Table of Content

20 April 2009 Volume 36 Issue 2

  

Original Articles

New method for solving the ambiguity of the radial velocity of a moving target


YANG Lei;WANG Tong;BAO Zheng

J4. 2009, 36(2):  189-192. 

Abstract ( 2099 )   PDF (618KB) ( 1310 )   Save

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To obtain good performance for detecting a moving target, the multi-channel SAR system always utilizes a long baseline. However, the radial velocity calculated by the interferometric phase presents ambiguous solutions. A radial velocity unwrapping method for a multi-channel SAR-GMTI system has been proposed in this paper. Based on the analysis of the relationship between interferometric phase of the mover and radar system parameters, the principle that the system velocity response can be altered by the variation of the wavelength and length of the baseline is revealed. The new method utilizes both the multi-baseline and multi-frequency to unwrap the radial velocity and performs better than the routine method. Synchronously, a numerical method is proposed for computing the precise radial velocity of the mover simply but effectively. Analysis and computer simulation demonstrates the validity of the method.


Fast joint transmit-receive antenna selection algorithm for MIMO systems


JING Mei-fang;LI Xiao-hui;YI Ke-chu;HEI Yong-qiang

J4. 2009, 36(2):  193-197. 

Abstract ( 2229 )   PDF (601KB) ( 1071 )   Save

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MIMO systems with multiple antennas can cause a high cost and complexity. Focusing on this problem, a fast joint transmit-receive antenna selection algorithm is presented. The proposed algorithm uses the Gerschgorin circle theorem to estimate the eigen-values, and choose the row and column whose lower bound of the minimum eigen-value is the max by searching for the matrix row by row and column by column, so the minimum eigen-value of matrix declines to the least. Theoretical analysis and simulation results show that the capacity of the proposed algorithm is close to that of the optimal exhaustive search algorithm with low complexity in the case where the number of RF chains is small.


Threshold selection relaying scheme for coded cooperation


HAN Chun-lei;GE Jian-hua;LIN Yi;GONG Feng-kui

J4. 2009, 36(2):  198-202. 

Abstract ( 1951 )   PDF (740KB) ( 1116 )   Save

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For the rate reduction induced by using cyclic redundancy check (CRC) in coded cooperation, an improved threshold selection relaying scheme is proposed for coded cooperation. The upper bound of the bit error rate (BER) is derived when using rate-compatible punctured convolutional codes, and an optimum threshold (OT) is obtained by minimizing the BER. The cooperative user decides whether to relay or not by comparing the estimated signal to noise ratio (SNR) with the threshold. Simulations show that with the OT and power allocation method, the scheme has a better improvement over the CRC scheme.


OFDM based precise ranging technique in space


REN Guang-liang;SUN Chui-qiang;NI Hao;CHANG Yi-lin

J4. 2009, 36(2):  203-206. 

Abstract ( 2401 )   PDF (590KB) ( 1349 )   Save

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According to the properties of OFDM in the time and frequency domains, a novel ranging method in space is proposed. The coarse estimation of range can be obtained from the correlation of the waveforms of OFDM signals in the time domain, and the fine estimation is obtained from the phase differences between the sub-carriers in the frequency domain. The fine estimation is then adopted to correct the coarse estimation, and the final estimation of range is achieved. Simulation results show that the ranging accuracy of the proposed method is more than 4 times better than that of pseudo-code ranging. Furthermore, the ranging accuracy is close to the centimeter level when the signal-to-noise ratio is beyond 20dB.


Low complexity TOA estimation algorithm in the UWB indoor channel


XIAO Zhu1;TIAN Hong-xin1;YI Ke-chu1;YU Quan2

J4. 2009, 36(2):  207-210. 

Abstract ( 2169 )   PDF (654KB) ( 1038 )   Save

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A TOA estimation algorithm based on the strongest path detection of the UWB multipath signal in the indoor channel is proposed. The convolution operation is designed for the strongest path search to implement TOA estimation. TOA estimation need not depend on the LOS path(LP) and is suitable for NLOS(non line-of-sight), and the strongest path search has the advantage of low-complexity computation compared with LP detection due to avoiding the process of threshold setting. Through experiments using NLOS channels in IEEE 802.15.4a, the localization influence due to algorithm parameters is discussed, which proves the applicability of the proposed localization algorithm in the indoor multipath channel NLOS environment.


Low-complexity encoding and decoding algorithm for the unitary space-time scheme


JIANG Yan-ping;LI Xiao-hui;KOU Wei-dong;HUANG Zhen-hua

J4. 2009, 36(2):  211-215. 

Abstract ( 2290 )   PDF (619KB) ( 978 )   Save

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The new encoding algorithm for the unitary space-time scheme with four transmit antennas is proposed. By combining the unit matrix with the space-time block code matrix, maximum likelihood decoding at the receiver is simplified to maximum Euclidean distance decoding so that complexity for decoding is reduced greatly. On the basis of analysis on the receive SNR in the Rayleigh channel, the lower bound of the capacity is deduced. Analysis and simulation results show that full diversity gain is guaranteed by the scheme, the number of times of complex number calculation for decoding is reduced by 85.6％ while the bit error rate of this scheme is approximate to that of the maximum likelihood decoding algorithm. And the lower bound of channel capacity coincides with the one deduced theoretically.


Fast searching algorithm for the decoder of the unitary space-time modulation


WANG Jie-ling1;LIU Zu-jun1;YI Ke-chu1;YANG Hong1;2

J4. 2009, 36(2):  216-221. 

Abstract ( 1958 )   PDF (511KB) ( 1043 )   Save

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A fast searching decoder algorithm of the Unitary Space-Time Modulation is presented for the constellations created by the systematic method. The receiver creates a constellation and multiplies it with the received signal by each dimension separately. Then all the elements are added up according to a certain mode, and the receiver can get four correlations. Only by some additions and inner norms, can the new scheme save the multiplications in the Maximum Likelihood (ML) algorithm when the rotating matrix is generated and the multiplication between the rotating matrix and the base constellation, and it can also save the multiplication between the three constellations and the received signal. It is proved that the new scheme can reduce the searching scope of the ML algorithm by about 75％ without degradation of the performance.


Movement-assisted sensor network deployment algorithm for maximizing the network coverage


CUI Can1;2;SHEN Zhong1;CHANG Yi-lin1;WANG Yan-ling1

J4. 2009, 36(2):  222-227. 

Abstract ( 1566 )   PDF (969KB) ( 1020 )   Save

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We study improvement of the sensor network coverage using mobile sensors. A movement-assisted sensor deployment algorithm for maximizing the network coverage is proposed. First, the whole deployment area is divided into many small regions called grids, and the initial deployment network is represented as a bipartite graph G in which the vertex set of G can be partitioned into two sets: the set of mobile sensors and the set of grids needed to be covered. If one mobile node can cover another grid, then there is one edge between them. The cost of the movement can be measured by the movement distance, the energy consumed by the movement, or the number of flips by the node. Then, a matching of maximum cardinality of G corresponds to an optimal movement plan which maximizes the network coverage subject to minimizing the movement costs.


Novel scene adaptive method for non-uniformity correction in infrared focal plane arrays


LAI Rui;YANG Yin-tang

J4. 2009, 36(2):  228-232. 

Abstract ( 2228 )   PDF (927KB) ( 1284 )   Save

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A neural network based scene-adaptive non-uniformity correction (NUC) algorithm for infrared focal plane arrays (IRFPA) is proposed. This method redesigns the structure of the hidden layer, which is helpful to estimate the desired target value more precisely. In addition, the variable step size normalized LMS (VSS-NLMS) based adaptive filtering technique is introduced to the correction parameter estimation process, which yields faster convergence and higher stability. Anyway, the proposed NUC method achieves high performance in correction precision, convergence rate and stability, which is validated by experimental results.


New method for improving the performance of radar HRRP recognition and rejection


CHAI Jing;LIU Hong-wei;BAO Zheng

J4. 2009, 36(2):  233-239. 

Abstract ( 1966 )   PDF (631KB) ( 961 )   Save

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Multi-kernel SVDD is proposed on the basis of SVDD. Due to the disadvantage of having too simple a kernel formation, the SVDD is expanded from a single Gaussian kernel to a linear combination of multi-Gaussian kernels. The resulting multi-kernel SVDD could be expressed as an SDP problem, so it could be solved with the global optimal solution. The proposed method employs a more complicated kernel formation, which can describe the distributing boundary of training examples in high-dimension feature space more flexibly, thus leading to a much higher recognition rate and a much lower false rate than the SVDD.


Study of a post-Doppler processing STAP method


LI Cai-cai;LIAO Gui-sheng;ZHU Sheng-qi;YUAN Xiao-yi

J4. 2009, 36(2):  240-244. 

Abstract ( 2176 )   PDF (837KB) ( 951 )   Save

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In post-Doppler processing methods of space time adaptive processing (STAP) available, when the window function is not used, Doppler channels are orthogonal, and even when window function is used, the correlation between channels is not high. A new post-Doppler processing STAP method is proposed, which improves the correlation between channel of interest and auxiliary channels, reduces the degree of freedom of clutter and lightens the burden of spatial adaptive processing, by reducing their space. It can restrain clutter well and improve the 3DT method by 0.5dB. It is also highly robust to errors as high as 10％. Its validity is illustrated through experiment utilizing raw data of the airborne dual-channel radar system.


New short-range clutter suppression approach for the non-side-looking airborne radar


MENG Xiang-dong;WANG Tong;WU Jian-xin;BAO Zheng

J4. 2009, 36(2):  245-249. 

Abstract ( 1971 )   PDF (1161KB) ( 1116 )   Save

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A subarray synthesis approach with elevation filtering for the non-side-looking airborne radar is presented. This approach is firstly to filter out the near-range clutter by utilizing the elevation freedoms of the plane array, and then to do the STAP work in azimuth space and in the time domain. By so doing, the clutter homogeneous characteristic is enhanced and the covariance matrix can be evaluated easily and precisely, which improves the STAP performance for non-side-looking clutter suppression greatly. Simulation results prove that the improvement factor is enhanced roughly by 30dB when there is no system error.


Study of suppressing RF interference by range processing in the coast-ship HF surface wave SIAR


LIU Chun-bo;CHEN Bai-xiao;ZHANG Shou-hong

J4. 2009, 36(2):  250-255. 

Abstract ( 1839 )   PDF (1300KB) ( 1049 )   Save

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To suppress the RF interference in the coast-ship bistatic HF surface wave SIAR, new techniques by eigenvalue decomposition (EVD) in the range domain are developed. Ascribed to the operation mode of multiple carrier frequencies and a single reception antenna, the interference in the radar is different from the conventional ones. Based on the correlation between the fast-range samples in a sweep number, a fast-range processing technique is proposed, which estimates the interference with the eigenvector of the interference correlation matrix as the weighting coefficient and takes the interference from the raw data. Furthermore, two new methods for estimating the covariance matrix are presented as well according to the Doppler feature of the interference. The techniques can reduce the requirement of memory capacity while providing enough training samples. Experimental results show the validity of the proposed techniques by the fast-range and slow-range processing.


Frequency and DOA estimation using snapshots nearby frequency spectrum peaks in the presence of unknown sensor gains and phases error


ZENG Cao;LIAO Gui-sheng;TAO Hai-hong;ZHANG Juan

J4. 2009, 36(2):  256-262. 

Abstract ( 1957 )   PDF (860KB) ( 1123 )   Save

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A new method for frequency and direction of arrival (DOA) estimation using snapshots nearby frequency spectrum peaks is proposed for application in the multichannel system in the presence of unknown sensor gains and phase. A modified single snapshot mode for only one source contributing to a frequency spectrum peak and a weighted subspace projection for multiple sources are proposed, respectively. Without the calculation of the spatial covariance matrix and pairing operation of frequency and direction of arrival, the method is effective for both coherent and incoherent sources scenarios and may be applied in the multichannel system due to the high compress ratio of the 3dB signal bandwidth to the sampling rate. The measured data based on a uniform linear array illustrate the effectiveness for coherent sources and the robustness to gains and phases mismatch and the simulated data based on a plane array verify the higher angle resolution in comparison with the MUSIC algorithm.


Fast DOA estimation algorithm based on the multistage Wiener filter


WU Jian-xin;WANG Tong;SUO Zhi-yong

J4. 2009, 36(2):  263-268. 

Abstract ( 1875 )   PDF (567KB) ( 1119 )   Save

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A fast algorithm for direction-of-arrival (DOA) estimation is presented. By the characteristic that the mutual correlation vector of a uniform array is located in the signal subspace, a signal subspace estimation method is obtained using a multi-stage wiener filter, which avoids the known expected signal and eigen-decomposition. Then, the min-norm rooting method is adopted to realize DOA estimation. The method can estimate DOA effectively even in the case of no expected signal, and the complexity is O(NLP), where N is the number of sensors, L is the number of training sets, and P is the number of signals. Finally, simulation results are given to demonstrate the effectiveness of the method.


Image denoising using the directional property in the NSCT domain


JIA Jian1;2;JIAO Li-cheng1

J4. 2009, 36(2):  269-273. 

Abstract ( 2534 )   PDF (956KB) ( 1127 )   Save

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As the main prevailing denoising method, how the threshold function works and what the threshold value is are of the greatest importance. According to the interscale and intrascale dependencies of the coefficients in the non-subsampled Contourlet transform domain, and considering the change of coefficient’s aggregation with different directional subbands in the same scale, a novel non-subsampled Contourlet transform denoising scheme using the directional property (AD_NSCT) is proposed. This scheme can lead to enhanced estimation results for images that are corrupted with additive Gaussian noise over a wide range of noise variance. To evaluate the performance of the proposed algorithms, simulation results are compared with those by the algorithms, such as wavelet threshold, Contourlet transform threshold and non-subsampled Contourlet transform threshold for image denoising. The simulation results indicate that the proposed method outperforms the others 0.5~3.3dB in the PSNR, and keep a better visual result in edges information reservation as well.


Social cooperation based multi-agent evolutionary algorithm


PAN Xiao-ying;JIAO Li-cheng

J4. 2009, 36(2):  274-280. 

Abstract ( 1569 )   PDF (675KB) ( 978 )   Save

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A Social Cooperation based Multi-Agent Evolutionary Algorithm (SCMAEA) which integrates the social cooperation mechanism and multi-agent evolution for numerical optimization is proposed. Using the social cooperation mechanism, trust degree, which denotes the historical information for agents, is defined to control the interaction between agents. At the same time, the ‘acquaintance net model is imported to construct and update the local environment of the agent. It improves the convergence rate by the cooperation characteristic of agents. Furthermore, adopting the non-uniform mutation operation improves the searching for optimal solutions in the local region and assures the diversity of the solution. Simulation results show that compared with the multi-agent genetic algorithm, the social cooperation based multi-agent evolutionary algorithm can find the optima by a smaller number of function evaluations.


Improved microstrip directional coupler and its application


WEI Feng1;SHI Xiao-wei1;CHEN Lei2;HUANG Qiu-lin1

J4. 2009, 36(2):  281-284. 

Abstract ( 2890 )   PDF (781KB) ( 4683 )   Save

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A conventional microstrip directional coupler has an inherent drawback of poor isolation due to an unequal phase velocity between even and odd mode. To solve this problem, the technology based power canceller with the dual-stub is presented. Mismatch is induced by the dual-stub added at the Match Port of the microstrip directional coupler. Parameters adjustment of the dual-stub can change the magnitude and phase of the reflected signal from the Match Port at the RX Port, which can effectively cancel the leaked signal from the TX Port at the RX Port. A microstrip directional coupler for the UHF RFID reader with the operating frequency band of the range of 902~928MHz is proposed. The proposed directional coupler can obtain excellent isolation of -65dB and coupling of -10dB at 920MHz, effectively improve the isolation between TX and RX and decrease the size by 20％. It is successfully used in a practical UHF RFID reader.


Fast calculation of the far-field scattering from the rotationally symmetric object


ZOU Yan-lin;GUO Jing-li;LIU Qi-zhong

J4. 2009, 36(2):  285-288. 

Abstract ( 1898 )   PDF (525KB) ( 1063 )   Save

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When the electromagnetic scattering property of the body of revolution object is to be analyzed, the mode decomposition technique is usually adopted to alleviate the computational burden. The surface equivalent electric and magnetic currents calculated by this approach are made up of many mode components, so too much computing time will be spent if the far-field is calculated directly by integral operation due to the oscillation of the integrand. Based on the reciprocity theorem, this paper presents a fast calculation method of the far-field scattering from the rotationally symmetric object. By taking advantage of the exponential distribution property of the surface equivalent currents under each mode and the structural property, we deduce the analytical expressions for the integral with respect to the azimuthal angle, and thus the two-dimensional integral is reduced to the easily computed one-dimensional arc-length integral. Simulation results for a dielectric sphere irradiated by the plane wave indicate that it will take 212 seconds to calculate the far-field scattering if the 30-point Gaussian integration is used, while only less than 1 second is needed by our presented method under the same discreteness and computer hardware.


Analyses of millimeter-wave reflector antennas using a novel fast method


SU Dao-yi1;FU De-min1;YANG Hua2

J4. 2009, 36(2):  289-293. 

Abstract ( 2056 )   PDF (628KB) ( 1038 )   Save

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A novel approach to computing millimeter-wave reflectors is proposed. In this approach, the computational model is created by means of the axisymmetry property and the MoM based on the bodies of revolution is used to analyze this model. To reduce the number of unknown quantities, the hybrid base functions are used, i.e., the entire-domain base functions are applied in the main reflector with a flat geometry, and sub-domain base functions in the complex feed source region. Computational results are compared with those obtained by the full-wave MOM and experiment. It is shown that the numerical results are in good agreement with the results obtained by the full-wave MOM and the measured data, and supports a new way to design high-performance microwave transmission antennas.


New modeling method for the microwave nonlinear circuit


SUN Lu;WANG Jia-li

J4. 2009, 36(2):  294-297. 

Abstract ( 1759 )   PDF (563KB) ( 961 )   Save

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The linear scattering parameter can not represent and design the nonlinear microwave circuit accurately. The definition of nonlinear scattering function can be introduced similar to the linear network parameter. The theoretical system of the nonlinear scattering function has been built based on the conclusions of their linearization, definition and characteristic. The nonlinear network measurement system based on the digital oscilloscope is built. To the microwave transistor, amplitude and phase of incident and reflected waves can be obtained. The nonlinear scattering function can be extracted from the measuremental result, and the experimental results conform to the rule for the nonlinear microwave circuit. This theory can be used as a new tool to character the nonlinear microwave circuit.


Growth and characterization of polycrystal SiC films on porous Si substrates via APCVD process


JIA Hu-jun;YANG Yin-tang;LI Yue-jin

J4. 2009, 36(2):  298-300. 

Abstract ( 1825 )   PDF (1631KB) ( 954 )   Save

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Using a SiH₄-C₃H₈-H₂ reaction gas system,polycrystal 3C-SiC films have been grown on Si(100) substrates with different porous silicon buffers via atmospheric pressure chemical vapor deposition (APCVD) process.The effect of the porosity of porous Si on the grown films quality is studied. Experimental results show that a polysilcon film with SiC(111) grains can be obtained when the porosity of porous silicon is relatively low.With the porosity increasing,the grown films change from porous SiC to poly SiC films with a preferential orientation growth along the <111> direction.


Extreme value analysis of RLC interconnect delay induced by process variations


LI Jian-wei;DONG Gang;YANG Yin-tang;WANG Zeng

J4. 2009, 36(2):  301-307. 

Abstract ( 1590 )   PDF (722KB) ( 1016 )   Save

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Based on the process corners analysis and equivalent Elmore delay model, a fast extreme value estimation of RLC interconnect delay induced by process variations is presented. It can be used to compute the best-case and worst-case RLC interconnect delay caused by process variations. Simulations for 68nm, 45nm, 36nm and 25nm technologies are given. Results show that the new method has the characteristics of a fast calculating speed and high accuracy, and that the proposed method is less than 7％ in error compared with the HSPICE. It can be used to analyze the delay limit of the critical path in STA.


Design of a high efficiency and filterless stereo class-D audio power amplifier


LIU Lian-xi;YANG Yin-tang;ZHU Zhang-ming

J4. 2009, 36(2):  308-313. 

Abstract ( 1838 )   PDF (917KB) ( 1360 )   Save

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This paper presents a high efficiency stereo single-chip class-D power amplifier based on the CSMC 0.5μm DPDM CMOS process. Using a differential negative feedback scheme and a H-bridge output stage, it eliminates the output lowpass LC filter. Simulation results and measurements both show that when the THD+N is less than 0.5％, the power amplifier can deliver more than 3.5W×2 into 3Ω loads without a filter at the power supply voltage of 5V. The maximal efficiency of the amplifier is up to 90％ from 3V to 6V of the power supply voltage. It achieves the THD+N of each channel of less than 0.1％, when the delivered power is less than 3.0W and the supply voltage is 5V.


Study of the incremental crosstalk stimulation testing model of high-speed interconnects


SHANG Yu-ling1;2;LI Yu-shan1

J4. 2009, 36(2):  314-321. 

Abstract ( 1625 )   PDF (710KB) ( 880 )   Save

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Crosstalk stimulation testing is a very important issue for high-speed interconnects’ signal integrity. Formal description of high-speed interconnects’ geometry structure is built. The principle of primary and secondary factors, the principle of effective aggression, and the principle of symmetry are presented. Primary and secondary factors of crosstalk are analyzed based on orthogonal design. An incremental crosstalk stimulation test model is studied according to analytical results. This model takes interconnects’ geometry characteristics into account. Fault diagnosis is implemented as soon as test patterns are generated and applied, so both the test set and test time are decreased greatly. Finally, simulation experiments are implemented and results show that the compact index of this model is better than those of the multiple transition model and half-transition model. This model is more effective because it spends less time testing more types of crosstalk faults for the non-ideal interconnect system.


Investigation electromagnetic scattering from the 1-D band-limited Weierstrass fractal rough surface of the layered medium


REN Xin-cheng1;2;GUO Li-xin1

J4. 2009, 36(2):  322-330. 

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The electromagnetic scattering from the rough surface of the layered medium with plane wave incidence is investigated. The formula for the scattering coefficient for different polarizations is derived using the small perturbation method. A 1-D band-limited Weierstrass fractal rough surface is presented for describing the natural rough surface of the layered medium, and the formula of the scattering coefficient is derived in association with the power spectrum density of the 1-D band-limited Weierstrass rough surface. The angular distribution of the scattering coefficient of the HH polarization is obtained by numerical implementation, the influence of the fractal dimension, the special fundamental frequency, the scale interval, the permittivity of substrate medium, the permittivity and the mean layer thickness of intermediate medium, the root mean square of rough surface, and the frequency of the incident wave on the bistaticscattering coefficient is discussed. The fractal characteristics, the basic characteristics, the zonal characteristics and the characteristics with a varying frequency of the scattering coefficient from the 1-D band-limited Weierstrass fractal rough surface are obtained.


Research on variations of least square support vector machine


DU Zhe;LIU San-yang

J4. 2009, 36(2):  331-337. 

Abstract ( 1941 )   PDF (675KB) ( 1220 )   Save

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The geometric meaning of the Least Square Support Vector Machine(LSSVM) for classification is presented. Then the Proximal Support Vector Machine(PSVM) is extended equivalently to the regression problem, and a new nonlinear model of PSVM, the so-called Direct Support Vector Machine(DSVM), is proposed. Compared with LSSVM, both PSVM and DSVM enforce the convexity of the problem and the computing complexity is small. But in the nonlinear case, DSVM is simpler than PSVM and the nonlinear model coincides with the linear, by substituting the kernel function. Numerical experiments show that, the linear PSVM is at least twice faster than the LSSVM, and that the nonlinear DSVM is about twice faster than the PSVM in terms of the training speed. The linear LSSVM and PSVM almost have the equal generalized abilities, but the DSVM has a higher one than the nonlinear PSVM.


Model checking interval temporal logic


ZHANG Hai-bin;DUAN Zhen-hua

J4. 2009, 36(2):  338-342. 

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To check whether a system represented by a labelled finite state automaton meets a property described by an interval temporal logic formula, a set of rules are defined. Using such rules, a chop-automaton which accepts all intervals satisfying this interval temporal logic formula can be constructed. In addition, a rule for translating a chop-automaton to a labelled finite state automaton is also defined. Thus, the model checking problem for the interval temporal logic can be solved by testing language inclusion between two labelled finite state automata.


Structure and kinematic analysis of radially deployable planar linkages


AN Ming-ming;LI Tuan-jie;LI Tao

J4. 2009, 36(2):  343-346. 

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Based on the structural geometrical connections of a radially foldable planar linkage, the locus of the hinged points in a scissor-like unit composed of angulated elements is derived, the structural constrained conditions of the scissor-like unit are discussed when the hinged points move radially. Then we present the kinematic equations of two inter-connected angulated elements and establish the kinematic model of deployment for foldable linkages using the method of coordinate transformation. Some new properties of this radially foldable linkages are revealed, including the condition for the maximum deployed extension and the angulated relationship between two inter-connected elements. And we have established the structure connections and kinematic model of multilayer deployable linkages by discussing the special case of all the hinged points in the deployable linkage moving radially. Finally, simulation examples verify the effectiveness of the kinematics analysis method.


Analysis of the coupled problems between structure and electromagnetism based on discrete meshes


SONG Li-wei;ZHENG Fei

J4. 2009, 36(2):  347-352. 

Abstract ( 1958 )   PDF (1370KB) ( 1062 )   Save

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To analyze the interaction between mechanical structure and electromagnetism, the concept of coupled problems and its mechanical-electromagnetic coupling model are presented. This model can be simulated based on the same discrete meshes. Because the required mesh sizes of the geometry are allowed due to the precision of electromagnetic analysis, the number of meshes is increased by the iterative method to decrease the increscent mesh sizes in the process of structural analysis. Then the effect of the structural distortion on electromagnetism can be obtained by the method of moment. Finally, the given model is applied in an electromagnetic scatting and an antenna’s radiation. The obtained results prove that the effect of the structural distortion on electromagnetism is not negligible. This study can be used for the design of structure and electromagnetism.


Robust H_∞ control for a class of uncertain discrete fuzzy system with time-delay


ZHANG Guo;LI Jun-min

J4. 2009, 36(2):  353-358. 

Abstract ( 1689 )   PDF (530KB) ( 934 )   Save

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The robust H_∞ stability control problem is considered for a class of discrete uncertain fuzzy system with time-delay. Based on the fuzzy Lyapunov-Krasovskii function (LFK), a fuzzy controller is designed to acquire globally asymptotical stability for the discrete uncertain fuzzy time-delay system with the method of parallel distributed compensation (PDC). Then a new sufficient condition for checking the stability of the closed-loop fuzzy system is proposed and proved. The controller design involves solving a set of linear matrix inequalities (LMIs) by introducing multiply additional matrix variables. Due to the idea of fuzzy LKF, the obtained robust stability condition has less conservativeness than the one based on the common LKF. A simulation example shows that the approach is effective.


Novel two-channel time-interleaved high-order ΣΔ modulator


YANG Xiao;CHEN Gui-can;CHENG Jun;ZHANG Hong

J4. 2009, 36(2):  359-365. 

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To alleviate the folded noise caused by coefficient mismatches between the two channels of two-channel time-interleaved (TI) ΣΔ modulators and simplify the circuit of the modulators, a novel two-channel time-interleaved high-order ΣΔ modulator is proposed. Adding a zero at the frequency of F_s/2 to a conventional noise transfers function (NTF), the amplitude of the NTF at the high frequency can be reduced, and then the amount of the folded noise is reduced. Based on the theory of block digital filters and the method of timing equivalence, the implemented circuit for the proposed modulator is derived from the prototype of a conventional single-channel single-loop forth-order 4-bit distributed feedforward ΣΔ modulator, in which the opamps can be shared by tow channels of the first three stages, resulting in simplification in hardware complexity. A system model containing coefficient mismatches is built and simulated. Simulation results show that the proposed two-channel TI high-order ΣΔ modulator can alleviate the folded noise and improve the performance.


Novel hierarchical framework for the network management system based on multi-Agent collaboration


JIANG Fei1;2;SHI Hao-shan1;XU Zhi-yan3;DONG Xiang-jun1

J4. 2009, 36(2):  366-372. 

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For the purpose of solving the defects of the traditional mobile-agent-based SNMP network management system, such as low system efficiency,long system response time, poor collaborative performance and poor extendibility of agent, a novel hierarchical framework for the network management system based on multi-agent collaboration is designed. This framework contains four levels: the top level for the manager station, the multi-mobile-agent collaboration level, the multi-SNMP-agent collaboration level and the network element level. For the second level, a strategy model which consists of two parts: the middle-tier strategy based on the mobile agent and the multi-mobile-agent collaboration strategy is proposed, which applys the SNMP agent for the stationary agent, implements the collection of the managed datas parallelly and intelligently by using a certain number of mobile agents. A collaboration mechanism among master-agent and sub-agent based on the SNMP protocol for the third level is also realized, which aims at improving the limitations of the AgentX protocol.This mechanism establishes an SNMP agent task model, divides the SNMP agent into the master-agent and sub-agent and makes them adopt the SNMP protocol to collaborate together. Simulation demonstrates that the framework can decrease the bandwidth occupation about 26.9％ compared with the traditional SNMP network management model based on the mobile agent and AgentX protocol, and that the response time is decreased by 29.5％. It is more appropriate for the framework to be applied in large and complicated distributed network environment.


Novel approach to test compaction based on limited scan operation


LIU Yu-kun1;SUN Chao2;ZHANG Li-yong1

J4. 2009, 36(2):  373-377. 

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According to the problem of the significant increasing testing cost of VLSI caused by the significant increase in testing time, this paper proposes a novel approach to test compaction for scan circuits that use limited scan operations instead of full scan operations between test pairs. This leads to very aggressive compaction on the test application time cost under the same fault coverage. The experimental result of benchmark circuits shows that the test application time cost of the proposed method is about 50％ that of the conventional methods.


Proactive recovery algorithm in the distributed intrusion-tolerance system


ZHOU Hua;MENG Xiang-ru;ZHANG Li;QIAO Xiang-dong

J4. 2009, 36(2):  378-384. 

Abstract ( 1971 )   PDF (777KB) ( 1019 )   Save

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According to the fact that the intrusions can corrupt the safety of system resources, the concept of resource-safe is proposed and a proactive recovery algorithm is implemented in the component of the trusted timely computing base. In order to achieve the intrusion tolerance, the algorithm recovers every node in the system periodically to eliminate the influence of intrusions. The simulation experiment shows that the system unavailability is closely relative to system parameters, and that its results could be useful references to configure and evaluate the intrusion tolerance system.