Table of Content

20 August 2010 Volume 37 Issue 4

  

Original Articles

Double thresholds opportunistic transmission strategy in the MU-MIMO downlink with limited feedback

LI Zhao;YANG Jia-wei;ZHAO Lin-jing

J4. 2010, 37(4):  581-586.  doi:10.3969/j.issn.1001-2400.2010.04.001

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We introduce a double thresholds opportunistic transmission scheme in the multiuser MIMO downlink with limited feedback. In the strategy two thresholds are employed. In each time slot the mobile station (MS) whose channel gain exceeds the primary threshold is eligible for feeding back information and becomes the candidate which could be scheduled by the base station (BS). The secondary threshold is derived from the primary one and used for MS's transmission mode selection, including beamforming (BF) and spatial multiplexing (SM). With feedback information, the BS schedules one user out of candidate MSs. Theoretical analysis in company with Monte-Carlo simulation are employed. Results show that the scheme can effectively reduce the feedback load, achieve high system capacity and good outage performance.

High performance EBCOT algorithm and VLSI architecture

LIU Kai;LI Yun-song;GUO Jie

J4. 2010, 37(4):  587-593.  doi:10.3969/j.issn.1001-2400.2010.04.002

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We propose an efficient coding algorithm and architecture composed of the bit plane-parallel and pass-parallel coder with efficient zero coefficients detection for EBCOT entropy encoder used in JPEG2000.After the detailed analysis of wavelet coefficients' precision and distribution in JPEG2000, there are three main modes of zero coefficients in the wavelet domain, i.e., zero column, zero stripe and zero code block. And we also discover that the coding information on each bit plane and the corresponding passes can be obtained simultaneously in the hardware structure. Therefore, bit plane-parallel and pass-parallel coding with zero detection (BPPP-ZD) is proposed, and its VLSI architecture is shown in detail. Analysis and the corresponding software/hardware experimental results show that the proposed architecture reduces the processing time greatly compared with other architechures, and a prototype chip is synthesized which can process 1024×1024 gray level images with 79 frames per second at the working frequency of 79.466MHz.

Effective strategy for terminal reconfiguration under the framework of IEEE 1900.4

ZHANG Wen-zhu;ZENG Ye;SUN Xiao-yan

J4. 2010, 37(4):  594-601.  doi:10.3969/j.issn.1001-2400.2010.04.003

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The strategy of reconfiguration for a multimode reconfigurable terminal plays an important role in ensuring the quality of service (QoS) in cognitive radio networks. An effective strategy for terminal reconfiguration is presented under the framework of IEEE 1900.4 in this paper. The proposed strategy combines the eigenvector method and the modified TOPSIS (technique for order preference by similarity to ideal solution), which can rank the available reconfiguration mode alternatives with fast and simple implementation. At the same time, it can provide the user with the best available QoS. Simulations are conducted in a cognitive radio network comprised of UMTS, WiMAX and WLANs. The results show that the strategy can effectively decide the optimum mode of reconfiguration by making trade-offs among network conditions, user preference, and service applications.

Multipath rejection of radar ESM signals based on the time-varying AR model

LI Lin;JI Hong-bing;SHI Yin-shui

J4. 2010, 37(4):  602-607.  doi:10.3969/j.issn.1001-2400.2010.04.004

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Usually, there is multipath interference in radar ESM signals, which will influence the correctness of feature extraction and emitter recognition. A multipath rejection method based on the time-varying AR model is proposed in this paper. First, the nonlinear energy operator method is used for the approximate estimation of multipath time delay. Then the time-varying AR model based on the time function is used for sequence prediction. And the precise multipath time delay and amplitudes factor are obtained by the LS method, on the basis of which a stepwise rejection method is proposed for the multipath signal filtering. Finally, experiments on simulation and actual radar emitter signals verify the correctness and efficiency of the proposed method for multipath rejection.

Double-loop control one cycle PFC converter high-level model and its circuit realization

LI Ya-ni;YANG Yin-tang;ZHU Zhang-ming

J4. 2010, 37(4):  608-612.  doi:10.3969/j.issn.1001-2400.2010.04.005

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To simplify the design process and increase power efficiency, using Simulink's topology and linearization method, a high-level model of the one-cycle boundary controlled power factor correction (PFC) boost converter is described based on the double-loop dynamic transfer control function. The voltage loop provides low frequency stability for low total harmonic distortion(THD), and the current loop improves high frequency dynamic characteristic. According to this system model, the transistor level PFC converter is realized and verified using the Sinomos 1.0μm 40V CMOS process. Measured results show that the power factor correction is 0.988, that THD is 3.8％, and that the stable operating current is 2.43mA at the simulation of V_DD=15V, V_INV=2V, and V_ZCD=2V. The double-loop control system would achieve the one cycle control mode efficiently, and improve the system stability and dynamic response speed, which displays the high-performance characteristics of the power management chips.

Semantic color extraction and semantic shot segmentation for soccer video

NIU Zhen-xing;LI Jie;GAO Xin-bo

J4. 2010, 37(4):  613-618.  doi:10.3969/j.issn.1001-2400.2010.04.006

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Based on the color feature analysis, this paper considers the shot segmentation issue from the perspective of semantic analysis, i.e., the semantic shot segmentation. In most prior works they segment and classify the shot by using the dominant color of the field for soccer video, which can not properly utilize the plenty of color information on sports video. In this paper, we expand one dominant color in to several semantic colors, and define the Color Ratio Feature (CRF). Then, the Support Vector Machine (SVM) framework is used for shot classification. The precision of shot classification shows that the color ratio feature is useful to improve the performance. Further, considering the temporal variations in the semantic color due to environment, this paper gives an adaptive semantic color extraction algorithm, and we evaluate the influence of classification precision on the number of semantic colors.

Optimal joint MMSE DFE transceivers for amplify-forward MIMO relay systems

LI Chuan;LIU Wei;LI Jian-dong;ZHOU Li-hua

J4. 2010, 37(4):  619-623.  doi:10.3969/j.issn.1001-2400.2010.04.007

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An optimal Joint MMSE decision feedback equalization (DFE) aided transceiver of amplify-and-forward (AF) relay-assisted MIMO systems is designed. Specifically, the linear processing matrix at the base station, the linear weighting matrix at the relay station and the nonlinear receiver consisting of the feedforward processing matrix and feedback processing matrix at the mobile station are jointly designed using the criteria of the minimum mean square error (MMSE). Compared with the existing joint linear MMSE benchmarker transceiver, for the BER of less than 10-3, our joint MMSE DFE transceiver has a performance gain of over 10dB.

Layer-based precoding scheme for the multi-cell MIMO system

HAO Dong-lai;GE Jian-hua

J4. 2010, 37(4):  624-629+654.  doi:10.3969/j.issn.1001-2400.2010.04.008

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A new layer-based precoding scheme is presented in multi-cell Multiple-Input Multiple-Output (MIMO) systems. Based on the traditional precoding algorithm, a layered precoding method is adopted in the intra and inter-cell separately. By means of the game theory and the concept of signal leakage noise rate, a precoding weights selection criteria and methods in each layer are also proposed. The scheme can obtain an interference suppression effect for multi-users in the multi-cell system. Simulation results show that the proposed algorithm, with low computational complexity, provides improvement over existing schemes.

Design and implementation of the FFT parallel processor based on ASIP

ZHANG Li;LI Shuang-fei;SHI Guang-ming;LI Fu

J4. 2010, 37(4):  630-635.  doi:10.3969/j.issn.1001-2400.2010.04.009

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The ASIP combines programmability of DSP and high speed of ASIC, and the parallel array processing system based on it plays an important role in the high-speed and real-time processing applications. An implementation of 1024 points FFT parallel processor based on the ASIP is presented in this paper. An ASIP with the reduced instruction set computer (RISC) architecture is designed as the processing element (PE), which constructs the kernel of the parallel processing system. In addition, the communication matrix is adopted to achieve the data exchange between PEs. Experimental results show that, compared with the typical DSP, the new proposed architecture improves the processing speed by 30％. Furthermore, this system has the advantages of larger parallel scale, greater function adaptability, relatively lower designing complexity and greater design reuse ability. So it can be achieved in a single FPGA in the form of SoC.

Passive multi-target tracking based on independent particle filtering and fuzzy clustering

ZHANG Jun-gen;JI Hong-bing

J4. 2010, 37(4):  639-641.  doi:10.3969/j.issn.1001-2400.2010.04.010

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A novel method based on fuzzy clustering and independent particle filtering is proposed for nonlinear multi-target tracking. Firstly, the association of target with measurement is carried out by the use of the maximum entropy fuzzy clustering. Then the joint association probability matrix is reconstructed by utilizing the fuzzy membership degree of the target and measurement. Since particle filtering performs well in the nonlinear tracking system, this paper employs it and the joint association innovations to update each target state independently. Finally, the proposed method is applied to multi-sensor multi-target bearings-only tracking. Simulation results show that the method can obtain a higher tracking precision than JPDAF and MEF-JPDAF.

Immune optimization algorithm based on the social network searching model

SUN Yi-fei;JIAO Li-cheng

J4. 2010, 37(4):  642-647.  doi:10.3969/j.issn.1001-2400.2010.04.011

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Based on the effective information searching and transmission ability of the social network, a novel immune optimization algorithm, named the Immune Optimization Algorithm based on the Social Network Searching Model (SNSIA), is proposed. The new algorithm considers the settling of optimization problem as the process of information transmission. It constructs the evolutionary process by the modeling method of classical social network searching model known as the Kleinberg network model. The new individual is introduced into the antibody population via short-range and long-range connections with the aid of the network's structure growth mechanism. The probability of long-range connection would adjust adaptively when the searching reaches a certain degree, which would avoid the local optimum effectively and find the global optimum at last. The new algorithm introduces the short-range and long-range connections which take full advantage of the population's structure info, and it quickens the speed of convergence. At the same time, it brings down the probability of getting in the local optima. In experiments, the SNSIA is tested on the complex functions and compared with the particle swarm algorithm, the clonal selection algorithm and other optimization methods. Theoretical analysis and experimental results indicate that the SNSIA could maintain the solution's diversity better with a high convergence rate, and that it is also an effective and robust technique for optimization.

Blind multi-user detector based on linear prediction for DS-UWB systems

KANG Xiao-fei;YANG Jia-wei

J4. 2010, 37(4):  648-654.  doi:10.3969/j.issn.1001-2400.2010.04.012

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A blind multi-user detection algorithm based on linear prediction is proposed for the direct sequence ultra-wideband (DS-UWB) system to provide resistance to multiple access interference (MAI) and inter symbol interference (ISI). The algorithm first applies linear transformation and linear prediction on the received data, in order to suppress MAI, and then estimate and equalize the channel by Singular Value Decomposition (SVD) of the prediction error correlation matrix. According to the simulation results with the IEEE 802.15.3a UWB channel model, the proposed algorithm exhibits reasonably good performance and near-far resistance in multiuser environment compared with the conventional Rake receiver and blind MMSE receiver.

Fast passive data association algorithm base on the random set particle filter

YANG Bai-sheng;JI Hong-bing;GAO Xiao-dong

J4. 2010, 37(4):  655-659.  doi:10.3969/j.issn.1001-2400.2010.04.013

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Multiple-target tracking based on passive measurements with clutters is a difficult problem. Multiple-senor centralized fusion scheme and paticle filter(PF)implementation for the probability hypothesis density(PHD)filter are combined to tracke multiple targets effectively. Furthermore, to sovle the incapablity of the PHD filter in maintaining the integrated trajectory of each traget, the PHD recursion is implemted in parallel, where each target is tracked with a single PF. A fast data association algorithm is deducted, in which the clustering for all particles is avoided. Simulation results show that, compared with the conventional ones, the new method can keep each tracks better without additonal computational costs. Especially, when targets cross each other, the respective trajectories can be distinguished effectively.

Coherent single range doppler interferometry based space debris radar image

LIU Ya-bo;ZHANG Lei;XING Meng-dao;BAO Zheng

J4. 2010, 37(4):  660-664+670.  doi:10.3969/j.issn.1001-2400.2010.04.014

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For space debris radar imaging with the dimension smaller than the radar range resolution, with the assumption that the translational motion is compensated, and considering movement features of space debris, a novel coherent single range Doppler interferometry (CSRDI) imaging algorithm is proposed, which utilizes the intensity and the phase distribution characteristic of the signal time-frequency spectrum, and implements coherent integration via sinusoid searching. Thus the high resolution 2D space distribution of a space debris is acquired. In addition, a detailed analysis of the relation between the time-frequency spectrum and the resolution as well as the quality of the image is made, and a standard for determining the window function is proposed. Numeric simulation verifies that an image with much finer resolution and higher quality can be achieved through the proposed approach, even under a low signal to noise rate (SNR) condition.

Adaptive step by step combination cooperative spectrum sensing in cognitive radio systems

DING Han-qing;YANG Jia-wei;ZHAO Zhi-yuan

J4. 2010, 37(4):  665-670.  doi:10.3969/j.issn.1001-2400.2010.04.015

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Based on equal gain combination cooperative spectrum sensing, an adaptive step by step combination cooperative spectrum sensing in cognitive radio (CR) network is proposed. With the change of the Signal-to-Noise Ratio received by CR users, this algorithm can adjust automatically the number of CR users which participate in cooperative spectrum sensing in order to decrease the data overhead produced by spectrum sensing in the cognitive radio network. The formula for computing the average data magnitude from the CR users to the central controller over Rayleigh channels is acquired. Theoretical analysis and simulation results show that the method reduces the average data overhead from the CR users to the central controller under the same detection performance compared with the conventional equal gain combination cooperative spectrum sensing.

Target altitude measurement of bistatic MIMO radar using the virtual elements technique

JIN Ming;LI Jun;LIAO Gui-sheng;LI Wei-ping

J4. 2010, 37(4):  671-675.  doi:10.3969/j.issn.1001-2400.2010.04.016

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A target altitude measurement method using the virtual elements technique of bistatic multiple-input multiple-output (MIMO) radars is proposed. The method carries out altitude measurement by estimating the angles of targets with respect to the transmitting and receiving arrays. Different from the conventional altitude measurement method of bistatic radars, the proposed method requires neither time synchronization nor communication between transmitting and receiving ends. Hence, the proposal simplifies the configuration of the system. In addition, the angles can be paired automatically when multiple targets exist, and then target ghosts are avoided. Finally, computer simulations validate the proposed method.

High azimuth resolution wide swath imaging based on the intrapulse spotlight SAR

WU Qi-song;XING Meng-dao;LIU Bao-chang;BAO Zheng

J4. 2010, 37(4):  676-682+699.  doi:10.3969/j.issn.1001-2400.2010.04.017

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With respect to the contradiction between high resolution and wide swath, the intrapulse spotlight synthetic aperture radar (SAR) mode is presented to achieve high azimuth resolution wide swath imaging. Firstly, the model of intrapulse spotlight SAR is established, and then the characteristic of echoes in this mode is analyzed in detail. The conclusion that the intrapulse scanning can make scatterers in the different azimuth sub-scene ambiguous are given. The degrees of freedom along the elevation direction are used to resolve the range ambiguities. Meanwhile we analyze the impact of the fluctuating terrain on the imaging result. In the intrapulse spotlight SAR mode, the long synthetic aperture acquired by the intrapulse scanning technique can realize the high azimuth resolution. Meanwhile a low pulse repetition frequency (PRF) is adopted to achieve a wide swath. Therefore high azimuth resolution wide swath imaging can be achieved by intrapulse spotlight SAR mode. Results of simulation show the effectiveness of this method.

Block based iterative linear prediction at the decoder for hyper-spectral imagery compression using distributed source coding

WU Xian-yun;LI Yun-song;WU Cheng-ke;KONG Fan-qiang;LI Wen-ming

J4. 2010, 37(4):  683-688.  doi:10.3969/j.issn.1001-2400.2010.04.018

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Based on the analysis of the hyper-spectral images, a new compression algorithm based on the DCT transform domain distributed source coding is proposed. Our algorithm performs the bitplane encoding at the encoder with the DCT subbands order, while using the key frame to reconstruct the side information for LDPC decoding at the decoder. Few pixels are adopted to perform linear prediction at the encoder, thus reducing the complexity. Subbands previously decoded are utilized for iterative linear prediction based on blocks at the decoder, and following subbands are decoded with optimized side information. Compared with conventional algorithms, the proposed algorithm efficiently reduces the cost of computation and memory usage at the encoder, which facilitates the hardware implementation.

Novel method for designing DFT modulated filter banks

JIANG Jun-zheng;WANG Xiao-long;SHUI Peng-lang

J4. 2010, 37(4):  689-693.  doi:10.3969/j.issn.1001-2400.2010.04.019

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A design algorithm is proposed based on the bi-iterative scheme, due to the difficulty of designing the discrete Fourier transform (DFT) modulated filter bank. The design of the filter bank is formulated as an unconstrained optimization whose objective function is the weighted sum of the transfer distortion and the stopband energy of the prototype filters(PFs). Since the objective function is a bi-quadratic function of analysis and synthesis PFs, the optimization problem can be efficiently solved by using the bi-iterative scheme. At each iteration, one of the PFs is fixed and the other can be solved analytically. Numerical examples show that the computational cost of the proposed method is lower than that of the traditional method. Furthermore the transfer distortion of the filter bank obtained by the proposed method is approximately 16dB lower than that of the filter bank designed by the traditional method and the improvement on the reconstruction error is about 1dB.

Transmission line model and crosstalk analysis of non-ideal interconnect

DING Tong-hao;LI Yu-shan;ZHANG Wei;QU Yong-zhe;YAN Xu

J4. 2010, 37(4):  694-699.  doi:10.3969/j.issn.1001-2400.2010.04.020

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The transmission matrix for return path discontinuity is introduced to the transmission matrix model of ideal interconnect, and a new model is presented. Compared with the S-parameter model, the performance of the new model is verified and the accurate coupling crosstalk noise of non-ideal interconnect can be obtained. Finally, the influence of cutout on crosstalk is also studied. Simulation results show that the transmission lines should be placed close to the edge of cutout and that the space between two lines should be as large as possible.

Improved cycle elimination algorithm for construction of QC-LDPC codes

CUI Jun-yun;BAI Bao-ming;GUO Xu-dong

J4. 2010, 37(4):  700-704.  doi:10.3969/j.issn.1001-2400.2010.04.021

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A novel construction algorithm for quasi-cyclic low-density parity-check codes is proposed, with which we can obtain the improved girth of the corresponding Tanner graph by generalizing Yang et al.'s constraint for any cycle detected in the base matrix to detect and break the cycles in the parity check matrix. Compared with the existing cycle elimination (CE) algorithm, a better error performance can be achieved and cycle-8 free. Simulation results show that the proposed algorithm for constructing the irregular LDPC code of rate 1/2 achieves the performance of codeword error rate of 2×10^-6 at E_b/N₀=1.5dB with 80 iterations by the belief-propagation decoding algorithm.

The construction algorithm of bipartite graphs for a type of capacity-approaching LDPC erasure codes

MU Jian-jun;JIAO Xiao-peng;CAO Xun-zhi

J4. 2010, 37(4):  705-709.  doi:10.3969/j.issn.1001-2400.2010.04.022

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Tornado code is an important kind of low-density parity-check codes. It is shown that the Heavy-Tail/Poisson sequence is capable of achieving the capacity of the binary erasure channel. The construction algorithm for random bipartite graphs in the design of Tornado codes is proposed in this paper. By analyzing the distribution of Heavy-Tail/Poisson degree sequences of Tornado codes, a parameter-selection rule used to design Tornado codes is presented. Simulation results show the correctness of the parameter-selection rule. The construction algorithm for random bipartite graphs and the parameter-selection rule presented will be helpful in the design and its engineering application of Tornado codes.

Parameter estimation of hybrid DS/FH spread spectrum signals based on the S transform

ZHU Ming-zhe;JI Hong-bing

J4. 2010, 37(4):  710-715+750.  doi:10.3969/j.issn.1001-2400.2010.04.023

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This paper addresses a new method for parameter estimation of hybrid DS/FH_BPSK signals based on a time-frequency(TF) technique known as the S transform(ST). Good performance is achieved by three stages. Firstly, a nonlinear process is used to produce the reference signal(RFS) which has the same hop parameter as the original signal and its frequencies could be estimated by the cyclic spectrum as the modification information. Then the S transform is improved by adding a Gaussian window width parameter to realize the adaptation of its time-frequency resolution and the ridge curve of ST is extracted as the instantaneous frequency of RFS. Finally, the modification information is used to reduce the estimation error in the high frequency region caused by noise. Simulation results show that the proposed method can operate effectively for hop parameter estimation. Since no prior knowledge of signals is needed, the proposed method is easily implemented in a reconnaissance receiver.

Simple UWB-TOA estimation method

XIONG Hai-liang;WANG Jun;TIAN Hong-xin;YANG Hong;YI Ke-chu

J4. 2010, 37(4):  716-721.  doi:10.3969/j.issn.1001-2400.2010.04.024

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We propose a novel UWB-TOA estimation method. High-precision sample recovery is achieved using the polyphase filter, overcoming the shortcomings of the traditional method which needs the sampling data speeds up to tens of GHz to achieve high-precision positioning, conquering the bottlenecks of AD-chip hardly implemented, and the FPGA chips fail to receive and deal with such a large number of high-speed sampling data. The proposed scheme has laid a foundation of implementation and market development of UWB positioning chips. Theoretical analysis and simulation show that the proposed scheme can achieve precise positioning in short distances, that the location error can reach the centimeter level, and that the computational complexity is largely reduced compared with the coherent detection TOA estimation.

Improved iterative non-local means filter for image denoising

FENG Xiang-chu;HAO Bin-bin;ZHU Jian-guang

J4. 2010, 37(4):  722-725+736.  doi:xcfeng@mail.xidian.edu.cn

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An iterative non-local means filter for image denoising is proposed. For the proposed method, the computation of weights depends on the updated image, and for each iteration the weighted averaging is performed over the updated image. This avoids the problems that the edge of the image is blurry and that the image is not clear, which are caused by the disagreement of the computation of the weight coefficients and the computation of the averaging. The max-min principle is also guaranteed for the proposed iterative non-local means filter. Numerical examples illustrate that the proposed method removes noise well while preserving image edges and fine details.

Optimizing both radiation and scattering characteristics of the array antenna utilizing PSO

ZHANG Shuai;GONG Shu-xi;LU Bao;LING Jin;ZHA Feng-tao

J4. 2010, 37(4):  726-730.  doi:10.3969/j.issn.1001-2400.2010.04.026

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In a way the similar to the radiation pattern multiplication theorem, this paper derives that the radar cross section(RCS) of an array is the product of the array RCS factor multiplying the element RCS factor. Based on these two formulas, the method for synthesizing both desired radiation and scattering patterns by optimizing the element placement is proposed. In order to verify its validity, the method is used to minimize the peak sidelobe level (PSLL) of both the radiation and scattering patterns. Compared with the uniform array, the PSLL of both the optimized radiation and scattering pattern are considerably reduced by optimization.

Rainbow angle analysis of a homogeneous spheroid

LI Xiang-zhen;HAN Xiang-e

J4. 2010, 37(4):  731-736.  doi:10.3969/j.issn.1001-2400.2010.04.027

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A general ray-tracing method for homogeneous spheroids with the arbitrary aspect-ratio is presented on the basis of geometrical optics, and is employed to study the primary rainbow angle of spheroids with a larger aspect-ratio at an arbitrary incidence. For the prolate spheroid normally illuminated by plane waves, when the aspect-ratio is in a certain range, no primary rainbow angle exists. The research shows that the aspect-ratio range increases with the refractive index of the spheroid. For the oblique incidence, the symmetry of two primary rainbow angles varies with the tilt angle of the incident plane wave in (0°~360°). The primary rainbow angle of the oblate spheroid at the normal incidence is similar to that of the sphere. For the oblique incidence, the variation of the primary rainbow angle of oblate spheroid is opposite to that of the prolate spheroid. The results lay the theoretical groundwork for granularity measurement of the spheroidal particle.

Free search algorithm with the variable neighbourhood and step

LI Tuan-jie;CAO Yu-yan;SUN Guo-ding

J4. 2010, 37(4):  737-742.  doi:10.3969/j.issn.1001-2400.2010.04.028

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To overcome the problem of population-based optimisation algorithms-free search (FS) to find the best solution with the low efficient later stage, especially multi-dimensional search space, FS with the variable neighbourhood and step method is proposed. The previous neighbourhood space and step do not change much in searching for the overall situation and change relatively greatly in the later stage in local exploration by the algorithm. The methods for the varying neighbourhood and step are given and simulation results with four traditional functions show that the algorithm has a better probability of finding the global optimum and mean best value, with quick convergence and high precision, especially for the multi-dimensional and multimodal function.

Cyclostationarity based cascaded space-time anti-jamming processor designed to appeal to GPS receivers

SHI Bin-bin;CHENG Zhu;Qian Lin-jie;HUANGFU Kan

J4. 2010, 37(4):  743-750.  doi:10.3969/j.issn.1001-2400.2010.04.029

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In order to reduce the computational burden of space-time processing filter groups, a space-time processing filter groups designed method is proposed. This method can be easily implemented owing to low computational complexity and modular structures. Under the strong jamming scenario a cascaded space-time adaptive processing scheme is deviced with its first stage as ordinary space-time adaptive processing with a certain constraint and the second stage as the beam former aided with information extracted from the cyclic-covariance matrix. Experiments show that such a cascaded scheme could bring signal-to-noise-ratio improvement for the space-time processing.

Novel IR target tracking method based on the  grey prediction and HOGI feature

ZHANG Qi;CAO Qi;WANG Xiao-wei;BI Du-yan

J4. 2010, 37(4):  751-757.  doi:10.3969/j.issn.1001-2400.2010.04.030

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Generally, the IR target tracking method is unable to extract the IR target's feature effectively during the process of IR target tracking. For solving this problem, a novel and robust IR target tracking method is proposed. The method adopts a Grey Model to predict the target's position firstly, and then constructs the Histogram of Oriented Gradient and Illumination (HOGI) of the candidate target area which centers on the predicted position. Finally, the method incorporates this HOGI feature into Mean Shift and realizes the precise tracking. Experimental results show that the proposed method has an excellent tracking precision. When a part or whole of the target is sheltered, the tracking goes on to make sure the target is not lost, which reflects the robustness of the method.

Channel estimation method for OFDMA systems over fast time-varying channels

LI Dan;FENG Sui-li;YE Wu;ZHUANG Hong-cheng

J4. 2010, 37(4):  758-763.  doi:10.3969/j.issn.1001-2400.2010.04.031

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Current channel estimation (CE) schemes for OFDMA systems track channel variations symbol by symbol result in ICI when the channel is Time-varying (TV) in one symbol period. However, conventional TV CE methods for OFDM systems need optimal even-pilots to track channel time variations in one symbol period. For practical OFDMA systems, the required even pilot tone is not satisfied. In this paper, we present a pilot-assisted CE method for practical OFDMA systems in TV channels, which is performed in the frequency-domain, avoiding time-domain transformations and does not need even-spaced pilots. The frequency-domain transmission function is employed to estimate channel variations over one OFDMA symbol period. Simulation results show that the proposed method outperforms current OFDMA CE schemes in terms of the symbol-error-rate (SER) and Mean Square Error (MSE).

Method of particle swarm optimization based on the chaos map

LIU Dao-hua;YUAN Si-cong;LAN Yang;MA Xin-jian

J4. 2010, 37(4):  764-769.  doi:10.3969/j.issn.1001-2400.2010.04.032

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In order to improve the solving performance of particle swarm optimization(PSO), first the basic principle of PSO is analyzed and mapping rules for two types of chaos map are given. Next, PSO based on the Logistic map (LGM-PSO) and Lozi's map (LZM-PSO) are constructed, and the methods for treating two types of constraints are given. To compare the performances of LGM-PSO, LZM-PSO and the standard particle swarm optimization, the three methods are used to solve the benchmark constrained optimal problem. Their performances are compared in terms of optimal solution, success ratio, average valid evaluation number, iterative occupancy hours and so on. Comparison results indicate that the LZM-PSO has many advantages, such as higher solution accuracy and higher computational efficiency.

Multi-sensor image fusion algorithm considering neighborhood consistency in the nonsubsampled contourlet transform domain

HUO Guan-ying;LI Qing-wu;SHI Dan

J4. 2010, 37(4):  770-776.  doi:10.3969/j.issn.1001-2400.2010.04.033

Abstract ( 1925 )   PDF (1724KB) ( 1070 )   Save

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For the fusion problem of the multi-sensor images of the same scene, a new algorithm is proposed based on neighbor energy and variance in the nonsubsampled Contourlet transform (NSCT) domain. Source images are firstly decomposed in the NSCT domain. For low frequency sub-band coefficients selection, the decision value of variance and energy based on neighbor variance and average neighbor energy is constructed for each pixel, and the rule based on the maximum of the decision value is adopted, so as to keep both image luminance and image details. For band-pass directional sub-band coefficients selection, the rule of maximum neighbor energy is used to keep more edge information. Finally the fused image is obtained through inverse transform. The algorithm has been used to merge multi-focus images and also infrared and visible light images. Experimental results indicate that the proposed method avoids the introduction of artifacts, with better edge details and luminance information, so that the fused image has a better subjective visual effect and objective evaluation criteria.