息.为了获得发送分集增益,人们将天线选择技术应用到SM系统中,提高SM系统解调性能.在天线选择技术中,最大-最小欧式距离(Euclidean Distance Antenna Selection,EDAS)准则应用较为广泛,但是它的全搜索求解方法复杂度高,限制了其应用.为此,本文利用空间调制系统和调制符号本身的特性,从2维量化解调的视角出发,给出了两种低复杂度的最优天线选择算法,并通过计算机仿真和复杂度分析,表明了该算法的有效性和最优性. 相似文献
20.
Monitoring of polyethylene wear in nonmetal-backed acetubular cups by digitized anteroposterior pelvic radiography 总被引:1,自引:0,他引:1
Sarry L Tilmant C Boisgard S Boire JY Levai JP 《IEEE transactions on medical imaging》2003,22(9):1172-1182
The aim of this study was to assess polyethylene wear in a total hip prosthesis by digitized radiography of the whole pelvis in the anteroposterior (AP) plane. The three-dimensional (3-D) pose of the nonmetal-backed acetubular cup, materialized by its metal ring and the femoral head made of metal or ceramic, was estimated using iterative algebraic algorithms with inner bias correction and bootstrapping for variance reduction. Points of interest were obtained by maximizing the correlation between sampled density profiles and 3-D geometric models degraded by the modulation transfer function (MTF) of the radiographic system and the film scanner. The error in the maximal correlation estimate were inferred from noise power spectra (NPS) and allowed the calculation of the point covariance matrix. Both NPS and MTF were modeled for each stage and estimated using least-square fitting of the overall NPS model to the autospectral density function calculated in stationary regions. Comparison of the radiographic time series was made possible by the high accuracy level and 3-D matching from the cup orientation. The feasibility of the full 3-D measurement, the assumption of negligible lateral wear and its influence on AP wear are discussed on simulated and real radiographic data. 相似文献