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| 1 | Array-error estimation method for multi-channel SAR systems in azimuth显示文摘For multi-channel synthetic aperture radar(SAR) systems, since the minimum antenna area constraint is eliminated,wide swath and high resolution SAR image can be achieved.However, the unavoidable array errors, consisting of channel gainphase mismatch and position uncertainty, significantly degrade the performance of such systems. An iteration-free method is proposed to simultaneously estimate position and gain-phase errors.In our research, the steering vectors corresponding to a pair of Doppler bins within the same range bin are studied in terms of their rotational relationships. The method is based on the fact that the rotational matrix only depends on the position errors and the frequency spacing between the paired Doppler bins but is independent of gain-phase error. Upon combining the projection matrices corresponding to the paired Doppler bins, the position errors are directly obtained in terms of extracting the rotational matrix in a least squares framework. The proposed method, when used in conjunction with the self-calibration algorithm, performs stably as well as has less computational load, compared with the conventional methods. Simulations reveal that the proposed method behaves better than the conventional methods even when the signal-to-noise ratio(SNR) is low. | Lun Ma Guisheng Liao Aifei Liu Yanling Jiang Ling Chen | 2016 | Journal of Systems Engineering and Electronics2016，27，4： | 1 |
| 2 | An eigenstructure method for estimating DOA and sensor gain-phase errors显示文摘 | Aifei Liu Guisheng Liao | 2011 | IEEE Tram on Signal Processing2011，59，12： | 1 |
| 3 | Robust direction-of-arrival estimation method with high accuracy for single vector sensor显示文摘The phase errors among the components of a single acoustic vector sensor cause the direction-of-arrival(DOA) estimation error of the existing methods.In order to address this issue,a DOA estimation method is proposed,which is robust to the phase errors.The proposed method first utilizes the Hadamard product of the principal eigenvector of the covariance matrix of the received signal by the single vector sensor and its conjugate vector to construct the spatial spectrum in order to estimate the DOA of the underwater target.Since the Hadamard product eliminates the phase errors,this estimation is independent of the phase errors.However,it is ambiguous.Afterwards,the phase-error estimate is explored to eliminate the ambiguity and get the correct DOA estimate.The proposed method performs independently of the phase errors and obtains high accuracy.The simulation results and the experimental result demonstrate the proposed method is robust to the phase errors.Furthermore,in the presence of the phase errors,it performs better than the average acoustic intensity method,the CAPON method,and the MUSIC method,in terms of estimation accuracy.In addition,the simulation results indicate that the estimation accuracy of the proposed method approaches to the Cramer-Rao bound(CRB). | LIU Aifei YANG Desen SHI Shengguo LI Sichun LI Ying | 2021 | Chinese Journal of Acoustics2021，40，1： | 0 |
| 4 | DOA Estimation Method Using Sparse Representation with Orthogonal Projection显示文摘In order to reduce the effect of noises on DOA estimation,this paper proposes a direc-tion-of-arrival(DOA)estimation method using sparse representation with orthogonal projection(OPSR).The OPSR method obtains a new covariance matrix by projecting the covariance matrix of the array data to the signal subspace,leading to the elimination of the noise subspace.After-wards,based on the new covariance matrix after the orthogonal projection,a new sparse representa-tion model is established and employed for DOA estimation.Simulation results demonstrate that compared to other methods,the OPSR method has higher angle resolution and better DOA estima-tion performance in the cases of few snapshots and low SNRs. | Fujia Xu Aifei Liu Shiqi Mo Song Li | 2021 | Journal of Beijing Institute of Technology2021，30，4： | 0 |
| 5 | Large-scale synthesis of isolated Mn2O_(3) nanotube/fiber with ferric nitrate as catalyst显示文摘Isolated Mn2O_(3) nanotubes and nanofibers were prepared very easily at a large scale with the liquid-phase catalysis method.The Mn2O_(3) nanotubes had dimensions of 30–50 nm(exterior diameter)and 0.2–1.0 mm(length),approximately.The Mn2O_(3) nanofibers had dimensions of 10–30 nm(diameter)and 0.4–2.0 mm(length),approxim-ately.Nano-Mn2O_(3) with different microstructures including nanotubes,nanofibers and nanoparticles could be selectively synthesized by controlling the contents and proportions of potassium permanganate and ferric nitrate.Ferric nitrate was an ideal catalyst for the preparation of Mn2O_(3) nanotube/fiber.When cobalt nitrate or nickel nitrate was used as catalyst,only amorphous nano-Mn2O_(3) was synthesized.X-ray diffraction(XRD)result shows that the Mn2O_(3) nanotube has a crystalline structure different from o-Mn2O_(3),t-Mn2O_(3),h-Mn2O_(3) and c-Mn2O_(3). | ZHANG Aifei LIU Jiping LÜ Guangshu | 2007 | Frontiers of Chemical Science and Engineering2007，1，1： | 0 |
| 6 | MUSIC-based direction of arrival estimation methods with virtual source elimination for single vector sensor in isotropic ambient noise显示文摘In the scenario of isotropic ambient noise,the inequality between the noise powers of the pressure and velocity channels of a single acoustic vector sensor causes a virtual source for subspace-based methods,which seriously degrades the performance of the conventional multiple signal classification(MUSIC) method.In order to solve this problem,an increased-rank MUSIC method and a weighted-amplitude MUSIC method are presented.The increased-rank MUSIC method augments the dimension of the signal subspace to eliminate the effect of the virtual source.Among the increased-rank,weighted-amplitude,and conventional MUSIC methods,the increased-rank MUSIC method gains the highest estimation accuracy in the cases of one source.Moreover,its performance approaches to the the Cramer-Rao bound(CRB).However,it fails in the case of two sources.The weighted-amplitude MUSIC method weights the amplitude of the received signal to eliminate the virtual source and it can identify two sources. | LIU Aifei YANG Deseng SHI Shengguo ZHU Zhongrui | 2019 | Chinese Journal of Acoustics2019，38，4： | 0 |
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