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    20 October 2009 Volume 36 Issue 5
      
    Original Articles
    Intercarrier interference cancellation for MIMO-OFDM systems
    J4. 2009, 36(5):  761-766. 
    Abstract ( 1965 )   PDF (643KB) ( 1441 )   Save
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    We develop a model for the multiple-input multiple-output orthogonal frequency division multiplexing(MIMO-OFDM) system over time varying frequency selective fading channels. Using this model, we analyze the impacts of the channel on time variation characteristics within a transmission block which destroy the orthogonality of subcarrier and cause serious intercarrier interference(ICI). To circumvent this problem, we propose a frequency-domain iterative ICI cancellation algorithm. By separating the channel transfer function matrix into data and the ICI part, data are initially obtained by the zero-forcing algorithm, the interference between adjacent subcarriers, created by ICI matrix, is then subtracted from received symbols and finally the parallel interference cancellation detection using the data matrix is performed to suppress the multistream interference from different antennas. By restricting the interference to eighteen neighboring subcarriers, under the condition that the performance loss is neglectable compared with the original method, computational complexity can be drastically reduced. Simulation results show that the proposed method can effectively mitigate the effect of ICI at different doppler shifts and approach the ICI-free performance at a low signal-to-noise ratio.

    Blind equalization algorithm for the QOTDM system in multi-path fading channels
    WANG Jie-ling;LIU Zu-jun;YANG Hong;YI Ke-chu
    J4. 2009, 36(5):  767-770+787. 
    Abstract ( 1639 )   PDF (620KB) ( 1287 )   Save
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    An efficient blind equalization scheme for the Quasi-Orthogonal Time Division Multiplexed (QOTDM) system is presented. At the transmitter, the transmitted signal with a white frequency spectrum can be obtained by adding one group of QTODM sample sequences with a frequency shift to the other group, and the receiver can get two group sample sequences by filtering the received signal and the received signal with a frequency shift using a comb filter. Firstly, two groups of sample sequences are equalized blindly by the modified constant modulus algorithm (MCMA), then the output of the primary equalizer is equalized by MCMA before the deferent error is larger than the gate, and finally the equalizer adopts the algorithm of lease mean square combined with the decision feedback technique. After equalization, the inter symbol interference (ISI) can be cancelled. It is shown by Monte Carlo simulation that the new scheme can cancel the “ground effect” of the QOTDM system in the ground-air multi-path fading channel. When the Rice fading factor is 10dB, the signal-to-noise ratio of 4dB or so for SER of 10<sup>-3</sup> can be achieved by the scheme proposed compared with OFDM.

    Fast estimation of inner-code information in the DVB-S receiving system
    LIU Jian;WANG Xiao-jun;ZHOU Xi-yuan1,3;XIE Nuo
    J4. 2009, 36(5):  771-776. 
    Abstract ( 1473 )   PDF (585KB) ( 1135 )   Save
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    Based on the transcendent parity-check vector of convolutional coding, a fast algorithm for estimating inner code information in the DVB-S (digital video broadcast satellite) receiving system is proposed. Under the condition of a high bit error rate, the transcendent parity-check vector is used to estimate the inner code; under the condition of a low bit error rate, the parity-check vector computed with the fast algorithm is used to estimate the inner code. Simulation experiment shows that by using the proposed algorithm the estimating time can be reduced to 10% that of the traditional algorithm with the reliable estimation.

    Filter lookup table with a frequency predistorter structure for the memory nonlinear power amplifier in the OFDM system
    REN Zhi-yuan;ZHANG Hai-lin
    J4. 2009, 36(5):  777-781. 
    Abstract ( 1697 )   PDF (692KB) ( 1525 )   Save
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    A new structure based on the Filter Look-Up Table(FLUT) structure is proposed for solving the problem of frequency-selective nonlinear distortion of the power amplifier in a wideband OFDM system. A new predistorter which uses the 2-dimensional Look-Up Table method is added in the frequency domain to compensate the distortion more accurately. Simulation result indicates that the system performance and the accuracy of convergence can be improved, and that the rate of convergence can be increased by 50% compared to the original FLUT structure.

    Rate-compatible  codes based on puncturing parity check bits in group
    GUO Kai;CHEN Yan-hui;LI Jian-dong
    J4. 2009, 36(5):  782-787. 
    Abstract ( 1558 )   PDF (808KB) ( 1216 )   Save
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    A new class of rate-compatible (RC) punctured codes with linear encoding complexity based on the punctured multiple accumulated crossover parallel-concatenated SPC (M-ACSPC) codes are proposed. The parity check bits are grouped according to the order of the branch where they are generated in the mother codes. The puncturing priority for each group is determined by the density evolution using a Gaussian approximation. Different groups of parity check bits are punctured to implement RC-M-ACSPC codes at different code rates. Simulation results show that the RC-M-ACSPC codes proposed have a better bit-error-rate performance over a wide code rate range than punctured RC codes based on (3,6) regular LDPC codes.

    Method for improving the uplink capacity of an integrated high altitude platform station-terrestrial CDMA system
    WANG Jun;YI Ke-chu;TIAN Bin;LIU Zu-jun
    J4. 2009, 36(5):  788-792. 
    Abstract ( 1314 )   PDF (722KB) ( 1144 )   Save
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    According to the characteristic that the inter-cell interference factor of the HAPS CDMA system is lower than that of the terrestrial CDMA system, the disadvantage of the ring structure is pointed out and an improved multi-layer structure is proposed in which two adjacent terrestrial layers are seperated by several HAPS layers. The uplink capacity formula for the HAPS-terrestrial CDMA system is deduced and the capacity of the ring structure and that of the multi-layer structure are compared. Numerical results show that the uplink capacity of the HAPS system and that of the terrestrial system of the multi-layer structure increase to 111.9 and 110.2 respectively for a 10-tier system, while the uplink capacity of HAPS system and that of the terrestrial system of the ring structure are only 97.4 and 97.6 under the same condition.

    New kernel learning method to improve radar HRRP target recognition and rejection performance
    CHAI Jing;LIU Hong-wei;BAO Zheng
    J4. 2009, 36(5):  793-800. 
    Abstract ( 1905 )   PDF (655KB) ( 1278 )   Save
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    Radar high-resolution range profiles (HRRP) satisfy typical multimodal distribution. In radar HRRP target recognition and rejection, it is difficult to utilize a singe Gaussian kernel to describe the multimodal distribution. According to this, support vector data description (SVDD) was expanded from a single Gaussian kernel to a linear combination of multiple Gaussian kernels and then this combination is used to treat the recognition and rejection problem. Based on different degrees of freedom on the combinational coefficients, the resulting Multi-kernel SVDD could be expressed as different convex optimization problems: SOCP or SDP, and both of them could be solved with global optimal solutions. The proposed method employs more complicated kernel formations, and it can describe the multimodal distribution of HRRP data more flexibly in the high-dimensional feature space so as to improve the recognition and rejection performance. Experimental results show that the loss value of the new method is just 88.6%~93.2% that of the single kernel SVDD.

    Wide swath imaging with multidimensional waveform encoding
    WU Qi-song;JING Wei;XING Meng-dao;BAO Zheng
    J4. 2009, 36(5):  801-806+845. 
    Abstract ( 1920 )   PDF (868KB) ( 1374 )   Save
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    A novel approach described in the paper is the Wide Swath Imaging with Multidimensional Waveform Encoding Based on Multiple-Input Multiple-Output Synthetic Aperture Radar (MIMO-SAR). First, the concept of Multidimensional Waveform Encoding is introduced; then in the process of signals transmission, arrays in elevation is used to generate beamforming to scan different subswaths, and they can properly design the system parameters in order to restrict time-delay of the echoes from the near subswaths to the far sub-swath, As a result, the radar echoes from different subswaths would overlap in the receiver; range ambiguities must occur; finally digital beamforming is used to remove range ambiguities. The approach can be used to realize consecutive wide swath, and it overcomes the disadvantage that non-consecutive wide swath occurs by the conventional elevation multi-beam. At the same time it holds the abilities of flexible power distribution and of the multiple range resolution. It not only overcomes the shortcoming of low echoes power which appears in traditional wide swath imaging, but also breaks through the disadvantage of single range resolution in the processing of traditional imaging.

    Pattern synthesis method for array efficiency maximization
    LIU Xiao-li;LIAO Gui-sheng;ZENG Cao
    J4. 2009, 36(5):  807-812. 
    Abstract ( 2085 )   PDF (605KB) ( 1434 )   Save
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    The objective of many pattern synthesis methods, either based on the adaptive array theory or on template approximation, is often the shape control of pattern rather than the array efficiency. In order to solve the problem, a novel algorithm for pattern synthesis is presented by minimizing the norm of the weight vector under constraints of the mainlode-sidelobe-ratio, mainlobe width, flat mainlobe or interference nulling. Simulation results demostrate the validity of the proposed method.

    Deception-jamming technology against the SAR based on the deceptive scene and real-time analyses
    SUN Guang-cai;ZHOU Feng;XING Meng-dao;BAO Zheng
    J4. 2009, 36(5):  813-818+866. 
    Abstract ( 2362 )   PDF (1106KB) ( 1195 )   Save
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    Considering the motion error of the enemy SAR, this paper proposes a novel realtime approach of deception-jamming. Via quick algorithm, this method pretreats the deception picture first, and then does the convolution operation with the received signal and transmits the signal. In this way, the distance between SAR platform and jamming equipment can be simulated effectively, and the echos contain the motion information. After motion compensation and SAR imaging operation, a more lifelike image can be obtained. This method proposes a quick algorithm of deceptive scene signal generation based on two-step processing, which ensures realtime generation of the signal. Simulation and experimental data have proved the validity of the approach.

    Performance analysis of MIMO radar DOA estimation
    YANG Wei;LIU Zheng
    J4. 2009, 36(5):  819-824. 
    Abstract ( 1942 )   PDF (638KB) ( 1334 )   Save
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    The Cramer-Rao Bound(CRB) for MIMO radar DOA estimation with co-located arrays in a single target scenario is derived, which shows that CRB depends on both the steering vectors of transmit/receive arrays and the correlation matrix of transmitted waveforms. Compared with traditional phased array radar, MIMO radar has a better DOA estimation performance for most angles. CRB can be further reduced by increasing the spaces between transmit array elements in the MIMO radar system so that MIMO radar can obtain a much better DOA estimation performance than phased array radar. Simulation results validate above conclusions.

    New algorithm for high-speed spinning target 3D ISAR imaging
    HE Bo-sen;ZHANG Lei;ZHANG Long;XING Meng-dao;BAO Zheng
    J4. 2009, 36(5):  825-830+915. 
    Abstract ( 1558 )   PDF (1047KB) ( 1270 )   Save
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    A 2D spectrum matched filter banks based 3D ISAR imaging algorithm for a target in high speed spinning is proposed. Each spectrum matched filter bank yields a focused slice for corresponding scatterers. By extracting the spatial parameters from all the slices, the 3D image of the target can be constructed. The existing GRT and EHT based algorithm is low in efficiency since the projection procedure is carried out scatterer by scatterer. However, our approach is based on the matched filtering theory, and by applying FFT, it has a low computational load. Numerical simulation confirms the validity of the algorithm.

    Novel X-band dual-mode bandpass filter based on the substrate integrated waveguide
    QIN Pei-yuan;SHI Xiao-lin;LIANG Chang-hong;WU Bian
    J4. 2009, 36(5):  831-834. 
    Abstract ( 1626 )   PDF (639KB) ( 1498 )   Save
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    This paper presents a novel dual-mode filter with symmetric transmission zeros based on the substrate integrated waveguide(SIW). This filter contains two dual-mode SIW rectangular cavities. By making use of the inductive discontinuities in an SIW cavity, two coupling degenerate modes can be excited. Due to the phase difference between the two modes in each cavity, two transmission zeros on each side of the passband are created, so the out-of-band rejection of the filter is significantly increased. An SIW dual-mode filter with a center frequency of 12GHz has been fabricated and measured using the proposed method. Experimental results agree well with the simulation results.

    Improved particle swarm optimization and its application for conformal array pattern synthesis
    LI Wen-tao;LIU Shu-fang;SHI Xiao-wei;HEI Yong-qiang
    J4. 2009, 36(5):  835-840. 
    Abstract ( 2509 )   PDF (1421KB) ( 1393 )   Save
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    By means of introducing such improved techniques as velocity updating, exceeding boundary control, perturbation of the global best particle, a new improved particle swarm optimization (IPSO) algorithm is proposed, which is further combined with the simplified quadratic interpolation method to overcome the drawbacks of the standard particle swarm optimization (PSO) algorithm, such as slow convergence, prematurity and easily trapping in local optimum. A modified Bernstein polynomial is used to reduce the number of variables when calculating the pattern function of the spherical conformal array. Simulation results show that the pinpointing search ability and the global search ability of the proposed algorithm are significantly improved compared with the standard particle swarm optimization and genetic algorithm (GA), thus proving the effectiveness of the proposed algorithm for antenna synthesis.

    Novel SCRLH transmission line structure and its application to UWB filter design
    GONG Jian-qiang;CHU Qing-xin
    J4. 2009, 36(5):  841-845. 
    Abstract ( 1851 )   PDF (876KB) ( 1264 )   Save
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    A novel simplified composite right/left-handed (SCRLH) transmission line (TL) structure is proposed. The dispersion and impedance characteristics of the novel structure are first analysed based on the Bloch theory, which shows that the attenuation constant remains zero with a relatively smoother characteristic impedance distribution within the passband and that the characteristic impedance is purely imaginary with inhibition of the electromagetic wave propagation outside the passband. Based on the above analysis, the methodology for synthesizing the bandpass filter by utilizing the novel structure is further proposed, which is then adopted to design an ultra-wideband (UWB) filter with the center frequency of  6.85 GHz and the fractional bandwidth of 110%. A good agreement among the circuit simulation, fullwave simulation and experimental results justifies the theoretical analysis and the synthesis method presented in the paper.

    Solving electrically large EM problems using parallel FDTD and HP blade server
    LEI Ji-zhao;LIANG Chang-hong;ZHANG Yu
    J4. 2009, 36(5):  846-850. 
    Abstract ( 1747 )   PDF (1224KB) ( 1256 )   Save
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    In order to make full use of the performance of the parallel FDTD method based on the blade serve, the radiation patterns in the far field of two ultra short wave antennas mounted on a ship model are calculated. The results are obtained by different cores and various virtual topologies. Then after analyzing the influence of topology schemes on parallel performance of Parallel FDTD on the blade serve, the paper presents the best MPI virtual topology for Parallel FDTD based on the blade serve. Finally the RCS of F117 is calculated at 2GHz. A mount of memory is needed for the problem but the FDTD based on the PC cluster can not be used to solve that.

    Auxiliary excitation algorithm of the domain decomposition method for 3-D large-scale electromagnetic problems
    Lü Zhi-qing;AN Xiang
    J4. 2009, 36(5):  851-856. 
    Abstract ( 1421 )   PDF (889KB) ( 1232 )   Save
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    A novel domain decomposition method (DDM) without resonance based on an auxiliary excitation algorithm is developed for the simulation of three-dimensional (3-D) large-scale electromagnetic problems. To decrease the computational scale and complexity, the original domain is partitioned into several nonoverlapping subdomains. A set of Robin-type auxiliary excitations on the inter-domain interfaces has been introduced to exchange information between subdomains. Because each subdomain can be tackled independently with the vector finite element method, the originally large problem is reduced to a much smaller interface problem. The proposed method becomes very efficient for finite periodic problems by introducing basic subdomains to describe the geometric repetitions.

    Two efficient algorithms for joint diagonalization with exception of the singular solution
    ZHANG Wei-tao;LIU Ning;LOU Shun-tian
    J4. 2009, 36(5):  857-861. 
    Abstract ( 1646 )   PDF (533KB) ( 1401 )   Save
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    Two improved efficient algorithms are proposed to reduce the computational load for non-orthogonal joint diagonalization free of singular solutions. In the first improved algorithm, the determinate of the diagonalization matrix is expanded by its current updating column to avoid matrix inverse operation in this computational phase. The other improved algorithm is developed by QR factorization of the column exchanged diagonalization matrix, whose determinate is computed by the product of the diagonal elements of the resulting upper triangular matrix. As a result, the improved algorithms exhibit a low computational load since both of them reduce one matrix inverse operation in comparison to the original one. Finally, numerical simulation results show that the two improved algorithms have a computational load equal to 18.9% and 13.5% that of the original algorithm when the objective matrices are of large dimension and number.

    High precision passive TDOA location method for low-altitude targets
    NIU Xin-liang;ZHAO Guo-qing;LIU Yuan-hua;CHANG Hong
    J4. 2009, 36(5):  862-866. 
    Abstract ( 1538 )   PDF (796KB) ( 1549 )   Save
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    An improved passive TDOA location method is proposed. The novel method uses the elevation angle of the target as a new measurement to form a redundant location system consisting of three subsystems. Each subsystem can obtain a set of location results with ambiguity. A better performance can be achieved after eliminating the ambiguity by the nearest matching and processing the location results by SWLS fusion. Simulation results show that the proposed method has almost the same precision as the usual method for the high-altitude targets; however, it has a much higher precision for the low-altitude targets.

    Analysis and design of novel ESD protection circuit in 0.18μm CMOS process
    LIU Hong-xia;LIU Qing-shan
    J4. 2009, 36(5):  867-870+926. 
    Abstract ( 1562 )   PDF (607KB) ( 1292 )   Save
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    Based on the 0.18μm CMOS process, a new type of power-rail ESD protection circuit for protecting the gate of the ESD clamp device is proposed. An NMOS feedback device is added in the detection circuit, and the dynamic transmission structure is applied. The working states are enhanced by the feedback structure, which can shutdown the protection circuit immediately, reduce the hold time of the current across the gate of the clamp device, and protect the gate. This circuit uses the normal devices for the 0.18μm CMOS process, thus saving the cost greatly. The effectiveness of this new protection circuit is verified by the research results.

    Study of the reduction algorithm of SOC inter-core  interconnects for testing
    SHANG Yu-ling;LI Yu-shan
    J4. 2009, 36(5):  871-876+956. 
    Abstract ( 1384 )   PDF (784KB) ( 1188 )   Save
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    With the manufacturing technology and operation frequency of VLSI entering the era of DSM and GHz, the crosstalk of SOC inter-core interconnects can not be ignored anymore. A reduction algorithm for core-external interconnect is presented based on characteristics of the interconnect bus of SOC. Any topology of inter-core interconnects is described first and an interconnect relationship tree is built. Unwanted aggressive interconnects could be cut off according to the accuracy of test. Interconnects with the tri-state and bi-direction driving source are sifted according to the mutex algorithm. Test patterns are generated for these interconnects after sifting according to the TPG algorithm. The test set is decreased and test efficiency is improved.

    Combinational equivalence checking based on AIG reasoning
    J4. 2009, 36(5):  877-884. 
    Abstract ( 1536 )   PDF (563KB) ( 1179 )   Save
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    Most SAT based combinational equivalence checking algorithms combine two circuits into a miter, and then convert the miter into a CNF formula. After that, an SAT solver is invoked to check whether the CNF formula is satisfiable. However, when a miter is converted into a CNF formula, the structure information of the circuit is lost. In this paper, we assume the output of the miter is 1, and then the backtracking method is used for conflict checking to decide the satisfiability of the miter. By using the character of AIG, four input combinations of each node can be reduced into one to simplify the deducing procedure. Preliminary experiments demonstrate the efficiency of our approach.

    Research on the optimal percentage miter of the microstrip right angle bend
    LU Hong-min;WU Bao-yi;YAO Zhi-cheng;WAN Lian-cheng
    J4. 2009, 36(5):  885-889. 
    Abstract ( 1635 )   PDF (751KB) ( 1826 )   Save
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    In a high-speed circuit, microstrip characteristic impedance discontinuity caused by the right angle bend of PCB traces affects the quality of the signal transmission seriously. The numerical results of the impact of microstrip structure parameters and relative dielectric constant on the optimal percentage miter M of trace right angle bend with a 45°out miter are obtained. Based on the principle of least squares, the formula for M versus the width-to-height ratio w/h is presented by fitting the numerical results with MATLAB. Similarly, the linear expression for M versus the relative dielectric constant is also presented for the 50Ω line. The results show that the trace right-angle bend with a 45°out optimal percentage miter makes the quality of the signal transmission best. And the impact of relative dielectric constant and thickness of microstrip on M is not obvious, but the impact of w/h on M is significant.

    Research on finding annihilators of Boolean functions based the algebraic normal form fast transformations
    LIU Fu-yun;XIAO Hong;XIAO Guo-zhen
    J4. 2009, 36(5):  890-895. 
    Abstract ( 1748 )   PDF (528KB) ( 1190 )   Save
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    The algebraic normal form fast transfermations(ANFFTs) and computing methods are proposed by using the properties of Boolean Function's algebraic normal form, which has the smallest memory and higher efficiency. Under the previous assumption, two efficient algorithms for computing the annihilators of Boolean functions are presented. The first algorithm can be used to find the algebraic immunity of Boolean functions on n-variables and the algebraic normal form of the annihilators with the lowest algebraic degree. The second algorithm can be used to compute the algebraic immunity of a balanced Boolean functions on n-variables and its annihilators which have the algebraic degree≤d. Compared with the algorithms for computing the annihilators by solving linear congruential equations, these methods are highly operable and can be used to assess more effectively the resistance of Boolean functions against algebraic attacks.

    Dynamic pull-in of magnetostatic micro-devices
    GUO Yong-xian;JIA Jian-yuan;ZHANG Da-xing
    J4. 2009, 36(5):  896-901. 
    Abstract ( 1343 )   PDF (791KB) ( 1190 )   Save
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    The analysis of the pull-in of magnetostatic micro-devices (MMD) has been done using quasi-static assumptions traditionally. The models established are not exact enough because of the dynamic characteristics of the devices. So it is necessary to establish the dynamic models, which will be more suitable to the normal and could help the design and control of the micro-devices. Based on the energy balance equations, the dynamic pull-in characteristics of two MMD with the step input magneto motive force are analyzed, with the reluctance of the magnetic core m considered and the effect of system damping neglected. The results indicate that as to the parallel-plate device, the critical dynamic pull-in displacement of the mobile part is 1.5 times that when quasi-static pull-in occurs; as to the torsional device, the critical dynamic pull-in angle increases with the decrease of m, and changes from 1.29 to 1.46 times that when quasi-static pull-in occurs. The critical step inputs MMF of the two MMD are about 91.9% and 91.2% the quasi-statically predicted pull-in MMF of each MMD respectively.

    Deadlock prevention approach for a class of timed Petri nets
    J4. 2009, 36(5):  902-908. 
    Abstract ( 2129 )   PDF (677KB) ( 1259 )   Save
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    To solve the problem of deadlock prevention for timed Petri nets, an effective prevention policy based on siphons is proposed. Without enumerating the reachable markings, deadlock prevention is achieved and the final supervisor is live. First, a timed Petri net is stretched into an SPN. Without influence on the system performance, each transition in the SPN has a unit time delay. Then by ignoring the factor of delay time, the siphon-control-based approach is applied. Monitors based on the marking constraints are added to the plant model to ensure all strict minimal siphons in the net invariant-controlled. A liveness-enforcing supervisor with a simple structure can be realized by reverting the TPN.

    Reliability analysis for the deployment mechanism of a large satellite antenna based on unascertained information
    J4. 2009, 36(5):  909-915. 
    Abstract ( 1872 )   PDF (816KB) ( 2091 )   Save
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    The deployment principium of a large hoop-truss satellite antenna is studied and the mechanical analytical model and the unascertained reliability model of its deployment mechanism are presented. Synthetically considering the effect of dimension errors and the space environment factors, we treat the mechanism movement as a function of some unascertained rational numbers, and derive the reliability formula by using the computational theorem of unascertained rational numbers. The movement reliability of the mechanism of a large satellite antenna in the whole spreading process is predicted. Compared to the mature random method, the proposed method can obtain reliability result of safer and higher faith degree in the case of inadequate data or insufficient information; moreover, it is simple and easy to apply. Finally the possible values and faith degrees of the performance function of the unascertained antenna deployment mechanism are obtained by an example, which illustrates the rationality and feasibility of the presented method.

    Study of safety factors and non-probabilistic reliability measures of structures
    J4. 2009, 36(5):  916-920. 
    Abstract ( 1747 )   PDF (554KB) ( 1913 )   Save
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    The safety factors, the non-probabilistic reliability measures and their interrelations are investigated, when interval variables are utilized to describe the uncertain parameters of structures. First, three kinds of safety factors named central, non-probabilistic and interval factors are discussed. Then a comparison between two kinds of non-probabilistic reliability measures, which are reliability index and set-theoretic reliability measure, is made. Finally, the functions of the safety factors and the non-probabilistic reliability measures are established. The results extend the non-probabilistic design theory of structures.

    Tropospheric zenith path delay measured by a single ground-based undifferenced GPS receiver
    ZHU Qing-lin;WU Zhen-sen;ZHAO Zhen-wei
    J4. 2009, 36(5):  921-926. 
    Abstract ( 2040 )   PDF (969KB) ( 1288 )   Save
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    The GPS-measured tropospheric zenith path delay(ZPD) plays a key role in atmospheric sciences, the numerical weather forecasting, and so on. Differential GPS technology is widely used in GPS-measured ZPD, but this technology has some drawbacks, such as inefficiency, high cost and low removability. However, undifferenced GPS does not suffer from these drawbacks. The tropospheric zenith path delay in Shanghai is measured by precise point positioning (PPP) and a new stochastic model using the satellite elevation angle-based cosine function. The quality of the PPP-derived ZPD is examined through comparison with two independent datasets: nearby radiosonde records and the estimation by GIPSY. It is found that the PPP-derived ZPD agrees well with results of GIPSY and radiosonde, with the Root Mean Square Error (RMS) value and mean bias being in the range of centimeter level. Consequently, it is feasible to measure the tropospheric zenith path delay by a singular ground-based undifferenced GPS and PPP's accuracy is nearly equal to the accuracy of GIPSY.

    New method for coding quality assessment of the stereo remotely sensed imagery
    LI Shi-zhong;HU Xin;GU Xue-mai;Lü Yuan;WANG Yu
    J4. 2009, 36(5):  927-932. 
    Abstract ( 1463 )   PDF (620KB) ( 1398 )   Save
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    The method for coding quality assessment of the remotely sensed imagery plays an important role in studying the compression algorithm of the remotely sensed imagery. A new coding quality assessment objective method for the stereo remotely sensed imagery, which is based on the characteristics of the images and the practical application in the stereo mapping, is presented in this paper. The mathematical model of coding quality objective assessment of the stereo image is established by taking full account of the stereo image distortion caused by the four main factors: the radiometric character distortion, texture distortion, loss of correlation and geometrical character distortion. Experimental results show that this method is superior to the common methods such as MSE(Mean Square Error) and PSNR(Peak Signal to Noise Ratio). By using this method, a satisfactory result has been obtained, which is consistent with that from the human visual perception. And the method has strong correlation with the subjective method MOS(Mean Opinion Score).

    High-level power optimization method for multiple supply voltage  using  the multi-objective genetic algorithm
    SUN Qiang;SUN Xing-qi;MA Guang-sheng
    J4. 2009, 36(5):  933-939. 
    Abstract ( 1866 )   PDF (756KB) ( 1170 )   Save
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    This paper proposes a time-and-area-constrained high-level power optimization method for a multiple supply voltage, in which operation scheduling and functional unit allocating are simultaneously done through the genetic algorithm. Invalid chromosomes caused by time and area constraint are avoided by treating constraint optimization as a two-objective optimization function: one objective is the original objective function and the other is the degree violating the constraint conditions, thereby avoiding the influence of constraint conditions on the problem solving. The problem of invalid chromosomes caused by data dependence is solved through one point crossover operator based on data dependence. Experimental results show that this algorithm has improved power optimization by 10% and the convergence rate by 15%, compared with those simple power optimization methods for a multiple supply voltage of the genetic algorithm which does not consider invalid chromosomes handling.

    Fast decoding algorithm for differential space-time-frequency codes
    WEI Na;LIU Wen;XIE Wu;LI Tie-cheng
    J4. 2009, 36(5):  940-944. 
    Abstract ( 1676 )   PDF (562KB) ( 1144 )   Save
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    The decoding complexity of conventional differential space-time-frequency codes based on maximum-likelihood (ML) differential detection increases quickly with the number of constellation components and transmitted information symbols. By grouping the constellation, a fast decoding algorithm is proposed. The proposed algorithm provides performance close to that of the ML differential detection, that is, both can achieve maximum space-multipath diversity, but the proposed algorithm offers a lower decoding complexity. Analytical evaluation and corroborating simulations reveal its performance merits.

    Design of the 2-dimensional test patten compression based on TRC-LFSR structure
    ZHOU Bin;YE Yi-zheng;LI Zhao-lin;WU Xin-chun
    J4. 2009, 36(5):  945-950. 
    Abstract ( 1757 )   PDF (758KB) ( 1156 )   Save
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    Based on the twisting-ring counter (TRC) and linear feedback shift register (LFSR), a kind of test pattern generator, which can realizes two-dimensional test pattern compression is presented. The proposed approach utilizes the test set embedding technique based on TRC and LFSR reseeding schemes to achieve the vertical and horizontal compressions of the test set, which significantly reduces the width and length of the deterministic test set. Theoretical analysis shows that the length of LFSR of the design is reduced up to smax+2 from smax+20,  which increases the encoding efficiency. In order to target the minimization of the number of the LFSR seeds, an efficient LFSR seed selection algorithm is then proposed. Here, each LFSR seed is decoded as a TRC seed, and then, the TRC seed generates 2n2+n test patterns. Experimental results for the ISCAS89 benchmark circuits show that the proposed scheme requires 69% less test data storage compared with previous schemes, and that the test control logic is simple for all CUTs, and can be shared among multiple CUTs.

    Method for a linear array beam focusing in the near field based on amplitude weighting
    ZHONG Lan-xiang;LI Hong-hong;ZHANG Zhi-yong;SONG Yong-ming
    J4. 2009, 36(5):  951-956. 
    Abstract ( 1351 )   PDF (864KB) ( 1229 )   Save
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    Based on amplitude weighting, an approaching-to-function method for a linear array beam formed in the near field is proposed in order to reduce the complexity and cost of the phase shifter and controller in the phased array. By assuming that the amplitude distribution function in space to be δ(r-r<sub>0</sub>),  in which r<sub>0</sub> is the vector of focus, the value of every element radiation amplitude can be calculated. The validity of the method is also illustrated with examples. Moreover, this method can be extended to the planar array or other array elements with different polarization directions.