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    20 June 2009 Volume 36 Issue 3
      
    Original Articles
    Reduced-dimension method for joint-pixel multi-baseline InSAR processing
    SUO Zhi-yong;LI Zhen-fang;WU Jian-xin;BAO Zheng
    J4. 2009, 36(3):  385-417. 
    Abstract ( 1729 )   PDF (1642KB) ( 1426 )   Save
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    For the joint-pixel multi-baseline InSAR processing, the authors achieve the result that when all the SAR images are accurately coregistrated, the dimension of signal-subspace is constant in spite of the number of satellites, then the authors utilize Lanczos iteration to estimate the signal subspace, which avoids eigen-decomposition of high-dimensional covariance matrix, at the same time, they use subspace fitting to replace the projection of the signal subspace onto the noise subspace, the operation complexity is greatly reduced and the precision of the algorithm is also guaranteed. Finally, the validity of the proposed algorithm is proved by the processing results of simulated multi-baseline data and single baseline real data.

    Clutter modeling and analysis for spaceborne bistatic radar
    LIU Nan;ZHANG Lin-rang;YI Yu-sheng;LIU Xin
    J4. 2009, 36(3):  390-437. 
    Abstract ( 2289 )   PDF (978KB) ( 1553 )   Save
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    This paper presents a new clutter model for bistatic spaceborne radar, which takes into account the influences of the elliptic orbits of the satellites, the curving surface of the earth, the earth rotation, the range ambiguity and the geometry of the bistatic radar system on clutter and STAP performance. Based on the model proposed in this paper, an analysis of the characteristic of ground clutter is made. Simulation results show that the space-time distribution of clutter would vary with range and time, which, along with range ambiguity would result in the performance degradation of clutter cancellation. And the GMTI is unachievable if the elements of the receive array are all mounted on one satellite due to its serious Doppler frequency ambiguity and inadequate spatial resolution, which could be resolved by mounting the elements of the receive array sparsely on many distributed small satellites.

    Method for Doppler centroid estimation of airborne radar with a high pulse repetition frequency
    WU Jian-xin;WANG Tong;SUO Zhi-yong
    J4. 2009, 36(3):  396-400. 
    Abstract ( 1643 )   PDF (524KB) ( 1354 )   Save
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    Due to strong coherence between adjacent pulses for a high pulse repetition frequency, a method for estimating the Doppler centroid using multiple pulses is presented. The method constructs the eigenvector corresponding to the largest eigenvalue of the phase covariance matrix, and then the Doppler centroid is estimated based on the eigenvector. The estimation accuarcy of the method is improved about 5 dB compared to that of the correlation function method. Simulation results are given to demonstrate the effectiveness of the method.

    Blind source separation method applicable to dependent sources
    Zhang Yanliang1,LOU Shuntian1,ZHANG Weitao2
    J4. 2009, 36(3):  401-432. 
    Abstract ( 1778 )   PDF (639KB) ( 1428 )   Save
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    The existing methods of blind source separation are mostly based on the precondition of independence of sources. A new blind source separation method is proposed in this paper, which is a two-stage approach and applicable to instantaneous mixtures of dependent sources. Firstly, variances of the ratio between two sensors are compared. Sequent sampling instants, whose variances are equal, are the instants at which only one source exists. The vectors of observation at these instants, are the estimate of the corresponding columns at the mixing matrix. By using this property, the mixing matrix can be estimated correctly. Then, the de-mixing matrix is obtained and sources are recovered. Simulation results illustrate the correctness of the algorithm.

    Fast progressive edge-growth algorithm
    CHEN Lin;FENG Da-zheng
    J4. 2009, 36(3):  406-409. 
    Abstract ( 1467 )   PDF (545KB) ( 1431 )   Save
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    A fast implementation of the Progressive Edge-Growth (PEG) algorithm for constructing low density parity check (LDPC) codes is presented. A balanced search tree is used to sort the check nodes and the variety of the Tanner graph is tracked during the edge growth process. The balanced search tree makes the search for a specified check node have the logarithmic complexity, and the number of times of the tree-expanding of the Tanner graph is significantly reduced by tracing the variety of the Tanner graph. Compared with the indicator-based implementation, the method presented here reduces the complexity effectively. Taking the construction of an LDPC code with length 104 as an example, the time used by the balanced-search-tree based implementation is only about 20 percent of that used by the indicator-based approach.

    New adaptive angular-sector segmentation algorithm for radar ATR based on HRRP
    CHEN Feng;HOU Qing-yu;LIU Hong-wei;BAO Zheng
    J4. 2009, 36(3):  410-417. 
    Abstract ( 2115 )   PDF (1110KB) ( 1544 )   Save
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    In the field of high resolution range profile (HRRP) based radar automatic target recognition (ATR), it is an effective approach to tackle the target-aspect sensitivity by segmenting continuous radar data into several sectors in equal angular intervals. This equal angular-sector segmentation algorithm is based on the condition for good quality of ISAR images, but it is not a satisfactory choice with the application of ATR for its inclination to cause model mismatch, performance limitation, and time-consumption. This paper proposes a recursive algorithm for adaptively angular sector segmenting based on Adaptive Gaussian Classifier (AGC) and Gaussian Processes classifier (GPC).Since the HRRP data are continuous along the azimuth,we first exploit the nonlinear structure characteristic embedded in HRRP data through AGC or GPC, then present a criterion for determining the angular-sector boundary, and finally recursively segment the data. Promising experimental results are presented for measured radar data.

    Simplified receiver for continuous phase QPSK modulation
    LIN Yong-zhao1,2;WU Cheng-ke1;WANG Bu-hong2;CHEN Na1
    J4. 2009, 36(3):  418-423. 
    Abstract ( 2003 )   PDF (587KB) ( 1458 )   Save
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    The complexity of the conventional optimum receiver for continuous phase QPSK (CPQPSK) increases exponentially with the length of the shaped frequency pulse. A simplified receiver based Laurent decomposition (LD) for CPQPSK is proposed. CPQPSK signals can also be decomposed according to the LD theory. The optimum receiver and the simplified one for full response CPQPSK signals are designed based on LD. The latter is achieved by choosing several key filters in the matched filter bank for the optimum receiver. Computer simulations are performed on these simplified receivers. Simulation results show that the bit error rate performance of the simplified receiver with three matched filters can approach that of the optimum receiver with eight filters under a higher signal-to-noise ratio.

    Improved belief propagation algorithm for decoding of convolutional LDPC codes
    LIU Yuan-hua;WANG Xin-mei;HU Shu-kai;CHEN Ru-wei
    J4. 2009, 36(3):  424-447. 
    Abstract ( 2481 )   PDF (592KB) ( 1415 )   Save
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    A novel belief propagation (BP) decoding algorithm for convolutional low-density parity-check codes is proposed. The proposed algorithm raises the efficiency of updating the variable information by applying feedback information at each decoding iteration and employs the weighting factor to reduce the error propagation caused by the cycles in the Tanner graph, thus yielding a faster convergence of the decoding. Simulation results show that an error performance better than that of the existing belief propagation algorithm can be achieved, while the 5/8 decoding delay and the computation complexity are effectively reduced. Compared with the existing BP, the proposed algorithm achieves a gain of 0.16 dB at the BER of 10-6 with the same number of iterations.

    Equivalent keys of multivariate quadratic public key cryptosystem
    WANG Xin1;SUN Chen2;WANG Xin-mei1
    J4. 2009, 36(3):  428-432. 
    Abstract ( 1446 )   PDF (514KB) ( 1273 )   Save
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    The multivariate quandratic cryptosystem has the problem that many superflous private keys correspond to the same public key. By applying the Gauss Sustainer, the private key space is partitioned into equivalence classes. And then, a relationship between the number of elements in any equivalence private key class and plaintext (ciphertext) is established. This formula shows the number of private keys corresponding to any given public key is exponential. Hence, the private (further the public) key space is reduced greatly. Moreover, the normal form of affine transformations of the private key is derived. It has the sparse characteristic, which will reduce computing complexity and improve the storage efficiency. Finally, the R-SE(2) public key  signature scheme is taken for an example, and the security performance of this scheme affected by the step-structure is analyzed.

    Design research on the high-precision programming constant current driver of the white light LED
    LI Xian-rui1;LAI Xin-quan1;WANG Song-lin2;LI Yu-shan1
    J4. 2009, 36(3):  433-437. 
    Abstract ( 1778 )   PDF (867KB) ( 1404 )   Save
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    An accurate programmable constant current driver for the white light LED is designed. An autozero amplifier, based on the autozero technique, is constructed in the chip. The current delivered to the LED load is controlled by the external resistor and the enable pins. Three discrete constant current settings are available and may be selected at the supply voltage from 2.9 V to 4.4 V, which is up to 1 A. Measurement results show that the variation in the ratio of the external resistor current to the LED load current is less than 2.3%, when the LED load current changes from 200 mA to 800 mA. The driving current of 800 mA varies by less than 0.46% when the supply voltage changes by ±10%.

    Near-space platform aided passive tracking algorithm for super-low-altitude targets
    NIU Xin-liang1;ZHAO Guo-qing1;LIU Yuan-hua2;CHANG Hong1
    J4. 2009, 36(3):  438-442. 
    Abstract ( 2491 )   PDF (568KB) ( 1402 )   Save
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    A novel near-space platform aided passive location method for super-low-altitude targets using TDOA is proposed. The new method uses a near-space platform as the baseline in the height to form a redundant location system consisting of several subsystems. Each subsystem can obtain a set of location results with ambiguity. After eliminating the ambiguity by the nearest matching, the new method can improve the location accuracy in the whole observed airspace by SWLS fusion. A better tracking performance can be achieved by applying this method to starting the tracking for super-low-altitude targets and keeping the tracking through UKF. Simulation results show that the proposed method comes to stabilization within 50 s and that its tracking initial error can be reduced to the hectometer level with the measurement precision of 20 ns. But the traditional method requires 250 s to go to stabilization and its tracking initial error is greater than the kilometer level.

    Study of target recognition based on multi-sensor cooperating with exploration
    HU Guo-ping1,2;ZHANG Shou-hong1
    J4. 2009, 36(3):  443-447. 
    Abstract ( 2076 )   PDF (626KB) ( 2509 )   Save
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    Applying a Multi-sensor, such as optical, infrared, SAR, High-spectrum and electron signal type, to explore the target cooperating, a new approach is proposed based on the Neural Network together with the D-S evidence theory, and “orderly quantization” is adopted in target recognition. The target is classified extensively and then intensively. The approach can accurately and effectively identify the target.

    Band-edge optimization design of the quasi-elliptic filter
    ZHU Yong-zhong1,2;XIE Yong-jun1;XIE Wen-xuan3;LI Ya-feng1
    J4. 2009, 36(3):  448-467. 
    Abstract ( 1618 )   PDF (896KB) ( 1566 )   Save
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    A new technique is presented for maximizing the band-edge selectivity of elliptic filters, and then the equal ripple parameter of the quasi-elliptic function can be calculated when the band-edge selectivities of the elliptic function and quasi-elliptic function are the same. The quasi-elliptic function based on the method not only keeps the bandwidth invariable, but effectively narrows the transition band. Finally, a novel quasi-elliptic microstrip filter composed of four spiral stepped-impedance resonators (SIR) is designed. Measured results show that the filter acquires 15% size reduction and 20 MHz transition band reduction, but can also effectively inhibit the second and third harmonics.

    Two-isomorphic extending algorithm for regularity extraction in digital integrated circuits
    PAN Wei-tao;XIE Yuan-bin;HAO Yue;SHI Jiang-yi
    J4. 2009, 36(3):  452-462. 
    Abstract ( 1871 )   PDF (747KB) ( 1334 )   Save
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    To extract the regularity in digital integrated circuits, a novel algorithm is proposed. It can automatically identify and extract the subcircuit which appears frequently. By extracting and analyzing the properties of all two connected standard cells in the circuits, a series of templates including two standard cells will be obtained. The template with a high frequency will be extended so that it becomes longer than two, and then the instances of all longer templates will be explored using the proposed algorithm.To reduce the complexity and accelerate the algorithm, the matched vertexes will be deleted gradually from the search space. This algorithm has been implemented successfully in industrial projects, and has replaced the traditional manual analysis at the gate level. Furthermore, the complexity of the reverse analysis for VLSI is reduced, and the work efficiency can also be raised distinctly.

    IC robust optimization design using RSM
    YOU Hai-long;JIA Xin-zhang
    J4. 2009, 36(3):  458-462. 
    Abstract ( 1413 )   PDF (550KB) ( 1360 )   Save
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    Because of non-convergence and other problems the IC robustness design can not be achieved by only relying on the EDA simulation. A method is presented that uses the Response surface methodology (RSM) combined with EDA simulation designs, optimizes circuits for robustness, and is applied to the design of band-gap reference circuit. Through Hspice simulation and experimental design, the model of 3 objects and 4 parameters is built using 27 experiments. Based on the model the circuit is optimized for robustness. The optimized parameter sets satisfying the design targets make the circuit output more insensitive to the temperature variation.

    Fast Fourier transform algorithm for the combined integral equation to solve electrically large scattering problems
    CHEN Zeng-shuai;LAI Ben;HUANG Chun-ming;LIANG Chang-hong
    J4. 2009, 36(3):  463-467. 
    Abstract ( 1914 )   PDF (731KB) ( 1395 )   Save
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    A new fast Fourier transform-based algorithm is introduced for solving electrically large scattering problems. The entire computational domain is partitioned to near and far field couplings. The near field coupling can be computed by the traditional method of moments (MoM); while the impedance elements of far field coupling are characterized as a Toeplitz matrix by interpolating Green's function on a regular Cartesian grid, and the matrix-vector products are accelerated by fast Fourier transforms. Otherwise, the combined field integral equation (CFIE) eliminates the interior resonance problem suffered by the electrical field integral equation (EFIE) and the magnetic field integral equation (MFIE), and maintains the accuracy of the MoM. The iteration number for solving matrix equations is reduced to 10% that of EFIE.

    Design of the broadband dual-polarized probe array
    LI Yong;JIANG Hui;WANG Xiao-yi;LIU Zheng
    J4. 2009, 36(3):  468-479. 
    Abstract ( 1743 )   PDF (1162KB) ( 1491 )   Save
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    The probe arrays of the near-field measurement system is studied theoretically and experimentally. A dual-polarized linear array which consists of four dual-polarized printed dipoles is designed. First a dual-polarized printed dipole is designed as the unit of the array, which is composed of two vertical single polarized printed dipoles.Then a straight line array is composed of four dual polarized printed dipole antennas.The mutual couplings between array elements is analyzed. The isolation between the units is improved.Finally, the antenna array is measured actually. Measured results show that in a broader band, the isolations between the elements of the array are big while the mutual couplings between array elements are small, which indicates the validity of this method.

    Electromechanical coupled analysis of large broad band reflector antennas
    LI Peng;ZHENG Fei;JI Xiang
    J4. 2009, 36(3):  473-479. 
    Abstract ( 1662 )   PDF (664KB) ( 1453 )   Save
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    In the electromechanical coupled analysis of large broad band reflecort antennas, the mesh for structure analysis does not match the mesh for electromagnetism analysis, and diffrerent meshes are requied for diffreent frequencies. For these problemes, the GO method is used for modeling the electromechanical coupled model. A transformation matrix for different meshes has been deducted starting with the structure mesh. The number of nodes for electromagnetism analysis is ensured according to the frequency. This transformation matrix and improved Gaussian integral formula are used to analyze reflecort antennas. Compared with electromagnetism software, a fussy process for girding is avoidable, and much time is saved in computing. Compared with the traditional integral formula, an elevation in computing precision is obvious. Results of simulation demonstrate that the transformation matrix is very accurate and efficient, ant that it could be used in electromechanical coupled analysis of large broad band reflecort antennas. Finally, the mothod presented in this paper is used for a 40 m reflector antenna, with the result accord with practical engineering experience.

    Reliability of distributed storage systems
    ZHANG Wei1,2;MA Jian-feng2;YANG Xiao-yuan1
    J4. 2009, 36(3):  480-485. 
    Abstract ( 1986 )   PDF (557KB) ( 2952 )   Save
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    Based on invalid probability of storage nodes, a model is provided to evaluate the reliability of a given distributed information storage system. In this model, the reliability of a storage system is affected by 4 factors: time, invalidate probability of storage nodes, data distribution algorithm and storage policy. Such a model could partly solve the reliability problem in the system designing phase, and make data service more reliable.

    Optimal dynamic voltage selection algorithm for variable voltage processors
    LIU Hui;CHEN Ping;DU Jun-zhao
    J4. 2009, 36(3):  486-540. 
    Abstract ( 1369 )   PDF (644KB) ( 1224 )   Save
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    For battery-based embedded systems, how to save energy and extend the systems' life time is one of the most important problems. Existing research work considers the ideal processors that have a continuous variable voltage. However, practical processors only have discrete voltage levels. Therefore, for hard real-time embedded applications runing on practical dynamic voltage-scaling processors, this paper proposes an optimal voltage selection algorithm to obtain the minimum energy consumption of these applications without violating the given time constraint. Different from those existing heuristic algorithms, the energy-aware voltage selection problem is first formulized as a variation of the multiple-choice knapsack problem, and then an algorithm based on the dynamic programming technique is proposed to solve this problem. By comparing several voltage selection strategies on real embedding systems, experimental results show that our algorithm can obtain the minimum energy consumption without violating the given time constraint of the emmbedding application.

    Research on the Bayesian networks model in situation assessment
    CHAI Hui-min;WANG Bao-shu
    J4. 2009, 36(3):  491-495. 
    Abstract ( 1555 )   PDF (597KB) ( 1576 )   Save
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    The modular Bayesian network is proposed, which is utilized to assess the situation in the battlefield. According to the event and target action, the modular Bayesian network is dynamically constructed. In the process of inference for the Bayesian model, the inference result of combined Bayesian networks is considered as the soft evidence of the corresponding node in the present networks. Finally, a simple application of the method is described. The results show that the method is available and computationally efficient.

    Error diffusion halftone algorithm based on image segmentation
    WAN Bo;WANG Quan;GAO You-xing
    J4. 2009, 36(3):  496-546. 
    Abstract ( 1901 )   PDF (4803KB) ( 1496 )   Save
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    To reduce the visual artifacts produced by the conventional error diffusion algorithm in the digital halftone process, an error diffusion algorithm based on image segmentation is presented. In this algorithm the image segmentation technology is used to segment an image into two types of region. In one region, pixels have the same gray level while in the other they have a different gray level. In the halftone process, threshold modulation is only applied to the region which has the same gray level and at the same time the input dependent error diffusion coefficients which have four directions are used to process the halftone error. Experimental results show that our algorithm can reduce visual artifacts effectively and outperforms Floyd-Steinberg's error diffusion, Ostromoukhov's error diffusion and Bingfeng Zhou's error diffusion in the PSNR(Peak Signal Noise Ratio),WSNR(Weighted Signal Noise Ratio) and UIQI(Universal Image Quality Index) criteria.

    New method for clustering gene expression data
    WANG Wen-jun;ZHANG Jun-ying
    J4. 2009, 36(3):  502-534. 
    Abstract ( 1423 )   PDF (573KB) ( 1427 )   Save
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    A new clustering method based on the relationship between patterns is proposed. The relationship between patterns is obtained from gene expression data through the pearson correlation coefficient, which is denoted by a network, the relation feature between patterns is extracted by discovering the structure feature of the network, and clustering is performed in the relation feature space. The proposed method uncovers the dissimilarity between patterns belonging to different classes more effectively, and the dimensionality of the clustering space is so low than there is no need to reduce dimensions. The comparison of the method with the conventional ones shows that the method can obtain a much higher clustering efficiency than other methods and it can lead to a better efficiency even for those data with promiscuous distribution.

    New knapsack-type public-key cryptographic algorithm
    ZHANG Wei-dong;WANG Bao-cang;HU Yu-pu
    J4. 2009, 36(3):  506-511. 
    Abstract ( 2302 )   PDF (551KB) ( 1727 )   Save
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    A new knapsack-type public key cryptosystem is proposed, which is based on an easy knapsack problem. The cryptosystem is secure against Shamir's key-recovery attack in that it prevents the use of the super-increasing knapsack sequence in the construction of the cryptosystem. The cryptosystem is also invulnerable to the low-density subset-sum attack in that it obtains a relatively high density. It is shown that the cryptosystem withstands some brute-force attacks and the simultaneous Diophantine approximation attack. It only performs n addition operations for the cryptosystem to encrypt a plaintext, and the decryption algorithm only carries out n modular 2 divisions. Therefore, the cryptosystem is efficient with respect to the encryption and the decryption. Furthermore, the cryptosystem is suited for software and hardware implementations.

    Hyperspectral subpixel target detection approach based on expectation-maximization cluster
    LIU De-lian;WANG Bo;ZHANG Jian-qi
    J4. 2009, 36(3):  512-516. 
    Abstract ( 2306 )   PDF (1130KB) ( 2717 )   Save
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    Background is a key interferene in target detection. To avoid the interferene of complex background, an expectation-maximization cluster based approach to subpixel detection in hyperspectral is presented that incorporates background segmentation to model complex background. First, the expectation-maximization cluster model is employed to segment whole background into homogenous regions. Then the adaptive matched subspace detection algorithm (AMSD) is applied in each homogenous region. Since the segmented regions are more homogenous than the whole complex background, our new approach can have a better performance. Experimental result with a real hyperspectral image has proved the validity of the new approach.

    New study of polarimetric scattering of the two-dimensional sea surface
    LIU Wei;GUO Li-xin;WANG Rui;MA Jun
    J4. 2009, 36(3):  517-523. 
    Abstract ( 1963 )   PDF (1220KB) ( 7499 )   Save
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    A new method for simulating polarimetric scattering on the rough sea surface is studied based on the matrix of the Kirchhoff scattering facet. A two-dimensional sea surface is described as a height matrix and two slope matrices in the x and y direction, an expression for the scattered field with the elliptic polarized incidence wave is calculated in the Cartesian coordinate system by Kirchhoff approximation and the model of fully polarized RCS is obtained. Finally the fully polarized backscattering RCS and polarization signatures of the fractal sea surface are simulated for different conditions and the results are in accord with the characteristics of sea surface scattering. This method can be applied to many sea surface models because it uses discrete analysis on the two-dimensional model, which is important for the retrievement of sea polarimetric information.

    Novel broadband circular-polarized dielectric hemispherical helical antenna
    ZHANG Hou1;GONG Shu-xi2;XIA Dong-yu3
    J4. 2009, 36(3):  524-526. 
    Abstract ( 1771 )   PDF (601KB) ( 1621 )   Save
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    A novel bifilar constant-angle dielectric hemispherical helical antenna is developed. Its radiation properties are analyzed by the moment method with the curved basic and testing function, the curves of VSWR, polarization and pattern vs. frequency are presented, respectively. The calculated and measured results show that within the range of 800 MHz~2 600 MHz VSWR is less than 2, that AR is less than 3 dB, and that the relative bandwidth reaches 106%.

    Hyper-mutation antibody clone algorithms for TSP
    J4. 2009, 36(3):  527-534. 
    Abstract ( 2025 )   PDF (853KB) ( 1307 )   Save
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    According to the analysis of the affections of the coding strategies and the basic operators, including crossover and mutation, we find that the schema theory can not analyse the Genetic Algorithm very well when it is used to solve the Traveling Salesman Problems (TSP). Because the non-binary coding strategy and the crossover overly destroy the TSP path, the good schema of the parents can not be inherited effectively. In order to overcome the above shortcoming of the Genetic Algorithm, a new artificial immune system algorithm for TSP, Hyper-mutation Antibody Clone Selection Algorithm (HACSA), is put forward in this paper. A new triangle-based path representation is adopted, and some heuristic mutation strategies based on the triangle coding method are also designed. The antibody clonal selection theory of immunology is used to enhance the local search performance of the antibody. Both HACSA algorithm and the corresponding genetic algorithms are implemented to the typical traveling salesman problems respectively. Experiments indicate that HACSA, behaving as an evolutionary strategy, is shown to be capable of solving complex machine learning tasks effectively like TSP. The experimental results show that HACSA can achieve or exceed the known optimal solution in over 60% problems, but that almost all the corresponding immune system algorithms and genetic algorithms fall into the local maximum, and they can not lead to the satisfied solutions.

    Efficient embedded image coding combined with morphological dilation and difference reduction
    GAO Shan;ZHANG Ming;BI Du-yan;XU Yue-lei;MA Shi-ping
    J4. 2009, 36(3):  535-540. 
    Abstract ( 1527 )   PDF (617KB) ( 1374 )   Save
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    A novel wavelet image coder is proposed according to both cluster characteristic of intra-subband significant wavelet coefficients and inter-subband similarity. The algorithm utilizes two different structuring elements for morphological dilation to extract and encode the subband clustered significant coefficients, and it can solve the conflict between dilation speed and dilation quality when using the single structuring element. The difference reduction is used to encode the position of start position in each cluster and sparse coefficients, which can improve the coding efficiency of the insignificant coefficients. Furthermore, the algorithm uses the parent-children relationship to reduce the correlation between wavelet coefficients across subbands, while elaborately designed adaptive arithmetic coding can further reduce code redundancy. As a kind of embedded coder, the algorithm is also rate scalable. Experimental results show that the performance of the new coder is superior to the SPIHT and EBCOT, and outperforms the non-embedded morphology coders MRWD and SLCCA.

    Effective algorithm of parallel twiddle factor generation for programmable FFT processing and its implementation
    LIU Hong-xia;YANG Liang;HUANG Jin;HUANG Shi-tan
    J4. 2009, 36(3):  541-546. 
    Abstract ( 5052 )   PDF (551KB) ( 1496 )   Save
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    In order to resolve the problem of high complexity and high area consumption in designing a twiddle factor address generator that generates three addresses in every clock cycle, this paper presents a new storage and access strategy of twiddle factors based on the Multi-bank memory structure. The strategy guarantees that the three twiddle factors needed by a butterfly computation of mixed-radix 4/2 FFT algorithm can be accessed simultaneously without conflict. This twiddle factor generating algorithm based on one lookup table for an arbitrary size FFT is dependent only on its maximum size that can be processed. At the same time, the transition from one stage to another can be implemented with a shift addend register. Therefore, this algorithm can be implemented with less complexity and area consumption than any other existing design. In addition, the number of accesses to one of those banks and its size are reduced by at least 50 percent.

    Self adaptive network topology inference algorithm in tomography
    ZHAO Hong-hua;CHEN Ming;WEI Zhen-han
    J4. 2009, 36(3):  547-552. 
    Abstract ( 1523 )   PDF (603KB) ( 1213 )   Save
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    There are a few network topology inference techniques based on network tomography, but all of them use only one network performance characteristics, which leads to many limits when the network load is different. In order to reduce the limits of the inference based on one network performance characteristics, a self adaptive network topology inference method is proposed which joines multiple network performance parameters self-adaptively in inference. In applying the self adaptive network topology inference, no additional traffic is needed except for some calculation, and the inference method could be applied in complex networks with different loads. The self adaptive method is analyzed theoretically and validated through simulations by NS2, and the results of simulation illustrate that the self-adaptive inference method could infer network topology correctly when faced with networks whose load changes greatly.

    Iterative channel estimator using superimposed training
    SHI Zhe
    J4. 2009, 36(3):  553-556. 
    Abstract ( 1382 )   PDF (541KB) ( 1544 )   Save
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    Because of high bandwidth efficiency and low complexity, channel estimation based on superimposed training (ST) has received wide considerations in recent years. In this paper, a new iterative method for channel estimation is proposed based on the ST method. Using the improvement from symbol estimation after thresholding, received sequences and estimation of channel state information are used to do iterative computation in the receiver. Computer simulations show that the mean square error (MSE) and bit error rate (BER) can be reduced by an order of magnitude with the signal-to-noise ratio around 15 dB after 3~4 iterations.

    Design of the low-noise high-speed differential charge-pump phase-lock loop
    LIU Hong-yan1;LUAN Xiao-feng1;LIU Chuan-jun2
    J4. 2009, 36(3):  557-562. 
    Abstract ( 1660 )   PDF (928KB) ( 1592 )   Save
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    A high-performance Charge Pump Phase Lock Loop(CPPLL) of low-noise high-speed is presented. The all-differential structure is used in design; Two kinds of high-speed low-power consumption logic circuits—CMOS and Current Mode Logic(CML) are introduced to compose the operation unit; the proposed differential charg-pump loop-filter saves the die area observably. The entire circuit is implemented in the 0.6 μm BiCMOS process. Results from HSPICE simulation show that the power dissipation is  77 mW, that the center-frequency is 223 MHz, and that the frequency range is 102 MHz~800 MHz. The specifications are satisfied and the characteristics such as noise, speed, and power consumption are optimized remarkably.

    Design and performance analysis of quasi-orthogonal space-time block codes for four antennas
    XIE Wu1;CAO Jia-nian1;WANG Li-ying2
    J4. 2009, 36(3):  563-572. 
    Abstract ( 2180 )   PDF (517KB) ( 2595 )   Save
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    This paper analyzes the structure and characteristics of several types of quasi-orthogonal space-time block codes (QSTBC). It proposes two new methods for QSTBC for four antennas which enrich the family of QSTBC. Experimental results indicate that the two new QSTBC have good performance as in TBH and Jafarkhani cases, while the decoding complexity is the same as that of other QSTBC. This paper has compared the Maximum Likelihood (ML) decoding algorithm and QR decomposition decoding algorithm for the new QSTBC. Simulation results indicate that the QR decoding algorithm has good performance and can reduce the computation complexity.

    Design of a compact narrow band-pass filter with harmonics suppression
    ZHAO Jian-zhong;YANG Jin-ping;YANG Guo;WU Wen
    J4. 2009, 36(3):  568-572. 
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    A compact narrow band-pass filter with a low insertion loss and multi-order harmonics suppression is proposed. The harmonic suppression is realized through transmission zeros of the parallel coupled lines loaded open-circuited resonator, and the filter passband characteristics are determined by the short-circuited stubs. By coupling of the transmission line model of this filter and even- and odd-mode analysis, the expressions for calculating element parameters are presented, and thus the design process in this paper is fast and accurate. Finally, a band-pass filter working in 2.4 GHz is developed. Simulation and measured results show that the passband insert-loss is 0.4 dB, that stopband attenuations at second and third harmonics frequency are more than 35 dB, and that stopband attenuations at fourth is about 20 dB.