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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. {3. {2. {2. of antennas and microwave Technology, xidian university, xi’an 710071, China 3. Computer Center, xi’an Communication College, xi’an 710106, China 1. Department of Applied Math. & Phys. College of Science Airforce Engineering University 710051 Xi’an China 2. national key {2. of {2. and microwave Technology Xidian University 710071 Xi’an China 3. Computer Center Xi’an Communication College 710106 Xi’an China

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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Performance improvement in multi-ship imaging for ScanSAR based on sparse representation

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Science China(Information Sciences) 2012年第8期55卷 1860-1875页

作者： XU Gang1,SHENG JiaLian1,ZHANG Lei1&xiNG MengDao1,2.1N ational key laboratory of Radar Signal Processing,{2. {2.,xi'an 710071,China 2.5} key laboratory of microwave Imaging,Institute of Electronics,Chinese Academy of Sciences,Beijing 100080,China 1. national key {2. of Radar Signal Processing Xidian University Xi’an 710071 China2. National Key Laboratory of Microwave Imaging Institute of Electronics Chinese Academy of Sciences Beijing 100080 China

There is always a compromise between unambiguous wide-swath imaging and high cross-range resolution owing to the constraint of minimum antenna area for conventional single-channel spaceborne synthetic aperture radar(SAR)*** overcome the inherent systemic limitation,multi-channel SAR imaging has been ***,this still suffers from various problems such as high system *** simplify the system structure,a novel algorithm for high resolution multi-ship ScanSAR imaging based on sparse representation is proposed in this paper,where the SAR imaging model is established via maximum a posterior estimation by utilizing the sparsity prior of multi-ship *** the scheme,a wide swath is generated in the ScanSAR mode by continuously switching the radar footprint between ***,high crossrange resolution is realized from sparse subapertures by exploiting the sparsity feature of multi-ship *** particular,the SAR observation operator is constructed approximately as the inverse of conventional SAR imaging and then high resolution SAR imaging including range cell migration compensation is achieved by solving the *** with multi-channel SAR imaging,the system complexity is effectively reduced in the ScanSAR *** addition,enhancement of the cross-range resolution is realized by incorporating the sparsity prior with sparse *** a result,the amount of data is effectively *** based on measured data have been carried out to confirm the effectiveness and validity of the proposed algorithm.

关键词： synthetic aperture radar(SAR) ScanSAR wide-swath sparse representation high resolution

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Super-orthogonal space-time code design based on the trellis diagram integrated operation

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Science China(Information Sciences) 2011年第7期54卷 1481-1490页

作者： AO Jun 1,2.MA ChunBo 1,AO FaLiang 1 & LIAO GuiSheng 3.1 College of Information and Communication,Guilin university of Electronic and Technology,Guilin 541004,China 2.{3. {2. {2. of Electromagnetic Environment,QingDao,2.6107,China 3.{3. Lab of Radar Signal Processing,xidian university,xi’an 710071,China 1. College of Information and Communication Guilin University of Electronic and Technology Guilin 541004 China2. National Key Laboratory of Electromagnetic Environment QingDao 266107 China3. National Lab of Radar Signal Processing Xidian University Xi’an 710071 China

By studying the super-orthogonal space-time coding designs for 2.transmit antennas and superquasi orthogonal space-time coding designs for 4 transmit antennas,a novel super-orthogonal space-time coding design for 4 transmit antennas is *** exploiting the inherent structure association between OSTBC and QOSTBC,the proposed schemes can obtain the full-rate and good performance while keeping the coding complexity as super-orthogonal space-time coding schemes for 2.transmit *** results demonstrate that the proposed schemes outperforms the existing super-quasi orthogonal space-time coding schemes by almost 2.dB.

关键词： STBC TCM SOSTTC SQOSTTC

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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. {3.,xi’an 710071,China 1. national key Lab of Radar Signal Processing Xidian University Xi’an 710071 China

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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COMPENSATION FOR THE EFFECTS OF MUTUAL COUPLING ON THE PERFORMANCE OF ADAPTIVE ARRAYS

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Journal of Electronics(China) 2002年第1期19卷 76-80页

作者： Gao Xue Hu Hongfei Fu Demin (national key Lab. of {2. and {3. Technology, xidian university, xi’an 710071) national key Lab. of {2. and {3. Technology Xidian University Xi'an 710071

Using the Method of Moments(MoM) and the spectral method, the effect of mutual coupling on the performance of adaptive arrays is compensated. First, the MoM is used to compute the behavior of the array, where the accurate analytical model and odd numbers of piecewise sinusoids are applied. Then the covariance matrix with mutual coupling being taken into account is analyzed, and the expression for the weight of the Least Mean Square(LMS) algorithm with mutual coupling being compensated is given. Finally, the method given in this letter is tested on an example.

关键词： Method of moment Spectral method Equivalent model Mutual coupling Com-pensation

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ANALYSIS OF THE EFFECT OF THE TRUNCATED SCAN PLANE IN TIME-DOMAIN NEAR-FIELD MEASUREMENTS

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Journal of Electronics(China) 2002年第1期19卷 89-93页

作者： Hu Hongfei Gao Xue Fu Demin(national key Lab. of {2. and {3. Technology, xidian university, xi’an 710071) national key Lab. of {2. and {3. Technology Xidian University Xi'an 710071

The thought and formulation for near-field far-field transformation based on the direct time-domain computation scheme are given. The effect of the truncated scan plane is investigated by simulating time-domain measurement of an open-ended waveguide antenna, and a simple and effective criterion is derived for removing the truncation errors in the practical time-domain near-field measurements.

关键词： Near-field measurement Time-domain Truncation effect

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MODE THEORY OF MULTILAYER WAVEGUIDE STRUCTURE WITH DISCONTINUITIES

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Journal of Electronics(China) 2003年第3期20卷 237-240页

作者： Zong Weihua Liang Changhong (national key Lab of Antenna and {2. Technology,{3., xi’an 710071) national key Lab of Antenna and {2. Technology Xidian University Xi'an 710071

TEn mode (whose electric field is zero in the normal direction of the boundaries between layers) and TMn mode (whose magnetic field is zero in the normal direction of the boundaries between layers) are defined. Then conditions under which pure TEn (TMn) modes may exist in multilayer waveguide structure with discontinuities are presented. E (H) step wavguides, ridged wavguides, microstrip lines and fin lines all satisfy the conditions, and hold for TEn (TMn) mode. The conventional conclusion that ridged waveguides with inhomogeneous dielectric-slab loading, microstrip lines and fin lines only hold for hybrid modes is revised. Compared with hybrid modes, the number of unknown variations and matching equations is reduced by half for pure TEn (TMn) modes, and the computation cost is decreased dramatically.

关键词： Multilayer waveguide structure Discontinuity Higher order mode TEn mode TMn mode

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CPW-Fed Ultrawideband Antenna With 3.5/5.5 GHz Dual BandNotched Characteristics

CPW-Fed Ultrawideband Antenna With 3.5/5.5 GHz Dual BandNotc...

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2.11 IEEE International Conference on microwave Technology & Computational Electromagnetics(ICMTCE 2.11)

作者： Wei Zhang Yong-Chang Jiao Bin Yang Zhen Hong national key {2. of {3. and microwave Technology xidian university xi’an Shaanxi 710071 China

A compact coplanar waveguide （CPW） fed ultra wideband （UWB） printed monopole slot antenna with 3.4/5.5 GHz dual band-notched characteristics is proposed in this *** antenna consists of a semi-circular and rectangular combined metal patch and 50 coplanar waveguide （CPW） transmission line on the front side of the substrate.A C-shaped and a modified-shaped slot etched in the patch to produce two notched bands at the center frequencies of 3.5 and 5.5 GHz in the UWB *** computer simulation results of the Voltage-Standing-Wave Ratio （VSWR）,radiation pattern and peak gain of the antenna agree well with the measurements.

关键词： Dual band-notched -shaped and C-shaped slot coplanar waveguide (CPW) fed ultra wideband (UWB) antenna

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Application of the Window Function in the Plane Wave Synthesis Technique

Application of the Window Function in the Plane Wave Synthes...

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2.06 7th International Symposium on antennas, Propagation and EM Theory

作者： Yu Ding, Fu Demin, Liu Qizhong, Mao Naihong national laboratory of {2. and {3. Technology, xidian university, xi'an 710071, China

The cosine window function is introduced and applied in the plane wave synthesis technique. With the infinite long current filament as the scanning probe, the plane wave synthesis technique is computer simulated The calculation results show that in the plane wave synthesis technique, the uniform degree of the amplitude and phase of the quasi-plane wave synthesized in the body under test zone can be improved greatly by weighting process of the current distribution of the array elements with the cosine window function, which proves the validity and applicability of the weighting method by means of the cosine window function in the plane wave synthesis technique.

关键词： Application of the Window Function in the Plane Wave Synthesis Technique

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A Ka Dual-Band Circular Waveguide Polarizer

A Ka Dual-Band Circular Waveguide Polarizer

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2.06 7th International Symposium on antennas, Propagation and EM Theory

作者： Tian-ling Zhang Ze-hong Yan national laboratory of {2. and {3. Technology, xidian university, xi'an, 710071, PR. China

The design of a Ka dual-band circular polarizer by inserting a dielectric septum in the middle of the circular waveguide is discussed here. The dielectric septum is located in fixing slots, and by adjusting the dimension of the dual-compensation slots which are built in the orthogonal plane, the phase difference of 90° at the center frequency for the dual-band can be achieved. Furthermore, the gradual changing structures at both ends of the dielectric septum are built for impedance matching for both Ex and Ey polarizations. The simple structure of this kind of polarizer can reduce the influence of manufacturing inaccuracy in the Ka-band. The measured phase difference is within 90°± 4.5° for both bands. In addition, the return losses for both Ex and Ey polarizations are better than -15dB

关键词： Circular polarizer, dielectric septum, dual-compensation slots.

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