Table of Content

20 February 2014 Volume 41 Issue 1

  

Original Articles

Performance analysis of the polarization-space-time adaptive processing

DU Wentao;LIAO Guisheng;YANG Zhiwei

J4. 2014, 41(1):  1-5.  doi:10.3969/j.issn.1001-2400.2014.01.001

Abstract ( 914 )   PDF (613KB) ( 906 )   Save

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By the utilization of the additional polarized information, the minimum detectable velocity could be improved for space time adaptive processing under the polarimetric radar system. In this paper, the performance of polarization space time adaptive processing is analyzed and compared with the traditional space-time adaptive processing based on the output signal to clutter plus noise ratio, and the primary affecting factors of three dimensional processing are indicated. A preliminary result against an airborne simulation data verifies the conclusion.

Monte Carlo mobile node localization for NLOS environment

KUO Yonghong;ZHOU Wenwen;CHEN Jian

J4. 2014, 41(1):  6-12.  doi:10.3969/j.issn.1001-2400.2014.01.002

Abstract ( 1033 )   PDF (767KB) ( 701 )   Save

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Enhanced Monte Carlo Boxed (EMCB), based on the broadcasting messages of one-hop neighbor nodes, is proposed  in a mobile wireless sensor network for NLOS environment. The utilization efficiency of nodes is improved in the way of message flooding. The located nodes are used as the virtual anchor nodes in order to improve the location precision in the network with few anchors, optimizing the sample boxes of the neighbor nodes. Besides, both the theoretical limit of connectivity and the previous location information are used to enhance the filtering performance. Taking advantage of the one-hop messages, all the nodes are located layer-by-layer. Finally, the results of simulation show that the location precision is improved compared with the traditional algorithms in any situation. Especially, a good performance is achieved with fewer anchor nodes.

Temporal profile algorithm based on comparison filtering for detection of the infrared dim small target

DONG Weike;ZHANG Jianqi;SHAO Xiaopeng;LIU Delian

J4. 2014, 41(1):  13-17.  doi:10.3969/j.issn.1001-2400.2014.01.003

Abstract ( 1044 )   PDF (1935KB) ( 677 )   Save

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The detection performance of the traditional temporal profile algorithm deteriolates when the dim small target has a velocity correspmding to equivalent that of cloud edge clutters. This paper proposes a temporal profile algorithm based on comparison filtering as a responding method to the fake-alarm occurrence existing in the traditional detection algorithm. Based on the analysis of the time domain characteristics of the dim small target, cloud edge clutters as well as the stationary background, the characteristic of the temporal profile is adopted to restrain the stationary background, and then the spatial domain comparison filter is structured based on the fact that the pixels of the cloud edge clutters are continuous in spatial domain while the pixels of the dim small target are discrete, and the images after removal of the static background are filtered by the comparison filter; lastly, the connecting line of the stagnation points (CLSP) based filtering is used to realize the detection of the dim small target. Simulation data show that this algorithm can significantly eliminate the fake-alarm caused by the cloud edge clutters with an equivalent velocity of the target, thus further improving the detection probability of the dim small target.

Gaming network selection scheme considering performance-price ratio maximization in heterogeneous wireless networks

SONG Jianfeng;LI Jiandong

J4. 2014, 41(1):  18-22.  doi:10.3969/j.issn.1001-2400.2014.01.004

Abstract ( 903 )   PDF (562KB) ( 711 )   Save

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A heterogeneous network selection scheme based on game theory is proposed. A non-cooperation game model is formed which is aimed to maximize the overall profits of heterogeneous networks according to the integrated quality of service and the pricing scheme of each network. The network selection scheme is proposed to maximize the result of the quality of service versus price by means of Nash Equilibrium of the game. Analysis and simulation results validate the advantage of the scheme.

Joint pilot and iterative decoding carrier synchronization for the short burst transmission system

SUN Jinhua;WANG Xuemei;WU Xiaojun

J4. 2014, 41(1):  23-28+63.  doi:10.3969/j.issn.1001-2400.2014.01.005

Abstract ( 951 )   PDF (700KB) ( 736 )   Save

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Considering the low estimation accuracy and small synchronization range of carrier synchronization algorithms in low signal to noise ratio (SNR) for short burst communication systems, a joint pilot and iterative decoding soft-output carrier synchronization algorithm is proposed. Firstly, the received pilot sequence is extracted and modulation is removed, with the modulation-removed signals made cross-correlated. Then the summation of all the correlation values is used to perform initial carrier parameters estimation. Secondly, the pilot sequence is reused with the soft-output information based on the extended Turbo decoder to obtain fine frequency and phase estimation values. Theoretical analysis and simulation results show that the coarse estimation algorithm can satisfy the requirements of the frequency estimation range and estimation accuracy, and preamble-middle pilot placement is optimal for a certain length of the data frame; The turbo decoder can obtain more reliable soft-output information with small residual frequency offset after initial coarse synchronization when the normalized frequency offset is less than 1.5×10^-3, with the joint pilot and soft-output of the decoder used to estimate fine carrier parameters, which can make the turbo code achieve optimal BER performance.

Application of the invasive weed optimization algorithm to the pattern synthesis of array antennas

LIU Yan;JIAO Yongchang;ZHANG Yaming;WANG Xinkuan

J4. 2014, 41(1):  29-33+86.  doi:10.3969/j.issn.1001-2400.2014.01.006

Abstract ( 1058 )   PDF (751KB) ( 798 )   Save

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For overcoming the problem of slow convergence speed and local optimum by using the existing intelligent optimization algorithms in the pattern synthesis of antenna arrays with nulls, notches and sidelobe reduction, a novel invasive weed optimization(IWO) algorithm is presented, and an adaptive IWO is designed to improve the convergence speed and make a balance between the global and local searching ability. Simulation results show that, compared with other existing algorithms, the proposed algorithm performs better, with higher convergence speed and better computation accuracy.

Effective capacity analysis of MIMO beamforming

GUO Xiaobo;MO Daihui;WANG Lifeng;YI Kechu

J4. 2014, 41(1):  34-37.  doi:10.3969/j.issn.1001-2400.2014.01.007

Abstract ( 777 )   PDF (438KB) ( 711 )   Save

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Effective capacity describes the rate upper bound of the communication system under the quality of service(QoS) limitation. While the foregoing performance analysis focuses mainly on the single input single output and multiple input single output systems, this paper considers the effective capacity of the multiple input multiple output(MIMO) beamforming scheme. Given that the modulation(M-QAM or M-PSK) is restricted, we investigate the representative transmission scheme of MIMO beamforming: maximal ratio combining transmission, for which the closed-form formula of effective capacity is derived. Simulation results not only demonstrate the effectiveness of our performance analysis, but also show the relationship between effective capacity and average signal-to-noise ratio as well as the relationship between effective capacity and QoS parameter for various antenna configurations.

Analysis of the characteristics of squint circular scanning SAR and its imaging method

LIAO Yi;YANG Zemin;XING Mengdao;BAO Zheng;BAO Min

J4. 2014, 41(1):  38-44+74.  doi:10.3969/j.issn.1001-2400.2014.01.008

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Circular scanning SAR(CSSAR) is a new mode for fast large area SAR imaging by increasing the azimuth scanning speed. The squint CSSAR possesses the advantages that the side-looking CSSAR does not have due to its unique observing direction. However, the available signal characteristic analysis and imaging method for side-looking CSSAR become questionable when applied to the squint CSSAR. This paper establishes the echo range model and analyzes several parameters such as azimuth scanning speed, Doppler characteristics and azimuth resolution according to the moving feature of squint CSSAR. Furthermore, the internal relationship between the squint CSSAR and the classical stripmap mode is revealed. The range approximation model as well as the corresponding imaging method is analyzed. Computer simulation results validate the conclusions and the imaging method.

Method for sparse component analysis in the shearlet domain

JI Jian;LI Xiao

J4. 2014, 41(1):  45-52+146.  doi:10.3969/j.issn.1001-2400.2014.01.009

Abstract ( 916 )   PDF (10518KB) ( 709 )   Save

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In applications of the image blind source separation, the traditional method of Independent Component Analysis(ICA) computes the mixed matrix by using source image directly, without using the prior knowledge that images can be represented sparsely in the transform domain, and it can not lead to a better effect. Based on the capacity of image sparse representation by shearlet, a method of sparse component analysis in the shearlet domain is presented. The image mixed source is first transformed to the shearlet domain and obtains a shearlet coefficient, then the sparsest coefficient is selected by computing kurtosis, and finally the sparse coefficient is used as the input of the ICA method to realize image separation. The complexity of the solving procedure represents a significant decrease since it chooses a less sparse coefficient. Experimental results show that, compared with the traditional ICA method, the method in this paper leads to a better separation effect and shortens the operation time of the algorithm.

Novel dual-mode square loop microstrip bandpass filter

SUN Shoujia;WU Bian;LIANG Changhong

J4. 2014, 41(1):  53-56.  doi:10.3969/j.issn.1001-2400.2014.01.010

Abstract ( 1044 )   PDF (1079KB) ( 741 )   Save

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This paper presents a novel dual-mode square loop resonator with a compact size. Firstly, the odd-even-mode method is utilized to analyze the resonant property of the proposed resonator since its structure is symmetrical, and the passband center frequency can be easily tuned by changing the lengths of a pair of loaded open-ended stubs. Secondly, source-load coupling is introduced to produce a new transmission zero and improve the passband selectivity. Finally, a microstrip dual-mode bandpass filter (BPF) centering at 1.95GHz with a 3dB fractional bandwidth (FBW) of 37.7％ is designed and fabricated. The measured and simulated results in good agreement are presented.

Adaptive waveform selection approach for target tracking

JIN Biao;JIU Bo;LIU Hongwei;SU Tao

J4. 2014, 41(1):  57-63.  doi:10.3969/j.issn.1001-2400.2014.01.011

Abstract ( 1175 )   PDF (704KB) ( 708 )   Save

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Within an adaptive interacting multiple model (IMM) framework, an approach to selecting the transmitted waveform of radar is proposed. The adaptive IMM algorithm is attained when the constant-velocity (CV) model and the current statistical model are applied to the IMM filter. Firstly, the error ellipse orthogonal method is derived from information theory, and an equivalent form is given in terms of control theory. According to the equivalent form, the range and velocity tracking error can not be adjusted effectively using the error ellipse orthogonal method. To solve this problem, an adaptive transmitted waveform selection approach is proposed based on the minimum mean-squared error, combining with the adaptive IMM algorithm. Simulations show that the proposed algorithm is feasible and effective.

Feature quantitative model and performance analysis of infrared imaging under strong radiation source disturbance

GUO Bingtao;WANG Xiaorui;JIN Weiguo;WANG Xiaobing;HUANG Xiaomin

J4. 2014, 41(1):  64-68.  doi:10.3969/j.issn.1001-2400.2014.01.012

Abstract ( 1060 )   PDF (559KB) ( 705 )   Save

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The strong radiation source(such as battlefield fire) has become an important factor affecting the infrared imaging quality. First, a feature quantitative model of infrared imaging under strong radiation source disturbance is built based on the imaging signal conversion mechanism and by simultaneously considering the signal response characteristic,dynamic range, automatic gain characteristic(AGC) and gray level quantization and display. Then, a simulation of the output image of the infrared imaging system is performed on the basis of the model mentioned above and the simulation platform developed in our laboratory. Finally, a quantitative analysis of the relationship between the energy of the strong radiation source and the brightness(contrast) of the system's output image is made. The results will be used for providing a theoretical basis and technical support for the research on the infrared imaging system anti-interference ability protection in the battled environment.

Autofocusing the synthetic aperture radar imagery by the fast back-projection algorithm

ZHANG Lei;LI Haolin;XING Mengdao;BAO Zheng

J4. 2014, 41(1):  69-74.  doi:10.3969/j.issn.1001-2400.2014.01.013

Abstract ( 1067 )   PDF (3171KB) ( 733 )   Save

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Time-domain Fast Back-Projection (FBP) is an accurate and efficient solver to generate high-resolution Synthetic Aperture Radar(SAR) images. However, motion errors seriously degrade the performance of the FBP image when the accuracy of the position system does not reach the wavelength level. In this paper, we propose a novel multi-aperture map drift (MAMD) algorithm, which is implemented within the FBP iterations. The autofocus processing is realized by estimating the shift of sub-aperture images and it keeps the high accuracy of the FBP algorithm. Experiments by using real airborne SAR data validate the effectiveness of the proposed algorithm.

Method for transforming cyclic circuits into acyclic equivalents

DI Zhixiong;SHI Jiangyi;MA Peijun;ZHANG Yi;YUAN Li;HAO Yue;XU Zhao

J4. 2014, 41(1):  75-80.  doi:10.3969/j.issn.1001-2400.2014.01.014

Abstract ( 1295 )   PDF (557KB) ( 719 )   Save

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The cyclic circuit is capable of reducing the area and power consumption, but it is difficult for tools such as static timing analyzers to analyze and compute. Furthermore, the simulation and DFT for the cyclic circuit are more expensive and complicated. Thus, a method for transforming cyclic circuits into acyclic equivalents based on the SAT(Boolean Satisfiability) is presented in this paper in order to remove the unwanted cycles in the high-level synthesis process. Different from the available researches, the SAT and static logic implication are introduced in this paper. Meanwhile, by analyzing the structure and mechanism of the cyclic circuits, some novel rules are presented to obtain the acyclic equivalents more precisely and effectively. Experiments are performed in our scientific research projects and the IPs which come from Opencore. And the transforming time and the area are decreased by 28％ and 16％.

Differential co-localization method using the X-ray pulsar

FENG Dajun;XU Luping;SONG Shibin;TIAN Xi

J4. 2014, 41(1):  81-86.  doi:10.3969/j.issn.1001-2400.2014.01.015

Abstract ( 1457 )   PDF (700KB) ( 644 )   Save

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Relative navigation traditionally using inter-satellite links demands higher inter-satellite time synchronization, and has no ability of absolute positioning and timing. In this paper, we propose a relative navigation model of X-ray pulsar-based co-localization. The main satellite receives the radiation pulse signal from X-ray pulsars, and sends the arrival time and individual pulse's feature to adjacent satellites through inter-satellite links. Then by detecting the inter-satellite time difference of X-ray pulsar signals we can establish the location equation to find the inter-satellite relative position. We deduce the error correction equation of the pulse TOA prediction model and analyze the identifiability of individual pulses of the pulsar. The method proposed in this paper is less influenced by the TOA prediction model, ephemeris error, etc. It is helpful for achieving on-line self-adaption correction of the TOA prediction model and combined orbit determination of satellite constellation.

Fast frequency sweep analysis for antennas mounted on platforms using the wire-surface model

Lü Zhengliang;GONG Shuxi;ZHANG Pengfei;ZHAO Bo;WANG Fuwei

J4. 2014, 41(1):  87-91.  doi:10.3969/j.issn.1001-2400.2014.01.016

Abstract ( 1188 )   PDF (1414KB) ( 648 )   Save

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The best uniform rational approximation in conjugation with the method of moments (MoM) is applied to analyze the wide-band electromagnetic characteristic of the wire-surface objects. For the analysis of wire-surface objects, all the wire-surface models are substituted by surface-surface models, and then the radiation problem can be solved more efficiently by the Chebyshev approximation for the surface current combined with discrete wavelet transform (DWT). This technique offers a considerable computational saving in terms of memory. To improve the accuracy, the polynomial series is replaced by the Maehly series and the best uniform rational approximation is obtained. Numerical examples are performed to demonstrate the validity.

Mechanism analysis and physical process of bipolar junction transistor failure due to HPM injection from the base

FAN Juping;YOU Hailong;JIA Xinzhang

J4. 2014, 41(1):  92-97.  doi:10.3969/j.issn.1001-2400.2014.01.017

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In order to determine the influence of HPM on BJT, the physical process and model are proposed based on the experimental phenomena of BJT injecting HPM from the base. Simulation results by using the model and process proposed in the paper show that the main mechanism of failure and degradation of BJT caused by HPM is that the induced voltage pulse generated by HPM leads to the burn-up and the formation of the fuse element and defect in the base. The burnt area and the number of defects which vary with the power and time of HPM on the devices cause the device failure and the change of DC characteristics.The simulation result is in good agreement with the phenomena of the BJT HPM effect experiment, which indicates that the analysis in this paper is correct.

Multi-objective evolutionary algorithm based on preference for constrained optimization problems

DONG Ning;WANG Yuping

J4. 2014, 41(1):  98-104+188.  doi:10.3969/j.issn.1001-2400.2014.01.018

Abstract ( 1121 )   PDF (528KB) ( 813 )   Save

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Constrained optimization problems (COPs) are converted into the bi-objective optimization problem and solved with a new preference based multi-objective evolutionary algorithm. A new hybrid crossover operator is proposed to improve the search ability in the evolutionary process, and also a novel fitness function with preference based on the achievement scalarizing function (ASF) which is used in the method of weighted metrics in multi-objective optimization is presented. The new fitness measures the merits of individuals by the weighting distance from individuals to the reference point, where the reference point and the weighting vector afford the preference for selection. In different evolutionary stages, the reference point and weighting vector are chosen adaptively according to the individuals in population to make a tradeoff between the preferences to the two objectives. Numerical experiments for several standard test functions with different characteristics illustrate that the new proposed algorithm is effective and efficient.

New image enhancement algorithm based on the SLIP model

ZHANG Guangyan;WANG Junping;WANG Song;CAO Honghua;XU Dan;LI Jin;LI Changjiang

J4. 2014, 41(1):  105-109+169.  doi:10.3969/j.issn.1001-2400.2014.01.019

Abstract ( 1698 )   PDF (1958KB) ( 768 )   Save

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Image enhancement technology plays an important role in human life, social production, etc. This paper presents a new algorithm for image enhancement based on the SLIP (Symmetric Logarithmic Image Processing) model. Firstly, we get the SLIP image enhancement algorithm about image gray values based on the analysis of the existing logarithmic image enhancement algorithm. Then the SLIP image enhancement algorithm is simplified to the simple mathematical operation using the vector operation of the SLIP model. The proposed algorithm can enhance the image not only with the mode of the transmitted light image but also with the mode of the reflected light image. By means of subjective evaluation and EMEE objective evaluation, experimental results show that the proposed algorithm can enhance the image detail and improve the overall image contrast. Meanwhile, the algorithm overcomes the disadvantage that LIP image enhancement algorithm cannot enhance the images with the mode of the reflected light image.

Sensing insider threat based on access vectors

ZHANG Hongbin;PEI Qingqi;WANG Chao;WANG Meihua

J4. 2014, 41(1):  110-115.  doi:10.3969/j.issn.1001-2400.2014.01.020

Abstract ( 940 )   PDF (580KB) ( 634 )   Save

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The hierarchy-based access control model and access vectors are defined by using the access control relationship. A method is developed for quantizing the insider threat on resources and actions in the information system. Then a full real time assessment is obtained by using access vectors. Compared with other models, this model improves the precision and objectivity of the quantization without a prior knowledge of the system. Experimental results show that the access vector based on the hand hierarchy-based access control model can effectively assess the insider threat in real-time and can be used to build the insider threat sense system.

Cross layer reputation mechanism based secure routing protocol for WMNs

LIN Hui;MA Jianfeng

J4. 2014, 41(1):  116-123.  doi:10.3969/j.issn.1001-2400.2014.01.021

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Wireless mesh networks are faced with various security threats due to their special infrastructure and communication mode, where the internal attacks aiming at routing security and user privacy security are one of the most challenging issues. In this paper a novel cross layer reputation mechanism is first proposed to identify and isolate the internal malicious nodes. Then, a privacy-aware secure routing protocol CR-HWMP based on the proposed reputation mechanism is proposed. Performance analysis and simulation results show that CR-HWMP can effectively implement the privacy preserving and defend against the internal attacks such as black hole and gray hole, and improve the reliability, robustness and security of the wireless mesh networks efficiently.

Histogram shifting based adaptive reversible watermarking algorithm with a high capacity

WANG Xiang;LI Ke;FU Kaiyuan;LUO Fan

J4. 2014, 41(1):  124-129.  doi:10.3969/j.issn.1001-2400.2014.01.022

Abstract ( 905 )   PDF (553KB) ( 689 )   Save

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The traditional histogram shifting based reversible watermarking algorithm can only embed at most 1.0 bit watermark information into one pixel in single-pass embedding. Therefore, we have to use multi-pass embedding to achieve a higher embedding capacity. However, in the second-pass and the subsequent embedding process, the prediction error will be affected by the embedding distortion, which reduces the embedding efficiency. To this end, this paper proposes an improved reversible watermarking algorithm by employing histogram shifting. The algorithm embeds 1.0 bit or more bit watermark in one pixel in terms of the context of image. Experimental results show that the algorithm can effectively improve the embedding capacity while maintaining a high image quality.

Generation and analysis of the excellent 2ⁿ-periodic binary sequences

NIU Zhihua;LI Zheng;LI Zhe;XIN Mingjun

J4. 2014, 41(1):  130-134.  doi:10.3969/j.issn.1001-2400.2014.01.023

Abstract ( 829 )   PDF (435KB) ( 630 )   Save

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The 2ⁿ-periodic binary sequence with high linear complexity and high k-error linear complexity is defined as an excellent sequence. We design a genetic algorithm for generating excellent sequences and studying their features. Choosing the N-periodic binary sequences, where N=8, 16, 32, k=N/4, we search the resulted sequences by the genetic algorithm with various parameters, and compute the linear complexity profiles of results sequences by using the Lauder-Paterson algorithm, to confirm that the obtained sequences are the real excellent sequences. By numerous experiments, we speculate that the k-error linear complexity of the N-periodic binary excellent sequence meets the formula LC_k(S)≤N-2k+1, when k=N/4、N/8 (we also do experiments on sequences with periods 64, 128 and 256). By the brute-force method we obtain that the proportion of the excellent sequence in all binary sequences of the same period is 1/4.

α-generalized resolution principle based on the lattice-valued first-order logic system

XU Weitao;ZHANG Wenqiang;XU Yang;ZHANG Dexian

J4. 2014, 41(1):  135-139.  doi:10.3969/j.issn.1001-2400.2014.01.024

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In the framework of the lattice-valued logic system based on the lattice implication algebra, the α-resolution principle based on the lattice-valued logic system is extended from generalized clauses set to general generalized clauses set. In this paper, the α-generalized resolution principle is presented in the lattice-valued first-order logic system LF(X). At the same time, the soundness theorem is established in LF(X). By using the lift lemma, the weak completeness theorem is also proved. This work can provide a new automated reasoning technology in order to establish novel generalized resolution methods for lattice-valued logic systems.

Novel method for analyzing the performance of the 1bit IR-UWB receiver in the presence of timing jitter

ZHANG Chao;YUE Guangrong;YIN Huarui

J4. 2014, 41(1):  140-146.  doi:10.3969/j.issn.1001-2400.2014.01.025

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A novel method based on the Central Limit Theorem (CLT) is proposed to analyze the performance of the 1bit Impulse-Radio Ultra-WideBand(IR-UWB) receiver in the presence of a timing jitter. First, the sampled signal with timing jitter is expressed as a linear function of the sampled signal without jitter and timing jitter through first-order Taylor series expansion. Then by the CLT, the decision variable of the 1bit receiver is considered as Gaussian distributed and the bit error rate (BER) is derived. After that, an upper bound of the averaged BER is also provided based on the distribution of random timing jitter. The given analytical result is the first analytic expression of the BER performance of the 1bit receiver with timing jitter and can be used for the case where the 1bit receiver has a linear interference. Experimental results show that the proposed upper bound agrees with the actual performance of the 1bit receiver very well and can be used for both Gaussian distributed and uniform distributed timing jitter.

The 3D transmission scheme in DVB-S2

SHAO Yongqing;ZHANG Baiyu;HUANG Yan

J4. 2014, 41(1):  147-152.  doi:10.3969/j.issn.1001-2400.2014.01.026

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According to the characteristics of DVB-S2 streams and 2D data transmission, three kinds of transmission modes based on the data link layer are provided in the DVB-S2 channel, and the corresponding transmission protocol stacks are also given. According to the regulation of transmission modes, the transmission efficiency is calculated in each case and then a comparison is made. Synthesizing various factors, we conclude that each transmission mode has its own advantages and disadvantages in different applications, and that none of them cannot be completely replaced by others.

Polarization-dependent mutiband low RCS reflection screen

YAO Xu;CAO Xiangyu;GAO Jun;ZHAO Yi;YANG Huanhuan

J4. 2014, 41(1):  153-157.  doi:10.3969/j.issn.1001-2400.2014.01.027

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A novel radar reflection screen composed of the polarization-dependent mutiband artificial magnetic conductor (PDMAMC) and perfect electric conductor cells is proposed. The PDMAMC is realized by etching a complementary split ring resonator (CSRR) on the patch of a conventional artificial magnetic conductor. Around the two/three operational frequencies of the PDMAMC-elements for different electric field polarizations, the reflection of the PDMAMC and perfect electric conductor have opposite phases, so for any normal incident plane wave the reflections cancel out. The basic principle is discussed and a sample is measured. The results show that the proposed method is feasible and effective for polarization-dependent mutiband RCS reduction.

Improved sparse multipath channel equation method

YANG Yuan;LI Mingyang;WANG Xuhua

J4. 2014, 41(1):  158-163.  doi:10.3969/j.issn.1001-2400.2014.01.028

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Traditional channel equation methods are based on the multi-path richness hypothesis, which is complicated and inefficient in sparse channels. In this paper, a sparse multi-path channel equation method is proposed. The sparse channel estimation is carried out using a small number of pilot tones based on Compressed Sensing (CS). The equation inverse filter is derived from the channel estimation. The procession of inverse filter solution is modeled as an optimization problem and a greedy algorithm is proposed which can bring about a near optimal solution. The new algorithm requires fewer iterations than linear prediction and gets almost optimal filter parameters when the rank is high enough. The modularized structure of the greedy algorithm is designed which is less complicated and can be easily realized. Simulation shows that the BER performance of the proposed equation method is improved significantly with the increase of SNRs. At 15dB of the SNR it gains 10dB in power efficiency relative to LMS.

SAARS microstrip antenna design with an asymmetrical structure and a tilted beam

LI Sijia;CAO Xiangyu;GAO Jun;ZHENG Qiurong;YANG Huanhuan

J4. 2014, 41(1):  164-169.  doi:10.3969/j.issn.1001-2400.2014.01.029

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A circularly polarized microstrip antenna with the tilted beam of 30° through the asymmetrical structure combing the single-arm archimedean spiral antenna with the helix antenna is constructed in order to make the beam tilted. The bandwidth, tilted beam, and radiation characteristics have been improved through the width optimization and coaxial feed line selection. This antenna can realize the directional radiation of circularly polarized microwaves in a definite frequency band and has a bandwidth of 16.7％ (for Voltage Standing Wave Ratio(VSWR)<2, Axis Ratio(AR)<3dB and the tilted beam of 30°) in the condition of the vertical aperture external excitation with a coaxial feed line. Simulated and measured results show that this antenna has a wideband, high gain, and tilted beam with circularly polarized microwaves.

Actuator placement optimization of optimum vibration control for tensegrity structures

JIANG Jie;LI Tuanjie

J4. 2014, 41(1):  170-175.  doi:10.3969/j.issn.1001-2400.2014.01.030

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The simulated annealing algorithm is employed to implement the actuators placement optimization for a tensegrity structure, and the effect of actuator positioning on the vibration control of the structure is analyzed. To this end, the ANSYS model of a 4-floor tensegrity structure is built, and the state space control equation of the structure through mode transform and mode truncation is deduced. Based on optimal vibration control for the tensegrity structure, the energy of the system with respect to actuator locations is chosen as the optimal criterion. Simulation results indicate that the optimization method is effective, and that the performance of vibration control of the tensegrity structure is improved dramatically when actuators are placed in the optimal position.

Approximated expression for the achievable residual intersymbol interference obtained by multimodulus blind equalizers

WANG Cheng;YANG Bin

J4. 2014, 41(1):  176-181.  doi:10.3969/j.issn.1001-2400.2014.01.031

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A closed approximated formed expression for the achievable residual inter-symbol interference(ISI) is proposed for the adaptive equalizers that adopt the multimodulus algorithm. The expression depends on the step-size parameter, equalizer's tap length, input signal statistics, signal noise ratio and channel power. Simulation proves that the expression shows the exact relationship between residual inter-symbol interference and involved parameters. Since the channel power and signal noise ratio of the expression are measurable or can be calculated, this new approximated expression can be a useful tool for choosing the step-size and tap length for designing an equalizer, and for making direct performance comparison between blind equalizers based on distinct algorithms.

Joint calibration algorithm in the presence of mutual coupling and channel discord via rotational invariance techniques

WANG Ling;LIU Jianqiang;LI Guolin;ZHANG Zhen;YANG Jikun

J4. 2014, 41(1):  182-188.  doi:10.3969/j.issn.1001-2400.2014.01.032

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The performance of subspace estimation algorithms degrades substantially in the presence of mutual coupling and channel discord by the perturbance of the steering matrix. Classical self-calibration algorithms need multidimensional search, optimization and iteration, and large calculation quantity. In order to avoid these shortcomings, a novel joint calibration algorithm using rotational invariance techniques is proposed in this paper. Two sub-arrays' steering matrix can maintain the rotational invariance property in the presence of array errors by switching channels and selecting sub-arrays according to the characteristic of the mutual coupling matrix. So, the estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm is applicable to mutual coupling and channel discord scenarios. The algorithm requires neither searching the spectrum peak nor estimating error parameters, and the calibration of array errors does not need an additional calculation quantity. Simulation results show that the proposed algorithm can restrain mutual coupling and channel discord. The performance of the algorithm is equivalent to the performance of the standard ESPRIT algorithm without errors.