Table of Content

20 April 2012 Volume 39 Issue 2

  

Original Articles

Generation of optical single sideband with carrier signals using the  dual-parallel Mach-Zehnder modulator in the radio over fiber system

LIU Xiangling;HAN Kun;LI Jiandong;YUE Peng

J4. 2012, 39(2):  1-7.  doi:10.3969/j.issn.1001-2400.2012.02.001

Abstract ( 1721 )   PDF (1588KB) ( 1350 )   Save

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In the radio over fiber(RoF) system, the difference in power between optical carrier and optical sideband is large using the conventional optical single sideband with carrier(OSSB+C) modulation, resulting in lower receiver sensitivity. An improved method to generate OSSB+C signals is thus proposed based on the dual-parallel Mach-Zehnder modulator(MZM). By adjusting the direct current voltage of the MZM, the balanced power between the optical carrier and optical sideband is obtained for any modulation index, i.e., the value of the carrier-to-sideband ratio(CSR) is 0dB which is optimum. Simulation results show that the receiver sensitivity could be improved by as large as 7.8dB for the small modulation indexes, while about 0.7dB to 1.1dB for the medium and large modulation indexes. In addition, the influence of the drift of direct current bias voltage on the CSR and receiver sensitivity is also analyzed by simulation. The results show that if the bias drift is controlled within the range of 5％, the receiver sensitivity degrades a little, and the RoF system based on the proposed technique has the better robustness.

Application of quantum LDPC codes to quantum key distribution

XIAO Heling;CAI Ning;WANG Xiao

J4. 2012, 39(2):  8-11+23.  doi:10.3969/j.issn.1001-2400.2012.02.002

Abstract ( 1412 )   PDF (424KB) ( 1101 )   Save

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In this paper, the security of BB84 key distribution protocol is considered. We assume that in the protocol the eavesdropper Eve intercepts/resends photons transmitted between Alice and Bob with probability ε. First, the BB84 key distribution protocol will be made equivalent to a special Wire-tap channel model, where the main channel is a binary symmetric channel with probability of flipping bits 0.25ε and the eavesdropper's channel is a binary erasure channel with probability of erasure 1-ε. Using the coding method and properties of quantum LDPC codes CSS(C₁, C₂) for secure communication across the Wire-tap channel in the BB84 protocol is an equivalent proof of the security of BB84 protocol. Finally, the tolerable error rate of the BB84 protocol based on quantum LDPC codes can be obtained by calculating the secrecy capacity of this special Wire-tap channel.

Blind Rake receiver for TH-UWB systems with multi-user interference

KANG Xiaofei;YANG Jiawei;LIU Jian

J4. 2012, 39(2):  12-16+65.  doi:10.3969/j.issn.1001-2400.2012.02.003

Abstract ( 1122 )   PDF (571KB) ( 1033 )   Save

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A novel blind Rake receiver is proposed in order to suppress both multi-user interference (MUI) and inter symbol interference (ISI) for time-hopping ultra-wideband (TH-UWB) systems. The receiver firstly exploits the properties of the desired user time-hopping sequence to figure out a filter for eliminating partial MUI and ISI, and then uses the PASTd algorithm to estimate the channel and perform maximal ratio combining (MRC) to further improve the signal to interference plus noise ratio (SINR). Simulation results show that the proposed blind Rake receiver achieves a significant performance gain in comparison with the conventional receiver and Rake receiver, and can converge at the steady state rapidly. Furthermore, it requires less priori knowledge and has lower complexity.

Optimal power allocation of the DF cooperation system over  imperfect Nakagami-m fading channels

ZHANG Nan;GE Jianhua;GONG Fengkui;GAO Ming

J4. 2012, 39(2):  17-23.  doi:10.3969/j.issn.1001-2400.2012.02.004

Abstract ( 1237 )   PDF (618KB) ( 938 )   Save

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The impacts of power allocation under imperfect channel estimation on the symbol-error-rate (SER) are investigated for a cooperative network with multiple decode-and-forward (DF) relays over Nakagami-m fading. First,the approximate SER and asymptotic SER for M-QAM are provided by using the Theorem of Total Probability and the moment generating function (MGF). Then based on the presented compact asymptotic SER, the optimal power allocation is transformed to a typical convex optimization problem so that the optimal power allocation is reached to minimize the SER under the total power constraints. Simulations show that compared to the uniform allocation scheme, optimal power allocation scheme can significantly improve the performance of the cooperative system at the low to medium SNR, but can not improve the error floor at the high SNR under the imperfect channel estimation.

Novel low complexity LMMSE channel estimation algorithm

SHI Lei;GUO Baolong;LI Xiaoping;LV Liang

J4. 2012, 39(2):  24-28+50.  doi:10.3969/j.issn.1001-2400.2012.02.005

Abstract ( 1188 )   PDF (575KB) ( 1295 )   Save

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This paper presents a novel low complexity LMMSE channel estimation algrithom for the OFDM system to reduce computational complexity caused by matrix inverse operation in the MMSE estimator. Correlation bandwidth is used as a criterion to divide the large auto-correlation matrix into a number of sub-matrixs, including the non-overlap and overlap method. The diaglog sub-matrix blocks representing low-frequency important channel information in the channel autocorrelation matrix are preserved while the other sub-matrix blocks are ignored, thus reducing autocorrelation matrix inversion computational complexity. BER and MSE performance of the new algrithom is evaluated in the frequency selective flat fading channel with comparison to the LMMSE, SVD algorithm. Simulation results and complexity anaysis show that low complexity is obtained at the slight cost of performance degradation.

No-reference video quality assessment over  the IP network based on packet loss

LIU Hechao;CHANG Yilin;YUAN Hui;YANG Jiawei

J4. 2012, 39(2):  29-34.  doi:10.3969/j.issn.1001-2400.2012.02.006

Abstract ( 1280 )   PDF (659KB) ( 1255 )   Save

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A novel no-reference video quality assessment model is proposed in order to meet the real-time and low cost requirements of video quality assessment over IP networks. The temporal complexity is calculated without decoding, and the effect of different types of frame loss on video quality is considered. In the proposed model, both spatial and temporal error concealment artifacts of the human visual system (HVS) and frame types are taken into account. Video qualities could be assessed without delay by utilizing the proposed model. Experimental results show that the scores obtained by the proposed model highly agree with the subjective assessment scores. Compared with the video quality evaluation model in G.1070, an average performance gain of 6.96％ could be achieved by the proposed model in terms of relativity to subjective results.

Hybrid cooperation scheme for the AF-MIMO relaying system

LI Dong;SHI Haoshan;CHENG Wei

J4. 2012, 39(2):  35-39.  doi:10.3969/j.issn.1001-2400.2012.02.007

Abstract ( 1356 )   PDF (483KB) ( 1039 )   Save

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A hybrid relay selection scheme based on amplify-and-forward (AF) is proposed in the general cooperative communication network. In the proposed scheme, all the relays are divided into two groups, referred to as group P and group Q depending on whether they can perform decoding correctly or not. Both group P and group Q will select the relay which has the maximum signal-to-noise ratio at the destination. Simulation results show that the proposed relay selection scheme significantly outperforms the conventional AF selection scheme in terms of both bit error rate (BER) and channel capacity, and that these performance gains considerably grow as the transmission power of group P increases and antennas equipped on the nodes increases respectively.

Automatic generation algorithm for the neighbor cell list  based on the adaptive SINR threshold

ZHANG Wenzhu;HE Jiaxing

J4. 2012, 39(2):  40-44+137.  doi:10.3969/j.issn.1001-2400.2012.02.008

Abstract ( 1242 )   PDF (613KB) ( 1006 )   Save

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In the Long Term Evolution (LTE) system, to ensure the normal execution of communication, each cell must maintain a neighbor cell list which decides the scope and direction of a terminal’s switch. The traditional approach for configuring a neighbor cell list is carried out by a network engineer according to the site survey results, which not only consumes large amounts of time and manpower, but also can not present the statistical characteristic of the whole network. An automatic neighbor cell list generation algorithm based on the adaptive SINR threshold is proposed. The SINR threshold and “vote model” are introduced in this algorithm, which takes into full account the cell type in the LTE network, and effectively reflects the actual network environment. The algorithm ultimately realizes dynamic management of the neighbor cell list. Simulation results show that different SINR thresholds can affect the redundancy ratio and accuracy ratio of a neighbor cell list.

Spectrum allocation algorithm based joint rules  for the cognitive radio

LIU Yutao;JIANG Mengxiong;XU Cong;TAN Xuezhi

J4. 2012, 39(2):  45-50.  doi:10.3969/j.issn.1001-2400.2012.02.009

Abstract ( 1427 )   PDF (701KB) ( 991 )   Save

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The dynamic spectrum access technology can achieve near-optimal spectrum utilization by allowing cognitive users to sense and utilize available spectrum opportunistically. Aiming at the “phenomena of once-assignment aggregation” of the graph coloring algorithms, a novel joint rules algorithm based on the collaborative max sum bandwidth rule and collaborative max proportional fair rule is proposed. The algorithm uses two different rules when calculating the node label, through which the allocation fairness between the cognitive users is improved, and the time overhead is reduced at the same time. Simulation results verify the feasibility and validity of the proposed algorithm.

Performance analysis and optimal power allocation for the  incremental quadrature modulation cooperative system

SHI Xiaoye;GE Jianhua;LI Jing;HUANG Songtao;MA Bo

J4. 2012, 39(2):  51-58.  doi:10.3969/j.issn.1001-2400.2012.02.010

Abstract ( 4189 )   PDF (680KB) ( 940 )   Save

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In order to improve the reliability of the quadrature modulated (QM) cooperative diversity system, an incremental quadrature modulated (IQM) cooperative diversity system and its power allocation schemes are proposed, by introducing incremental relaying. Firstly, the system’s Markov states-transform probability is obtained through the analysis of the system's Markov-process and then the closed approximate solution of the frame error rate (FER) is acquired. Finally, a quasi-optimized power allocation schemes (QOPA) with low complexity is presented. By minimizing the frame error rate (FER), the optimal power factors are obtained through iterative computation. Simulation result shows that the IQM system outperforms the traditional QM system by a maximum SNR benefit of 4dB when the FER is in the range ［10^-4,10^-2］. Moreover, an additional 3dB performance gain is obtained by adopting the QOPA schemes.

Dynamic extended mim-sum decoding algorithm for  Q-ary LDPC codes

LIN Wei;BAI Baoming;WANG Xuepeng

J4. 2012, 39(2):  59-65.  doi:10.3969/j.issn.1001-2400.2012.02.011

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Decoded with the extended min-sum (EMS) algorithm, q-ary LDPC codes suffer great performance degradation compared with that decoded with the q-ary sum-product algorithm (QSPA) in case the length n_m of message vectors is too small. To solve this problem, a dynamic EMS (D-EMS) algorithm is proposed in this paper. First, we examined the distribution of likelihood values among GF(q) symbols in the message vectors, and concluded that the likelihood values would concentrate to a small portion of symbols as the iteration number increases. Therefore, the D-EMS algorithm first set the length of message vectors to n_m1, then truncate it to n_m2 after certain decoding iterations, thus the decoding computational complexity can be efficiently reduced. Meanwhile, in order to reduce the complexity of real comparisons in the decoder, the proposed algorithm employs the bubble check (BC) algorithm during the check node elementary steps. Complexity analysis and simulation results indicate that, under appropriate parameter configurations, while efficiently reducing the decoding complexity of the EMS algorithm, the D-EMS algorithm performs nearly as well as the corresponding EMS algorithm over both AWGN and Rayleigh fading channels, and thus can be efficiently applied to practical communication systems based on q-ary LDPC codes.

Attribute-based access control scheme for the perceptive layer  of the Internet of Things

REN Fang1;MA Jianfeng1,2;HAO Xuanwen1

J4. 2012, 39(2):  66-72.  doi:10.3969/j.issn.1001-2400.2012.02.012

Abstract ( 1666 )   PDF (623KB) ( 1527 )   Save

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In order to achieve the fine-grained access control and the anonymity of the user access to data in the Internet of Things, an attribute-based access control model is proposed and realized by using the bilinear map. In this scheme, users request data access to the sensor node based on their attributes certificates and the sensor node determines whether to allow access according to the threshold principle. This scheme effectively realizes the flexible fine-graind access control and anonymous access to data. The number of interactions between users and sensor nodes is minimized and the computation of sensor nodes is reduced to one public key encryption. Analysis shows that the scheme has the advantages over the current access control mechanisms of better scalability and lower cost in communication and computation and can adapt to access control requirement of perceptive layer of the Internet of Things.

Improved 3D fine granularity priority ordering method  for the scalable video bit stream

XIAO Song;LIU Ting;DU Jianchao;LU Ji

J4. 2012, 39(2):  73-79.  doi:10.3969/j.issn.1001-2400.2012.02.013

Abstract ( 1358 )   PDF (1414KB) ( 942 )   Save

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In order to reduce the effects of the network delay, bandwidth fluctuation and the packet loss and improve the quality of the reconstructed video, an improved 3D fine granularity priority ordering method for the scalable video bit stream is proposed. The method arranges the SVC coding layers according to their rate-distortion (RD) characteristics from spatial, temporal and SNR aspects within a group of picture (GOP), so that the optimal reconstructed video quality can be obtained when a certain number of packets are correctly received at the decoder. By layer refinement and improved iteration, the method overcomes the imprecision of the distortion calculation in the previous method when the variation of the layer bit stream is large, and provides finer granularity ordering characteristics for the layered bit stream. Simulation results show that the proposed method can effectively improve the reconstructed quality of SVC bit streams compared with existing methods.

New algorithm for reducing speckle noise in the SAR image

ZHU Lei;SHUI Penglang;WU Aijing

J4. 2012, 39(2):  80-86.  doi:10.3969/j.issn.1001-2400.2012.02.014

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To reduce speckle noise and preserve edge characteristics in synthetic aperture radar (SAR) images, an additive transform noise mode of speckle noise in the SAR image is given and a new algorithm for speckle reduction by the combination of self-snake diffusion and regulated L1-L2 optimization under undecimated wavelet packet transform (uWPT) is proposed. In the new method, a SAR image is first decomposed into multiple subbands by multi-level uWPT. The lowpass subband is filtered by self-snake diffusion, and the subband filtered is regarded as the local mean of the original SAR image in the wavelet domain. Based on the local mean, the adaptive and shrinkage soft-thresholding filter is applied to the remaining subbands by regulated L1-L2 optimization. Finally, the despeckled image is recovered from all of filtered subbands by the inverse uWPT. Experimental results show that compared with the Kuan filter algorithm, the P-M diffusion filter algorithm and the Γ-WMAP algorithm using undecimated wavelet transform, the proposed algorithm has better performance in terms of reducing speckle noise and preserving the edge of SAR images.

Improved isoperimetric algorithm for image segmentation

WANG Yunfei;BI Duyan;HUANG Fei

J4. 2012, 39(2):  87-94+212.  doi:10.3969/j.issn.1001-2400.2012.02.015

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An in-depth analysis is conducted on the graph-theory-based-isoperimetric-partition-algorithm (GTBIPA), which has such drawbacks as low noise immunity and low iterative efficiency when applied to image processing, and a new approach is presented. In this new approach, the intensity of arbitrary nodes in graph are analogized as the length and width of a rectangle. On the condition of a constant perimeter of a rectangle, a new weighting function is designed by using the ratio between the present and the maximum area of the rectangle, so that the normalized problem is directly avoided; and by the participation of suboptimal isoperimetric ratio in iterative partitioning, the iteration efficiency of the algorithm is improved. Experimental results show that this new algorithm can efficiently enhance the performance of the GTBIPA by improving its noise immunity and reducing the number of iterations by 10%~30％.

Offset cancellation preamplifier for pipelined folding A/D converter

LI Xiaojuan;YANG Yintang

J4. 2012, 39(2):  95-100+174.  doi:10.3969/j.issn.1001-2400.2012.02.016

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This paper presents an offset cancellation preamplifier based on the requirement of the pipelined folding A/D converter. The offset storage technique is realized with switched capacitor circuits to eliminate the effect of the input offset voltage on the resolution. The neutralization technique is introduced by MOS capacitors to reduce the kickback noise. In the SMIC 0.18μm CMOS process, by Mente Carlo simulation the preamplifier with offset variance of 3.24mV is verified and 362μW is consumed at 1.8V and 200MHz. The measured peak INL and DNL are 1.6LSB and 0.6LSB for the 10bit 100MS/s A/D converter. SFDR is 55dB when f_in=32MHz at f_s=100MHz.

Novel method for compensation of timing mismatch in  time-interleaved ADC

WANG Yajun;LI Ming

J4. 2012, 39(2):  101-107.  doi:10.3969/j.issn.1001-2400.2012.02.017

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A novel method to compensate the timing mismatch in time-interleaved ADCs (TIADC) in the digital domain is presented. Based on the principle of timing mismatch, the variable digital fractional delay element is used to compensate the mismatch in the new method, and a good performance is achieved. Compared with existing algorithms, this new method is very easy in conception and has major advantages from an implementation point of view. It is simple and efficient to implement and extend. A farrow structure is adopted to separate error parameters, so this method could easily be combined with the estimation method to build an adaptive system. Simulation results indicate that the proposed method can lead to an improvement of more than 30dB in the signal-to-noise-and-distortion ratio (SINAD) of TIADC. And the new method is not sensitive to additive noise of input.

Optimization of zero-crossing distortion in the CRM PFC converter  with one cycle control

LI Yani;YANG Yintang;ZHU Zhangming;QIANG Wei;LIU Lianxi

J4. 2012, 39(2):  108-113.  doi:10.3969/j.issn.1001-2400.2012.02.018

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To reduce the total harmonic distortion (THD) and increase power efficiency, based on a critical conduction mode (CRM) power factor correction (PFC) converter with one cycle control, the optimization of the zero-crossing distortion is discussed. The introduced periodic self-starting timer could provide a trigger signal to open a new cycle no matter whether the inductor current decreases to zero, thus avoiding the conduction delay produced by the reverse leakage current of the inductor with less zero-crossing distortion and THD. An adjustable shunt resistor connected between the auxiliary winding and the oscillator could regulate the output signal slope of the oscillator to control the PWM turn-off time by monitoring the inductor current of the auxiliary winding real time. It could effectively reduce the current distortion in the vicinity of the input voltage zero-crossing points. The higher the frequency of ac input line voltage, the better the optimization. At 50Hz 220V_AC, the input current is 120mA, the output power is 36W, the experimental THD of improved PFC converter is only 3.8％, the power factor is 0.988, the load adjust rate is 3％, the linear adjust rate is less than 1％, and the efficiency is 97.3％. Both theoretical and practical results reveal that the zero-crossing distortion and THD are reduced efficiently after optimization, especially when the ac line voltage is close to zero. The active die area is 1.61mm×1.52mm.

Artificial bee colony based low-energy consumption  high-performance mapping in NoC

DENG Zhi;GU Huaxi;YANG Yintang;ZENG Daibing

J4. 2012, 39(2):  114-119.  doi:10.3969/j.issn.1001-2400.2012.02.019

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In order to overcome the hotspot problem in the center of the mesh network and high energy consumption, an Artificial Bee Colony(ABC) based mapping algorithm is proposed to solve the low-energy consumption high-performance mapping mode, which is set up by the analysis of the Network-on-Chip(NoC) architecture. The algorithm can lead to a low energy consumption and balanced traffic optimal mapping set by simulating the operations of different bees. The result can be achieved by selecting the optimal mapping from the intersection of the solution set. Simulation results show that the proposed mapping not only accomplishes the mapping from the IP core to node at a fast rate, but also has better performance in energy consumption, latency and traffic balance.

Method for angle estimation of coherent sources  in bistatic MIMO radar

FU Weibo;SU Tao;ZHAO Yongbo;HE Xuehui;ZHAO Guanghui

J4. 2012, 39(2):  120-126+185.  doi:10.3969/j.issn.1001-2400.2012.02.020

Abstract ( 1348 )   PDF (678KB) ( 908 )   Save

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Aiming at the angle estimation for coherent sources in bistatic MIMO radar, two methods based on the dimension reduction DOA matrix are presented in spatially white noise and in spatially colored noise, respectively. Firstly, the virtual array data of multi-target echoes in MIMO receivers is uncorrelated. Secondly, DOA matrices in different noise environments are constructed. The dimension reduction DOA matrices which reduce the computational complex are obtained by the relationship between signal subspace and DOA matrices. Finally, the joint estimation of DOD and DOA can be obtained by the corresponding relationships between the eigenvalue or eigenvector and the estimated parameters. The proposed methods do not need the multi-dimensional peak search, and can estimate the parameters of coherent sources without pairing in both two noise circumstances. Moreover, it is applicable to receiving arrays without an invariance structure. Numerical results are presented to demonstrate the effectiveness of the method advanced.

Research on recognizing the radar signal using  the bispectrum cascade feature

WANG Shiqiang;ZHANG Dengfu;BI Duyan;XUE Deyou;YONG Xiaoju

J4. 2012, 39(2):  127-132+191.  doi:10.3969/j.issn.1001-2400.2012.02.021

Abstract ( 1461 )   PDF (547KB) ( 996 )   Save

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To deal with the problem of emitter identification caused by parameter complexity and agility of multi-function radars, a new identification method based on the bispectrum feature is proposed. This method takes the bispectrum of emitters as the specific emitter feature and the Bhattacharyya distance measurement as the cascade feature extraction algorithm. Bispectrum analysis can restrain the effect of Gauss White Noise on radar signal, and retain the amplitude and phase information. So this paper utilizes this characteristic to enhance the validity of the radar emitter signal feature. Aimed at the problem that the signal bispectrum contains many redundancy bispectrums, the Bhattacharyya distance is introduced to extract the bispectrum cascade feature with best separation as the radar signal feature. Experimental results show that the proposed method is suitable for extracting radar signal characteristics and has a good recognition performance. The average accuracy is not less than 95％ at the signal to noise ratio of a wide range.

Analysis of the electrical large scattering problem using  the pre-corrected multilevel fast multipole algorithm

MAN Mingyuan;LEI Zhenya;XIE Yongjun;WANG Yuanyuan

J4. 2012, 39(2):  133-137.  doi:10.3969/j.issn.1001-2400.2012.02.022

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In order to accelerate the solution procedure of scattering problems with the multilevel fast multipole algorithm, a pre-corrected method is presented. Using the Physical Optics method(PO), the PO currents could be obtained as pre-corrected currents. A rather sparse impedance matrix is generated to evaluate the PO surface current. Because the difference between unknown and PO currents is closer to the zero vectors than the unknown currents themselves, it does need less iteration steps using the difference as the unknown vector to get the solution. Numerical results demonstrate that the method could decrease the number of iterations and greatly reduce the time of solution with consistent precision.

Modified MUSIC algorithm for improving the resolution  of 2-D direction of arrival estimation

SI Weijian;LAN Xiaoyu;LIU Xue

J4. 2012, 39(2):  138-144.  doi:10.3969/j.issn.1001-2400.2012.02.023

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The resolution of the classical two-dimensional (2-D) Multiple Signal Classification(MUSIC) algorithm is limited by the certain array aperture under the contexts of low signal to noise ratio(SNR) and finite snapshots. Focusing on this problem, a modified 2-D direction of arrival (DOA) method based on the MUSIC algorithm is proposed. By calculating the second partial differentiation for the azimuth and elevation of the MUSIC spectrum, some negative peaks are shown around the original DOAs while MUISC spectrum does not make peaks there. The performance of the proposed method is evaluated for separating closely spaced sources in difficult contexts, for instance, a low SNR and a small number of snapshots in comparison with 2-D MUSIC method through computer simulations. Furthermore, the new approach is suitable to any array shape.

Green IP lookup architecture and algorithm based on  the parallel multi-pipeline

YUAN Bo;WANG Binqiang;WANG Zhiming

J4. 2012, 39(2):  145-152+167.  doi:10.3969/j.issn.1001-2400.2012.02.024

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With the development of the next generation internet, the existing router architecture faces many problems,such as performance,complexity and power consumption. With the increase of the network size, how to implement a low-power MSF for IP lookup is a challenge in green and high-performance router designing. This paper represents an FIB multi-level mapping parallel multi-pipeline routing lookup architecture(FMML), with a dynamic routing table mapping algorithm designed to determine the optimal strides for building tree bitmap tries. Finally, experiments using real-life routing tables demonstrate that our solution can reduce 30％ power consumption of routing lookup.

Influence of thermal contact conductance on the side-face of  the crystal rod on wavefront distortion in the solid-state laser

LIU Haiqiang;GUO Zhen;WANG Shiyu;LIN Lin;JIN Wenlong;LI Bingbin;CAI Defang

J4. 2012, 39(2):  153-158.  doi:10.3969/j.issn.1001-2400.2012.02.025

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For the LD end-pumped solid-state laser working with round-rod material, the crystal rod is held and cooled by the metal heat sinks. The non-axisymmetric assembly pressure on the side-face of the crystal rod makes the thermal contact conductance between the crystal and the heat-sink non-axisymmetric, which affects the spatial distribution of the temperature inside the crystal rod and the spatial distribution of wavefront. Based on the truncated-Gaussian model and the plastic-deformation model, the model of the thermal contact conductance is established. For the Gaussian heat consumption, the changes of the end-face temperature of the crystal and the wavefront distortion with the radius and the direction angle under different assembly forces are obtained, and the results are compared with those of the case when using the indium foil as thermal interface material. The results show that in the case of the same radius the end-face temperature and the wavefront distortion reach the minimum in the direction of bottom of the heat-sink groove, and reach the maximum in the direction of the contact area of the heat-sink couple. With the increasing assembly force, the end-face temperature reduces overall, and the wavefront distortion gets more uniform. With the indium foil as thermal interface material, the end-face temperature and the wavefront distortion decrease overall. And the the spatial distribution of the temperature of the crystal rod and the wavefront distortion is axisymmetric.

Array antenna pattern synthesis based on the  implicit space mapping algorithm

WANG Wentao;WANG Fuwei;GONG Shuxi;WANG Xing

J4. 2012, 39(2):  159-163+199.  doi:10.3969/j.issn.1001-2400.2012.02.026

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The implicit space mapping(ISM) algorithm and the method of moments(MoM) are combined to achieve the array pattern synthesis and improve the optimization efficiency. In the process of optimization, the MoM models with simple and complex mesh subdivision are used as the ISM coarse model and fine model, respectively. The feed amplitude or phase is selected as the auxiliary parameter and the differential evolution(DE) algorithm is used in the process of parameter extraction to achieve the approximation from coarse model to fine model. Finally, three optimization examples for amplitude, phase, and element spacing are presented. The results show that the implicit space mapping algorithm can effectively improve the optimization speed and complete the pattern synthesis.

Investigation of the influence of deposition temperature on  ALD deposite HfO₂ high k gate material

KUANG Qianwei;LIU Hongxia;FAN Jiwu;MA Fei;ZHANG Yanlei

J4. 2012, 39(2):  164-167.  doi:10.3969/j.issn.1001-2400.2012.02.027

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HfO₂ high k dielectric films are deposited on Si(100) by the atomic layer deposition technique at different temperatures, and the influences of deposition temperature on the characteristic of HfO₂ are investigated. Experimental results show that the deposition rate of HfO₂ is seriously influenced by the deposition temperature, which will be rapidly increased with the increased deposition temperature in the high temperature region or the decreased temperature in the low temperature region. By analyzing the C-V characteristic of HfO₂, it is found that both the dielectric constant and the quantity of oxide defects of HfO₂ deposited at different temperatures change greatly, and HfO₂ deposited at the temperature of 280-310℃ has the least oxide defects.

High-speed gate driver with a simple structure for power MOSFET

HE Huisen;LAI Xinquan;XU Wendan;ZHAO Yongrui;TIAN Lei;DU Hanxiao

J4. 2012, 39(2):  168-174.  doi:10.3969/j.issn.1001-2400.2012.02.028

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A novel gate driver with a low transmission delay and ultra-low dead-time is proposed for driving power MOSFET. It controls the charge time and discharge time of the gate capacitor for minimizing dead-time, and no extra current bias and logic circuits are required, so it can simplify the driver circuit and reduce the noise in the current bias. Based on the 0.4 μm BCD process, the simulation is done in the Cadence environment, with good performance observed where the dead-time is below 10ns and the transmission delay is below 70ns. Then a Power Factor Correction (PFC) IC which utilizes this gate driver is tested for validation, and the test results indicate that the t_rise and t_{f_all} are 90ns and 55ns respectively that the power factor is 0.995, and that the Total Harmonic Distortion (THD) is as low as 6.5％.

Kernel k-means clustering algorithm for detecting communities  in complex networks based on eigenvector

FU Lidong;GAO Lin

J4. 2012, 39(2):  175-180.  doi:10.3969/j.issn.1001-2400.2012.02.029

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To detect the community structure in weighted complex networks, the modularity density function D is generalized to weighted variants(WD) and shows how optimizing the weighted function WD can be formulated as a spectral clustering problem, and a weighted kernel k-means clustering problem. We also prove the equivalence of both clustering approaches based on WD in mathematics. Using the equivalence, we propose a new eigenvector-based kernel clustering algorithm to detect communities in complex networks. Experimental results indicate that it has better performance compared with either the direct kernel k-means algorithm or direct spectral clustering algorithm in terms of quality.

Crest factor over-current protection circuit in the electronic ballast

SHI Lingfeng;CAO Chengmei;REN Juanli;KANG Hui

J4. 2012, 39(2):  181-185.  doi:10.3969/j.issn.1001-2400.2012.02.030

Abstract ( 1158 )   PDF (486KB) ( 987 )   Save

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A crest factor over-current protection circuit is presented. The resistance of the low-side drive tube is used to realize resonant inductor current sampling and  crest factor measurement is taken to obtain over-current protection. The circuit is completed on over-current protection for different resonant inductors, so that it extends the work time of electronic ballasts. Typically in the 0.5μm BCD(Bipolar, CMOS, DMOS) process, Hspice simulation results show that the designed circuit can accurately realize over-current protection for the resonant inductor.

Application of empirical mode decomposition and  wavelet transform in structural modal parameter identification

XU Yalan;MA Juan;CHEN Jianjun;LIU Zhen

J4. 2012, 39(2):  186-191.  doi:10.3969/j.issn.1001-2400.2012.02.031

Abstract ( 1375 )   PDF (1478KB) ( 1100 )   Save

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To overcome the limitation of hilbert-huang transform in decoupling the structural modes in vibration signal processing, a novel structural modal parameter identification method is proposed by combining empirical mode decomposition(EMD) with Morlet wavelet transform. First, the dynamical response signal is decomposed by using the EMD method to achieve intrinsic mode functions and implement the sifting processing of modes, on the basis of which the signal is reconstructed. Then, the variation of the transient amplitude and phase of wavelet transform coefficients with time is given by using the Morlet wavelet and the least squares fit, on the basis of which corresponding modal frequencies and modal damping ratios and mode shapes are achieved. Simulation results show that the method is effective in modal decoupling and accurate in modal parameter identification, which can not be implemented effectively by using the Hilbert transform of the individual intrinsic mode function due to modal mixture.

Equalization of inductively coupled connector

QU Yongzhe;LI Yushan;YAN Xu;DING Tonghao;JIANG Dongchu

J4. 2012, 39(2):  192-199.  doi:10.3969/j.issn.1001-2400.2012.02.032

Abstract ( 1321 )   PDF (1979KB) ( 976 )   Save

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The inductively coupled connector can be used for high-speed digital signal transmission of board-level interconnect. With the increasing signal transmission rate or transformer inductance, the receiver-side of the inductively coupled connector will suffer excessive inter-symbol interference, and can not effectively recover the signal. To solve this problem, the ALTERA driver-side equalization scheme is proposed by analysing the reasons of inter-symbol interference and the equalization ratio calculation method of this scheme is also given. The equalization scheme is implemented through selection of an appropriate equalization ratio to increase high frequency components of the signal and reduce the low frequency components of the signal at the driver-side to reduce the inter-symbol interference and improve pulse magnitude, and the signal can be recovered with a simple low power trigger circuit. Simulation results show that using the driver-side equalization scheme can effectively eliminate inter-symbol interference, and that the choice of inductance and the signal transmission data rate are independent of each other, so the larger inductance of transformer can transmit high-speed digital signals.

Synthesis rules of WF-nets and their application in process design

ZHANG Man;DUAN Zhenhua

J4. 2012, 39(2):  200-206.  doi:10.3969/j.issn.1001-2400.2012.02.033

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In view of the limitation of one node extension in the node refinement method during the workflow net (WF-net) modeling, a WF-net refinement method based on Petri net synthesis rules is proposed. The synthesis rules of live and bounded free choice nets are added with constraints to adapt them to the refinement of free choice WF-nets. Then separable WF-nets are defined and their separability-preserving synthesis rules are given. It is proved that the synthesized WF-nets by these rules from free choice or separable WF-nets are sound. For the two classes of WF-nets, this method enables their refinement to involve more than one node, and provides their modeling with fine-grained guidelines of a different dimension.

Influence of the space-time coupling term on STAP

LV Wei;WANG Zhijie;LI Jianchen;WANG Mingzhou;YANG Baomin;HU Qiao

J4. 2012, 39(2):  207-212.  doi:10.3969/j.issn.1001-2400.2012.02.034

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In order to use the power spectrum propagation characteristics and adopt the theory of STAP for reverberation suppression and moving object detection, an improved method of STAP for sonar is proposed. Firstly, the principle of STAP is analyzed according to the echo model of radar. Secondly, comparing the echo models of sonar and radar, this method of STAP is presented and the Space-time coupling steering vector is used in space time processing. Finally, the proposed method of STAP is applied in space time processing and object detection. Simulation results illustrate that the modified method of STAP is beneficial to underwater object detection, and that applying the space-time coupling steering vector can increase the accuracy of the direction estimation of targets.