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A new family of windows——convolution windows and their applications

Science china(Technological Sciences) 2005年第4期48卷 468-480页

作者： ZHANG Jieqiu1,2. LIANG Changhong1 & CHEN Yanpu3 1. Department of Applied Math. & Phys., College of Science, Airforce Engineering university, xi’an 710051, china {2., xidian university, xi’an 710071, china 3. Computer Center, xi’an Communication College, xi’an 710106, china Department of Applied Math. & Phys. College of Science Airforce Engineering University national key {2. of antennas and microwave technology Xidian University Computer Center Xi"an Communication College

A new family of windows is constructed by convolutions via a few rectangular windows with same time width and is thus referred to as convolution windows. The expressions of the second-order up to the eighth-order convolution windows in both the time and frequency domains are derived. Their applications in high accuracy harmonic analysis of periodic signals are investigated. Comparisons between the proposed windows and some known windows with the same width shows that, when the synchronous deviation of data sampling is slight, the proposed ones have the least effect of spectral leakage. Therefore, the new windows are well suited for high accuracy harmonic analysis and parameter estimation for periodic signals. The error analysis and computer simulations show that the estimation errors, corresponding to frequency, amplitude and phase of every harmonic component of a signal, are proportional to the pth power of the relative frequency deviation in case of the pth-order convolution window is applied to windowing signal of approximately p cycles. By introducing real time adjustment in sampling interval, the proposed algorithm can adaptively trace signal frequency and lead to less sampling synchronous deviation. The proposed approach has the advantages of easy implementation and high measure precision and can be used in harmonic analysis of quasi-periodic signals whose fundamental frequency drifts slowly with time.

关键词： signal processing harmonic analysis window function convolution window synchronous error spoctral leakage

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Fast algorithm based on triplet Markov fields for unsupervised multi-class segmentation of SAR images

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Science china(Information Sciences) 2011年第7期54卷 1524-1533页

作者： WU Yan 1,WANG xin 1,xiAO Ping 2.GAN Lu 1,LIU ChunYan 1 & LI Ming 3 1 School of Electronics Engineering,xidian university,xi’an {2.,china 2.Shaanxi Bureau of Surveying & Mapping,xi’an 710054,china 3 national key laboratory of Radar Signal Processing,xidian university,xi’an {2.,china School of Electronics Engineering Xidian University Shaanxi Bureau of Surveying & Mapping

Non-Gaussian triplet Markov fields (TMF) model is suitable for dealing with multi-class segmentation of non-stationary and non-Gaussian synthetic aperture radar (SAR) *** the complexity of the model and algorithm,as well as the requirement of real-time,and robust and efficient processing of SAR images,a fast algorithm based on TMF for unsupervised multi-class segmentation of SAR images is proposed in this *** the speckle noise in SAR images,numerical characteristic,threshold selection and QuadTree decomposition criterion are researched *** the new method,a SAR image can quickly be mapped into an edge-based pixon-representation,which results in a coarse decomposition in smooth regions,and a fine decomposition in *** by combining TMF model with the pixon-representation of SAR image,a new potential energy function of TMF based on pixon-representation is ***,the segmentation is finished by Bayesian maximum posterior mode (MPM).The effectiveness of the fast TMF algorithm is demonstrated by applying it to simulated data and real SAR images.

关键词： pixon-representation of SAR image QuadTree decomposition new potential energy function triplet Markov fields multi-class segmentation

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Exact thresholds for low-density parity-check codes over the binary erasure channel

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Progress in Natural Science:Materials International 2009年第7期19卷 897-900页

作者： Jianjun Mu a, xiaopeng Jiao a, xinmei Wangb a School of Computer Science and technology, xidian university,{2., china b State key laboratory of Integrated Service Networks, xidian university,{2., china School of Computer Science and technology Xidian University Xi’an 710071 China State key laboratory of Integrated Service Networks Xidian University Xi’an 710071 China

A simple method for determining the threshold of irregular LDPC codes over the binary erasure channel (BEC) under message-passing decoding is proposed. An exact formula for calculating the threshold of irregular LDPC codes over the BEC is proved. This generalizes the known result on the threshold of regular LDPC codes to irregular LDPC codes. Moreover, our new method can avoid the computation of the inverse of the degree distribution function for irregular LDPC codes. Numerical results demonstrate the correctness of our proposed method.

关键词： Binary erasure channel (BEC) LDPC codes Threshold

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An eigenstructure-based 2. DOA estimation method using dual-size spatial invariance array

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Science china(Information Sciences) 2011年第1期54卷 163-171页

作者： YANG XueYa,CHEN Baixiao & CHEN YunHai national key Lab of Radar Signal Processing,{2. university,xi’an 710071,china national key Lab of Radar Signal Processing Xidian University

A sparse planar array vertically placed in y-z plane is proposed to improve the angle estimation accuracy of sources in low angle region with reflection *** two sizes of spatial invariances along both dimensions,the array estimates the azimuth and elevation angles using unitary ESPRIT(estimation of signal parameters via rotational invariance techniques).The first spatial invariance with a displacement of half-wavelength yields unambiguous coarse estimates of high-variance,while the second spatial invariance with much larger a displacement of subarrays obtains cyclically ambiguous fine estimates of *** final estimates are obtained by disambiguating fine estimates with coarse estimates.A novel pairing scheme is proposed to pair both the azimuth and elevation,coarse and fine angle estimates of the same *** addition, a new method is presented to calculate 2. angles,which substitutes the estimated elevation angle into the sin relative to the y-axis to get the azimuth *** real-valued processing and array aperture extension, the new DOA measuring method de-correlates the multipath signals and enhances angle resolution with no extra antennas and computational *** results show the effectiveness of the proposed technique and its advantages over the conventional methods.

关键词： DOA estimation sparse array correlated signals unitary ESPRIT dual-size spatial invariances

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ISAR imaging via sparse frequency-stepped chirp signal

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Science china(Information Sciences) 2012年第4期55卷 877-888页

作者： WANG Hongxian,LIANG Yi,xiNG MengDao & ZHANG ShouHong national key {2. of Radar Signal Processing,xidian university,xi’an 710071,china national key {2. of Radar Signal Processing Xidian University

Frequency-stepped chirp signal can simplify the designation of radar ***,it has a shortcoming of Doppler ambiguity for high-speed moving ***,it is of great significance to study how to increase its equivalent pulse repeat *** back scattering field of the ISAR target has strong sparsity;that is to say,most energy is contributed merely by a few scattering ***,based on the theory of the sparse signal representation,a novel method for ISAR imaging via sparse frequency-stepped chirp signals is proposed by analyzing the signal model of the *** the proposed method,part of sub-pulses of the frequency-stepped chirp signal is randomly selected to transmit,and then the 2. high-resolution image of the target can be constructed by sparse signal *** the cost of computational resources,the method can effectively resolve the problem of Doppler ambiguity,decrease the sidelobes and obtain a super-resolution ***,the validity of the proposed approach is confirmed by the results of numerical simulations and real data.

关键词： inverse synthetic aperture radar (ISAR) radar imaging sparse signal representation frequency-stepped (FS)

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A class of quasi-cyclic LDPC codes from B2.（mod m） sequences

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Science china(Information Sciences) 2011年第8期54卷 1645-1653页

作者： ZHANG GuoHua & WANG xinMei State key laboratory of Integrated Service Network,{2. university,xi’an 710071,china State key laboratory of Integrated Service Network Xidian University

A new class of binary low-density parity-check (LDPC) codes is proposed based on B 2.(mod m) sequences. The parity-check matrix of such a code has a column weight of three and a row weight of an arbitrary integer,and a quasi-cyclic *** parity-check matrix also has a girth at least 8,and corresponds to a code with minimal distance at least *** m is prime,an 8-cycles reduction method is presented to completely avoid the two types of 8-cycles within the total four types existed in the Tanner *** results show that,for a prime integer m,the new LDPC code outperforms the random (quasi-) regular counterpart generated by the PEG ***,a heuristic algorithm based on a strategy called neighboring extension search is presented to search for the B 2.(mod m) sequences whose lengths approach or meet the upper bound.

关键词： channel coding LDPC code B2.(mod m) sequencegirth

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Threshold proxy quantum signature scheme with threshold shared verification

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Science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 1079-1088页

作者： YANG YuGuang1,3,4 & WEN QiaoYan2.1 College of Computer Science and technology,Beijing university of technology,Beijing 10012.,china 2.State key laboratory of Networking and Switching technology,Beijing university of Posts and Tele-communications,Beijing 100876,china 3 State key laboratory of Integrated Services Network,xidian university,xi’an 710071,china 4 State key laboratory of Information Security(Graduate university of Chinese Academy of Sciences) ,Beijing 100049,china College of Computer Science and technology Beijing University of Technology Beijing China State key laboratory of Integrated Services Network Xidian University Xi’an China State key laboratory of Information Security (Graduate {2. of Chinese Academy of Sciences) Beijing China State key laboratory of Networking and Switching {2. Beijing University of Posts and Telecommunications Beijing China

A threshold proxy quantum signature scheme with threshold shared verification is proposed. An original signer could authorize a group as its proxy signers. Then only t or more of n persons in the proxy group can generate the proxy signature on behalf of the original signer and any t-1 or fewer ones cannot do that. When the proxy signature needs to be verified,any t or more of n persons belonging to the verification group can verify the message and any t-1 or fewer ones cannot verify the validity of the proxy signature.

关键词： quantum signature threshold proxy quantum group signature threshold shared verification

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Quantum threshold group signature

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Science china(Physics,Mechanics & Astronomy) 2008年第10期51卷 1505-1514页

作者： YANG YuGuang1,2.3 & WEN QiaoYan4 1 College of Computer Science and technology, Beijing university of technology, Beijing 10012., china 2.State key laboratory of Integrated Services Network, xidian university, xi’an 710071, china 3 State key laboratory of Information Security (Graduate university of Chinese Academy of Sciences), Beijing 100049, china 4 State key laboratory of Networking and Switching technology, Beijing university of Posts and Tele-communications, Beijing 100876, china College of Computer Science and technology Beijing University of Technology Beijing China State key laboratory of Integrated Services Network Xidian University Xi’an China State key laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing China State key laboratory of Networking and Switching {2. Beijing University of Posts and Telecommunications Beijing China

In most situations, the signer is generally a single person. However, when the message is written on behalf of an organization, a valid message may require the approval or consent of several persons. Threshold signature is a solution to this problem. Generally speaking, as an authority which can be trusted by all members does not exist, a threshold signature scheme without a trusted party appears more attractive. Following some ideas of the classical Shamir’s threshold signature scheme, a quantum threshold group signature one is proposed. In the proposed scheme, only t or more of n persons in the group can generate the group signature and any t-1 or fewer ones cannot do that. In the verification phase, any t or more of n signature receivers can verify the message and any t-1 or fewer receivers cannot verify the validity of the signature.

关键词： threshold quantum signature trusted party quantum cryptography

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Threshold quantum secret sharing between multi-party and multi-party

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Science china(Physics,Mechanics & Astronomy) 2008年第9期51卷 1308-1315页

作者： YANG YuGuang1,2.3 & WEN QiaoYan4 1 College of Computer Science and technology,Beijing university of technology,Beijing 10012.,china 2.State key laboratory of Integrated Services Network,xidian university,xi’an 710071,china 3 State key laboratory of Information Security (Graduate university of Chinese Academy of Sciences),Beijing 100049,china 4 State key laboratory of Networking and Switching technology,Beijing university of Posts and Tele-communications,Beijing 100876,china College of Computer Science and technology Beijing University of Technology Beijing China State key laboratory of Integrated Services Network Xidian University Xi’an China State key laboratory of Information Security (Graduate {2. of Chinese Academy of Sciences) Beijing China State key laboratory of Networking and Switching {2. Beijing University of Posts and Telecommunications Beijing China

A threshold quantum secret sharing (TQSS) scheme between multi-party and multi-party was proposed using a sequence of single photons,which is useful and efficient when the parties of communication are not all present. We described the process of this TQSS scheme and discussed its security. It was shown that entan-glement is not necessary for quantum secret sharing. Moreover,the theoretic effi-ciency was improved to approach 100% as almost all the instances can be used for generating the private key,and each photon can carry one bit of information. This protocol is feasible with the present-day technique.

关键词： threshold quantum secret sharing quantum cryptography single photon multi-party and multi-party

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A novel distortion elimination method of power amplifier in wideband OFDM system

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Science china(Information Sciences) 2012年第2期55卷 396-406页

作者： REN ZhiYuan & ZHANG HaiLin State key laboratory of integrated services network,{2. university,xi’an 710071,china State key laboratory of integrated services network Xidian University

The nonlinear,memory and saturate distortion caused by power amplifier lead to low BER per-formance and low power efficiency in wideband OFDM *** solve the related problems,a novel power amplifier based on combined amplification with multi power amplifiers is proposed in this *** addition,a novel simplified filter look-up table predistorter is *** novel predistorter connects to a memoryless predistorter subsystem with an adaptive filter subsystem in cascade,and can eliminate the nonlinear memory distortion *** simulation results indicate that the power efficiency and BER performance will be improved by using the novel amplifier structure together with the novel predistorter.

关键词： wideband OFDM dynamic range extended memory predistorter

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