Table of Content

20 December 2009 Volume 36 Issue 6

  

Original Articles

New precise space ranging algorithm for multi-carrier systems

REN Guang-liang;BAI Yun;NI Hao;SUN Chui-qiang

J4. 2009, 36(6):  957-961. 

Abstract ( 1850 )   PDF (580KB) ( 1735 )   Save

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According to the requirement of the precise space ranging, the Cramer-Rao Lower Bound (CRLB) is derived for the maximum-likelihood (ML) transmission delay estimation algorithm in multi-carrier systems from its expression. Based on the form of the likelihood function, a new iterative algorithm for delay estimation is proposed. Simulation results show that the proposed method leads to a high convergence rate. Compared with the exhaustive searching method, its complexity is low. The ranging accuracy of the proposed method is at least 3 times that of the phase measurement based multi-carrier method at the  -10dB signal-to-noise ratio (SNR). With the increase of the SNR, the root-of-mean-square-errors (RMSEs) of the proposed method approach the Cramer-Rao lower bound.

Research on the synchronization scheme of  a cognitive asynchronous frequency-hopping communication system

HE Xian-deng;PEI Chang-xing;ZHANG Zheng-hao;CHEN Nan

J4. 2009, 36(6):  962-967. 

Abstract ( 1901 )   PDF (938KB) ( 1596 )   Save

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A synchronization scheme for a cognitive asynchronous frequency-hopping communication system(CAFHCS) is proposed. There are two optional frequency-hopping patterns in this scheme. In transmiting information in the current hop, the status of the two frequency points which are calculated by the two patterns for the next hop are sensed simultaneously. The transmitter selects the frequency point for the next hop adaptively according to the sensing results, which improves the anti-jamming performance of the asynchronous frequency-hopping communication system(AFHCS). It is observed from simulation results that the users' capacity of the CAFHCS increases over 6 times compared with that of the AFHCS when the probability of synchronization is above 95％. By introducing the cyclic prefix to a hop signal, the frequency-hopping pattern recognition is implemented adaptively at the receiver, and the difficult problem of bit synchronization of the frequency-hopping signal is solved as well. Furthermore, the performance analysis of the synchronization scheme for AFHCS and CAFHCS are given.

Improved IMBE algorithm with adaptive forward-backward quantization

LI Ye;YANG Jia-wei;LIANG Yan-xia

J4. 2009, 36(6):  968-971+984. 

Abstract ( 1522 )   PDF (611KB) ( 1218 )   Save

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A new method for updating the codebook is proposed to improve the accuracy of the adaptive backward codebook. This new algorithm sets up a line spectrum frequency coefficient's adaptive backward codebook, which implements the interpolation between the line spectrum frequency coefficients to improve the precision of the linear prediction coefficient's adaptive backward codebook. As a result, it increases the use frequency of the backward quantization and reduces the average coding rate. Objective and subjective tests show that the quality of speech synthesized by the improved method is superior to the one synthesized by the IMBE algorithm with adaptive forward-backward quantization, and as good as the one synthesized by the  2.4kbps IMBE algorithm.

Imaging study of spotlight SAR using FMCW

LIANG Yi;GAO Zhao-zhao;XING Meng-dao;BAO Zheng

J4. 2009, 36(6):  972-978. 

Abstract ( 1408 )   PDF (1150KB) ( 1271 )   Save

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Based on the difference in working mode between Frequency Modulated Continuous Wave (FMCW) Synthetic Aperture Radar (SAR) and Pulse Synthetic Aperture Radar, which leads to a different form of the echo, this paper establishes the model of the Spotlight FMCW SAR receiving signal, analyzes its characteristics, and reveals the effect of Doppler frequency shift induced by the continuous motion in range direction while radar is transmitting and receiving signals, which affects azimuth focusing ultimately. For the problem of azimuth spectral folding, this paper adopts azimuth pre-filtering processing, which increases the sampling frequency through interpolation. Since azimuth pre-filtering can realize bulk azimuth data compression, the number of azimuth points does not increase significantly. Finally, based on the Frequency Scaling Algorithm, residual data focusing can be achieved. Point targets simulation verifies the analysis and validity of the algorithm. In addition, for the Doppler frequency shift induced by the continuous motion while radar is transmitting and receiving signals, we also analyze its effect on imaging and give the corresponding compensation method.

Analysis of the dependence of the vertical baseline bistatic airborne radar clutter spectrum on range

LI Ming;LIAO Gui-sheng;YUAN Xiao-yi;WEN Jun

J4. 2009, 36(6):  979-984. 

Abstract ( 1679 )   PDF (1684KB) ( 1230 )   Save

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In actual environments, the vertical height between airborne transmitter and airborne receiver is always different, and as a result, a vertical baseline appears between the two airplanes. This paper first analyses the common frame of bistatic airborne radar, and then takes bistatic airborne radar as a special example, which shows the influence of the clutter Doppler frequency from the different height between the two airplanes. The paper carries out computer simulation on four key models of bistatic airborne radar, and then explains the influence of the vertical baseline based on the clutter spectrum analysis. It is discovered that bistatic airborne radar with a proper vertical baseline will decrease the dependence of the clutter spectrum on range and improve the ground moving target indication performance.

SVD based robust approach for blind source separation

ZHANG Wei-tao;LOU Shun-tian;ZHANG Yan-liang

J4. 2009, 36(6):  985-989. 

Abstract ( 1663 )   PDF (556KB) ( 1274 )   Save

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From the point of view of the estimating function proposed by Amari, we investigate the intrinsic characteristics of the optimal separating matrix for blind source separation (BSS) in the sense of minimizing nonlinear principal component analysis criterion, which formulates the optimal solution as the normalized cross correlation between the input and nonlinearized output. We thus present a singular value decomposition (SVD) based robust scheme for BSS, which considers the estimating procedure of the separating matrix as a nonlinear power iteration problem. By performing SVD of the power term, the computational load can be significantly reduced, which results from circumventing the difficulty of solving the inverse square root of the normalization term. Since the separating matrix is properly normalized by the positive definite inverse square root of the power term, the robustness of this algorithm is greatly improved. Moreover, this guarantees the orthonormality of the separating matrix at each iteration. Some simulation results are also provided to demonstrate the performance of the proposed algorithm.

Research on architecture and key technologies of the grid communication network

FAN Shu-yan;XIONG Gao-yun

J4. 2009, 36(6):  990-995. 

Abstract ( 1649 )   PDF (1307KB) ( 1484 )   Save

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How to improve the ability of a manageable and controllable communication network in supporting information grid application is studied. A service-oriented architecture of the GCN (Grid Communication Network) is presented and the key technologies of the GCN are studied. The core idea of the architecture is to increase the direct interaction between grid application and network, to provide the ability of automatic transport according to the transmission demands of grid application information, to guarantee end-to-end QoS and improve network resource utility at the same time by adding GNS (Grid Network Service) to the current communication networks. Some services of the GNS for the ATM/MPLS communication network are developped based on the policy mechanism. A GCN prototype system is constructed by integrating the GNS and the ATM/MPLS network. Demonstration results show that the architecture of the GCN proposed in this paper and the key technologies are feasible.

Dynamic spectrum allocation based on continuous double auctions in cognitive radio networks

LIU Ying-ting;CAI Jue-ping;LI Zan;ZHANG Hai-lin;LIU Quan-yang

J4. 2009, 36(6):  996-1002. 

Abstract ( 2473 )   PDF (696KB) ( 1414 )   Save

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Multiple primary and multiple secondary users coexist in non-cooperation cognitive networks. All primary and secondary users are selfish and rational with the hope of acquiring the maximum gain on condition that they do not harm the profits of others, which accords with the hypothesis of users in continuous double auctions. For this characteristic, dynamic spectrum allocation based on fuzzy-logic continuous double auctions is proposed, based on the theory of experimental economics. In spectrum auctions, every user uses bidding strategy based on the fuzzy-logic. With this method, they can adjust their bidding steps in time according to the business situation, and reduce the time of bid to finish the business rapidly. Simulation results show that our proposed scheme has 85％ efficiency of spectrum usage. Dynamic Spectrum allocation in the multi-to-multi situation in non-cooperation cognitive networks is solved effectively with the method proposed in the paper.

Research on narrowband radar detection for thehigh-speed multi-target

SU Jun-hai;LI Ya-chao;XING Meng-dao

J4. 2009, 36(6):  1003-1009. 

Abstract ( 1540 )   PDF (1613KB) ( 1297 )   Save

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A serious range walk will result from the high speed of a target; and the low pulse repetition frequency will also result in cross-range undersampling, so the conventional Keystone transform will not be valid, these are disadvantageous for effective target energy accumulation. And it is also disadvantageous for multi-target detection due to their different range walk ratios. A method for narrowband radar detection for a high speed multi-target based on the clean technique is presented in case of the problems above. First, a Keystone transform will be applied to range compressed data and then we compensate the range walk function for which the target has the maximal energy. After that the quadratic phase term is searched for and subsequently compensated. Then a cross-range FFT is performed for detection, and finally the strongest target is filtered and the next potential target detected. Simulation results show that the proposed method is effective and applicable.

High accuracy complex sinusoid frequency estimator in low SNR environment

LI Xiao-jie;XU Lu-ping;ZHOU Xue-song

J4. 2009, 36(6):  1010-1014+1020. 

Abstract ( 1916 )   PDF (662KB) ( 1589 )   Save

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By using the information on both amplitude and phase, the frequency estimation algorithm MAP/ML can achieve high accuracy frequency estimation when the SNR is high. But the performance will be greatly degraded at a low SNR. Based on analyzing the reason, a new maximum likelihood (ML) estimation method is presented, which can confirm the coherent integration length and the unwound sequence combined with FFT. Using the coarse frequency estimation value for frequency shift, signal's frequency and the variation of sequence's phase are limited to a certain sphere, so that the Cramer-Rao lower bound(CRLB) limits with various coherent integration lengths are derived, and the optimal coherent integration length of data subsection is determined, which contributes to attaining the optimal balance between the estimation accuracy and the SNR gain. In addition, an estimation sequence selecting method based on the phase variance of the phase-shifted sequence is proposed, which avoids the phase unwraping process. Finally, the Monte Carlo simulation result shows that the performance of the estimator can approach the CRLB very closely.

Recursive total least l_p-norm algorithm for adaptive IIR filtering in α stable noise environments

ZHANG Bin;FENG Da-zheng;LIU Jian-qiang

J4. 2009, 36(6):  1015-1020. 

Abstract ( 1780 )   PDF (639KB) ( 1194 )   Save

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When both the input and the output of a linear system are corrupted by α stable noises, the classical least mean l_p-norm (LMP) algorithms usually provide a biased solution and the total least mean l_p-norm (TLMP) algorithms suffer from slow convergence. The aim of this paper is to develop a recursive total least l_p-norm (IIR_RTLP) algorithm for adaptive IIR filtering with noisy data. The proposed IIR_RTLP algorithm makes the expectation of l_p-norm of the error be minimized when both the input and the output are corrupted by α stable noises. In ordor to trace the time-varing system and increase the speed of convergence, the IIR_RTLP algorithm recursively updates the adaptive filter coefficients on the basis of the matrix inversion lemma and the power iteration. Simulation results show that the IIR_RTLP algorithm can lead to faster convergence and a smaller system error than the existing TLMP algorithms for adaptive IIR filtering.

Transmit beampattern matching design and waveform optimization for MIMO radar

HU Liang-bing;LIU Hong-wei;LIU Bao-chang;WU Shun-jun

J4. 2009, 36(6):  1021-1026+1033. 

Abstract ( 2519 )   PDF (945KB) ( 1347 )   Save

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A covariance matrix of transmit signal waveforms is optimized via semi-definite programming (SDP) for matching the desired transmit beampattern of an MIMO radar system. Based on the covariance matrix above and using the cyclic algorithm (CA) and the min-max method proposed, low space-time sidelobes are achieved by optimizing waveform phases of the transmit signal waveforms with constant modulus. Additionally, a convex programming method is proposed to design the space-time mismatched filters, and then the space-time sidelobes are furthermore reduced.

Optimal design method combined aribtary phase codes with pulse compression filters optimization

HE Xue-hui;WU Zhao-ping;SU Tao;WU Shun-jun

J4. 2009, 36(6):  1027-1033. 

Abstract ( 1692 )   PDF (722KB) ( 1380 )   Save

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For the polyphase codes with arbitray phase, an optimal design method combined with pulse compression filters is proposed. Under the constraint of the maximum gain loss, The minimum peak sidelobe suppression correlator for existing phase codes is given by convex optimization, on the basis of which, a novel phase code is presented. Its range sidelobe can be farther decreased by multi-iterative operations. Without increasing the length of pulse compression filters, a nearly optimal peak sidelobe level is achieved by the presented method at the cost of less loss in process gain. The presented algorithm has many advantages, such as flexible design and quick convergence. The validity of the presented method is demonstrated by simulation results.

Design of a novel ultra-wideband tapered slot antenna

SONG Yue;JIAO Yong-chang;ZHANG Fu-shun;WANG Nai-biao

J4. 2009, 36(6):  1034-1038. 

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A microstrip fed ultra-wideband tapered slot antenna is designed and fabricated. The wideband impedance matching is obtained by the use of a modified microstrip/slotline transition. The improvement of impedance characteristics at the lower band is achieved by introducing a novel flare curve as a radiation part. The measured results of the proposed antenna demonstrate that this directional antenna achieves a ratio bandwidth of  15.4∶1 for VSWR≤2 from 0.92 to  14.25GHz. The front-to-back ratio and cross polarization ratio of its radiation patterns over the operating band are greater then 18 dB and less than  -18dB, respectively.

X-band single stage GaN solid-state power amplifier

CHEN Chi;HAO Yue;FENG Hui;MA Xiao-hua;ZHANG Jin-cheng;HU Shi-gang

J4. 2009, 36(6):  1039-1043. 

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Based on the self-developed AlGaN/GaN HEMT with 2.5-mm gate width technology on the SiC substrate, the X-band GaN solid-state power amplifier module is fabricated. The module consists of the AlGaN/GaN HEMT, DC-bias circuit and microstrip line. The chamber structure made of metal and the test fixture are designed for grounding and thermal transmission under the CW operating condition. Two section bias circuits for the AlGaN/GaN HEMT are presented. The special R-C networks and gate resistance are used for cancellation of self-oscillation at both the low frequency and radio frequency. The microstrip stubs are used for input matching and output matching. Under the  V_ds= 27V,  V_gs= -4.0V CW operating condition at  8GHz, the amplifier module exhibits a line gain of  5.6dB with a power-added efficiency of 30.5％, the output power of  40.25dBm (10.5W), and the power gain compression of  2dB. Between  8GHz and  8.5GHz, the variation of output power is  1dB.

Study of optimum fitting using the genetic algorithm for multipath mitigation in GPS receivers

WANG Jiang-an;ZHUANG Yi-qi;LI Di;JIN Zhao

J4. 2009, 36(6):  1044-1048. 

Abstract ( 2018 )   PDF (616KB) ( 1164 )   Save

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Traditional GPS receivers can not mitigate the close-in multipath effectively, which reduces the positioning accuracy. A method based on the Genetic Algorithm to approximate the GPS close-in multipath is proposed, which transforms multipath estimation to a best fitting problem. The Genetic Algorithm is used in order to avoid the model's falling into the local least value. By accurate estimation of multipath parameters, the multipath is mitigated effectively. The step of the algorithm is described, and the simulation proves that the precision of the measured pseudorange is improved by 2 times in the close-in multipath condition.

Study of (112-0) non polar a-plane GaN on the (11-02) r-plane sapphire

XU Sheng-rui;DUAN Huan-tao;HAO Yue;ZHANG Jin-cheng;ZHANG Jin-feng;NI Jin-yu;HU S

J4. 2009, 36(6):  1049-1052+1058. 

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The spontaneous and piezoelectric polarizatio represent one of the unsolved problems in utilizing GaN for fabricating light-emitting devices. To solve the problem, non-polar GaN structures have been studied. Low-temperature AlN buffers are used for (112-0) a-plane GaN growth on the (11-02) r-plane sapphire. A combination of atomic force microscopy (AFM), high resolution X-ray diffraction (XRD) and photoluminescence (PL) spectrum is used to characterize dislocation of the (112-0) a-plane and (0001) c-plane GaN epilayer. Compared with the typical hexagonal dislocation of c-plane GaN, this shows great difference with the conventional polar GaN, and the pit of the a-plane GaN epilayer is triangle, with the possible formation mechanisms of these faults discussed and the triangular pit directions also investigated.

Full chip temperature optimization for considering thermal-electric coupling effects

LENG Peng;DONG Gang;CHAI Chang-chun;YANG Yin-tang

J4. 2009, 36(6):  1053-1058. 

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Based on the fact that convergent results reflecting the feedback between power and temperature can be found by using the available power model and HotSpot software, a method is proposed for full chip temperature optimization. In the model, thermal-electric coupling effects among delay, power and temperature are taken into consideration. Simulations for the AMD Athlon 64 processor in 90-nm technology are given. Results show that the optimized chip temperature characteristics with lower temperature, decreased power and temperature gradients can be achieved.

Quantitative analysis of noise's linearity and Gaussianity in electronic devices

LI Wei-hua;ZHUANG Yi-qi;DU Lei;BAO Jun-lin;MA Zhong-fa

J4. 2009, 36(6):  1059-1062+1091. 

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A quantitative analysis method of noise's linearity and Gaussianity in electronic devices is deduced on the basis of the higher order statistics (HOS) theory, from which a parameter named the quadratic sum of the bicoherence is brought forward. Through the analysis of four types of noise signals, non-linear non-Gaussian noise, linear non-Gaussian noise, non-linear Gaussian noise, and linear Gaussian noise, a quantitative criterion for appraising the linearity and the Gaussianity of noise signals is presented. By applying this method to the analysis of real noise signals in electronic devices, it is proved that real noise signals could be clearly classified into the above-mentioned four types of noise. This work provides a theoretical basis and quantitative criterion for the analysis of noise's nonconventional characteristic in electronic devices.

Star-cluster double-loop topology for the network-on-chip

LIU You-yao;HAN Jun-gang

J4. 2009, 36(6):  1063-1069. 

Abstract ( 1823 )   PDF (906KB) ( 1420 )   Save

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With the feature size of semiconductor process reduced and IP(Intellectual Properties)  cores increased, interconnection network architectures on the chip have a great influence on the performance and area of System-on-Chip(SoC) design. Focusing on decreasing node degrees, reducing links and reusing the router node, a regular Network-on-Chip(NoC) architecture, named the Star-Cluster Double-Loop(SCDL(2m)) interconnection network, is proposed. The topology of SCDL(2m) is simple, planar, symmetric and scalable in architecture, and it has 4m nodes. Each node connects three adjacent nodes and four IP cores. The nodes of SCDL(2m) adopt the Johnson coding scheme that can make the design of routing algorithm simple and efficient. The SCDL(2m) is compared with Cluster-Ring and Cluster-Mesh by simulation and analysis, both under a uniform load and under more realistic load assumptions in several network size scenarios. The results show that the SCDL(2m) topology is a good trade-off between performance and cost. It is a better topology for NoC.

Approach for adaptive infrared thermal image enhancement

KOU Xiao-ming;LIU Shang-qian;HONG Ming;WANG Da-bao

J4. 2009, 36(6):  1070-1074. 

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As for the inadequate contrast of infrared thermal imaging, as S curve mapping function is proposed to enhance target objectives and in the meantime suppress background clutters, which has the same range of domain with a variable interval and a non-symmetrical inflection point. With the need of adaptive enhancement for the changing scene, a dynamic self-adaptive model is proposed to adjust the parameters of the S curve based on the scene. By using the threshold and modulation of histogram as the input parameters and the parameters of the enhancement algorithm as the outputs, the coefficients of the model is determined based on typical samples of data through the artificial neural network BP algorithm, with the application showing that this approach is effective.

Dim infrared targets detection based on background prediction

LI Fan;LIU Shang-qian;HONG Ming;QIN Han-lin

J4. 2009, 36(6):  1075-1078. 

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In order to solve the difficult problem of dim targets detection in complicated background, a new bilateral filtering method for background prediction is presented. In this method, the true image background is estimated adaptively via bilateral filtering, and the estimated image is subtracted from the source image to suppress background details and enhance target information. To improve the performance of dim targets detection, the gradient statistics is introduced to decrease the compatational amount. Simulations and experiments show that the new algorithm is more efficient in detecting the dim target from complicated background compared with the method based on bilateral filtering.

Topology optimization of the multi-random parameters continuum structure under the strain energy constraint

SONG Zong-feng;CHEN Jian-jun;ZHU Zeng-qing

J4. 2009, 36(6):  1079-1085. 

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The topology optimization design problem for the planar continuum structure with the randomness of both the geometry and physical parameters under the structural total strain energy constraint is studied. A mathematical model for topology optimization design with a random structure is established, in which the minimum mean of structural weight is taken as the objective function, the structural shape topology information is taken as design variables, and the probabilistic reliability index of structural total strain energy is taken as the constraint condition. The computational expressions for the mean value and mean variance of the structural strain energy response are presented by the algebra method. The solution strategy of the bi-directional evolutionary structural optimization method is used in the optimization. Through two examples, the rationality and feasibility of the optimization model and solution strategy are validated.

Efficient video indexing method using dynamic distance measure for the principal component

CUI Jiang-tao;GUO Yong;LI Guang-xin

J4. 2009, 36(6):  1086-1091. 

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The Bounded Coordinate System (BCS) approach is a novel video representation model, which can summarize a video to a coordinate system determined by Principal Component Analysis (PCA). The similarity measure of BCS considers the operations of rotation and scaling for coordinate system matching. However, the BCS approach can not always obtain the minimum distance of rotation and scaling between two bounded Principal Components. To overcome the handicap of the original BCS approach, an improving approach applying dynamic distance measure for rotation and scaling distance is presented in this paper. The new approach can calculate the minimum rotation and scaling distance between two bounded Principal Components, and improve the query precision. Our extensive performance study on a large database of more than  30000 video clips demonstrates that the new approach achieves a higher search accuracy than the BCS approach.

Image restoration model and algorithms with second-generation curvelets

J4. 2009, 36(6):  1092-1096. 

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Suppose that an image belongs to Besov spaces, one can measure sparse decompositions on wavelet basis by the fact that the Besov norms have equivalent descriptions by means of wavelet coefficients. But as is well known, wavelets fail to very efficiently represent smooth objects with edges while curvelets provide an optimally sparse representation of objects with singularities along C2 edges. Based on the analysis above, a novel model using second-generation curvelets is proposed for restoration of the image. Especially, curvelets-type decomposition spaces are employed for characterizing the sparsity of second-generation curvelet coefficients. On the other hand, an iterative hard shrinkage algorithm is obtained by using the generalized conditional gradient method, as well as convergent theorems for solutions and stopping criterion. Finally, experiments show that the proposed algorithm produces better results in terms of both signal-to-noise ratio and subjective visual quality than methods available.

Study the propagation characteristic of radio wave in atmospheric duct

YANG Chao;GUO Li-xin;LI Hong-qiang;WU Zhen-sen

J4. 2009, 36(6):  1097-1102+1138. 

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To investigate the propagation properties of radio waves in atmospheric duct, according to the fact that the traditional Split-step Fourier Transform method does not work well in treating the propagation problem with the impedance boundary condition, the Discrete Mixed Fourier Transform Method is used to solve the narrow angle parabolic equation with the impedance boundary condition is presented, and a detailed computational method and the solving step are also given. In the process of discretization of the auxiliary function, the traditional central difference formula is replaced by the backward difference formula, and numerical results show the method is of good stability. This approach establishes the theoretical foundation for studying the assessment of radar performance and radar detection shadow zone.

Robust channel blind balance approach to strong target signals contamination

ZHOU Zheng-guang;LIAO Gui-sheng;ZHU Sheng-qi

J4. 2009, 36(6):  1103-1107. 

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A robust channel balance approach is proposed for a multi-channel SAR-GMTI system. Firstly, the modulus normalized vector corresponding to the pixel data vector is constructed and its covariance matrix is formed. Secondly, the eigen-decomposition is produced, and the eigenvector associated with the largest eigenvalue contains any information regarding channel imbalance. Lastly, the imbalance is corrected by dividing the element of the pixel data vector by the corresponding element of the selected eigenvector. The effectiveness and robustness of the proposed approach are confirmed by performance analysis and real data processing.

Design and implementation of a novel miniaturized circularly polarized GPS microstrip antenna

SONG Xiao-di;FENG En-xin;FU Jun-mei

J4. 2009, 36(6):  1108-1113. 

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A novel miniaturized circularly polarized microstrip antenna with the EBG structure for GPS applications is designed and constructed. The size of the circularly polarized GPS microstrip antenna desiged by the Koch rectangle fractal is reduced considerably. And the properties of bandwidth and gain are improved effectively due to the introduction of given size EGB designed by the Koch rectangle fractal. Simulation and experimental results show that, compared with the conventional rectangle structure, the proposed antenna has reduced the size by 27％, and increased the axial-ratio bandwidth by about 30％ as well as the gain by 0.2dB due to the application of the EBG structure.

Fast SAR image segmentation method based on the two-dimensional grey entropy model

MA Miao;LU Yan-jing;ZHANG Yan-ning;HE Xue-li

J4. 2009, 36(6):  1114-1119. 

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In order to speed up the segmentation procedure and solve the problem of noise-sensibility in SAR image segmentation, the paper suggests a fast SAR image segmentation method based on the 2D grey entropy model, which integrates the wavelet transform, Genetic Algorithm (GA), image entropy and grey theory. In the method, after an approximation image and a gradient image are deduced from the original image respectively via the wavelet transform, their concurrence matrix is constructed. On the basis of the matrix, a 2D grey entropy based fitness function is designed for GA. And then, after the operations of selection, crossover and mutation, the best threshold is obtained. Finally, our experimental results indicate that the method not only ignores the disturbance of inherent speckle in the SAR image, but also shortens the segmenting time obviously.

Mathematical comprehension of the intersecting cortical model using the lattice theory

GAO Shan;BI Du-yan

J4. 2009, 36(6):  1120-1125. 

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The lattice theory is applied to the comprehension of the pulse parallel propagation characteristic of the intersecting cortical model (ICM) in image processing. In the aspect of the lattice theory, an image is a set of points in higher dimensional space, while the ICM image processing is just to find a mapping relation ordering the points set to a semi-order set. A detailed analysis of applications of ICM to the binary image, gray image and color image processing are conducted, which leads to the validation of the lattice theory foundation for ICM image processing. It provides the mathematical support for the biological-based ICM application.

Fast mode decision algorithm for intra-prediction in H.264 with detection of edge directions

HE Yi-bao;CHEN Zai-xiu;BI Du-yan;MA Xin-zhen;ZHAO Peng

J4. 2009, 36(6):  1126-1131. 

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A tool for intra prediction is introduced in the new video coding standard-H.264, and this technique can cut down the spatial redundancy effectively. Though intra prediction can improve the efficiency of the intra encoder, it is undoubtedly computationally intensive. To overcome this drawback, a novel fast intra prediction algorithm is proposed in this paper. By making use of the division of the macro-block, the edge direction is detected first and the direction of texture is estimated. Then the intra mode decision will be made among several most possible modes, which can diminish the number of the calculation. For variable video sequences, simulation results show that with the proposed algorithm the time of the intra coding can be reduced about 72.64％ while keeping a close quality and precision.

New method for the anti radar missile to antagonize the non-coherent radar decoy

QU Zhi-yu;SI Xi-cai;ZHU Xiao

J4. 2009, 36(6):  1132-1138. 

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The traditional wideband PRS(Passive Radar Seeker) of the ARM (Anti Radar Missile) can not antagonize the radar decoy, a new-style wideband PRS should be developed. Using the super resolution DOA(Direction of Arrival) estimation algorithm to reduce the resolution angle is an effective method for the PRS to antagonize the non-coherent radar decoy. Considering the power and correlation property between radar and non-coherent decoy, an improved subspace DOA estimation method using the invariance property of noise subspace is proposed. Compared to the traditional MUSIC algorithm, this new method shows not only a better resolution in the condition of closely spaced sources, but also superior performance in case of different power or partially correlated sources. The PRS(Passive Radar Seeker) using this new method can distinguish radar and non-coherent decoy with good performance. Both the simulation result and the experimental data confirm the performance of the method.