Time filter

Source Type

Zhang L.,University of Science and Technology Beijing | Zhang F.-C.,University of Science and Technology Beijing | Wang B.,Beijing Institute of Satellite Information Engineering
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

Aiming to improve the performance of transmitted reference(TR) UWB system and mitigate external interference in multipath channel, time reversal(TiR) is employed. The BER performance of TR-UWB systems with and without TiR technology are investigated respectively, and the results imply that the SNR of TR-UWB system is improved about 10dB in multi-path channel with TiR pre-filter than that without TiR pre-filter whilst BER=1E-3. The impacts of the notch filter's parameters on performance of TiR TR-UWB system are investigated. The simulation results show that every increase of 528MHz in the width of notch filter causes 5dB degradation in the performance whilst the depth of notch filter has little influence on it. Finally, BER performance of this system with notch filter is studied in the case of MB-OFDM-UWB interference. Results indicate that with ultra-wideband notch filter technology, strong ultra-wideband interference within a bandwidth of 3×528MHz can be mitigated. For BER=1E-2, the signal-to-interference ratio(SIR) of TR-UWB improves 25dB with a notch filter comparing to that without a notch filter. The present work is expected to be useful for the design of the simple and advanced TR-UWB system. © 2013 Springer-Verlag Berlin Heidelberg. Source

Xu X.,Beijing University of Posts and Telecommunications | Dai J.,Beijing University of Posts and Telecommunications | Dai Y.,Beijing University of Posts and Telecommunications | Yin F.,Beijing University of Posts and Telecommunications | And 5 more authors.
Optics Letters | Year: 2015

In this Letter, we propose and experimentally demonstrate a novel broadband and wide-range feedback tuning scheme for phase-locked loop (PLL) stabilization of tunable optoelectronic oscillators (OEO). The proposed scheme was realized in a simple and feasible way based on a dualparallel Mach-Zehnder modulator (DPMZM) and optical bandpass filter (OBPF). The wide RF phase-shift range and broadband performance of the proposed scheme were demonstrated theoretically and experimentally, which ensured OEO's wide operating temperature range and tunability in PLL stabilization. As a result, PLL stabilization for OEO was achieved at different oscillating frequencies and the long-term stability was greatly improved without any thermal control. The measured overlapping Allan deviation of PLL-locked OEO reached lower than 10-10 after 1000-s averaging time, which was four orders of magnitude better than the free-running OEO. The phase noise performance was also improved at low-offset frequencies and remained the same at high-offset frequencies. © 2015 Optical Society of America. Source

Zheng N.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Zheng N.,Beijing Institute of Satellite Information Engineering | Lu F.,Beijing Institute of Satellite Information Engineering
Lecture Notes in Geoinformation and Cartography | Year: 2012

Traditional solutions to shortest path problems on time-varying transportation networks use traffic information only at precise moments regardless of considering the fact that the travel time through any link is dependent on the time entering that link. In this study, travel speed rather than travel time on each link is used as the time period dependent parameter to model time-dependent transportation networks, and a First-In-First-Out (FIFO) condition satisfied computational function of link travel time is then deduced based on kinematics. Finally, a temporally adaptive A* shortest path algorithm on this FIFO network is presented, where the time factor is introduced into the evaluation function, and the Euclidean distance divided by the maximum possible travel speed is used as a heuristic evaluator. An experiment on a real road network shows that the proposed algorithm is capable of foreseeing and bypassing forthcoming traffic congestion, at a cost only about 10% more in computational time than the traditional algorithm. In addition, frequent path reoptimization required with use of the traditional algorithm is effectively avoided.©Springer-Verlag Berlin Heidelberg 2012. Source

Tian L.,Beijing Institute of Satellite Information Engineering | Fan S.,Beijing Institute of Satellite Information Engineering
Zhongguo Kongjian Kexue Jishu/Chinese Space Science and Technology | Year: 2010

The mixed programming for Nonlinear Chirp Scaling (NCS) algorithm was designed according to the requirements of space borne Synthetic Aperture Radar (SAR) real-time and near-real-time imaging. The two-level pipelined parallel imaging of multi-process and multi-thread with Message Passing Interface (MPI) and Pthread was researched and implemented on SMP cluster. Through the experiments on HP cluster, it is proved that the mixed program imaging algorithm can not only adapt to the instance that the time of one block of original echo data transferred from the front system is more than or equal to eight seconds, but also the instance that a great number of original echo data has been already accumulated. Source

Li H.-C.,Beijing Institute of Satellite Information Engineering | Song H.-F.,Beijing Institute of Satellite Information Engineering
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

The linear array CCD camera is the main sensor on the push-broom satellite. Because of the difference response among the CCD detectors, the striping noise is an obvious phenomenon in the remote sensing image along the scanning direction, which can seriously affect the image quality and quantitative application. The object of relative radiometric calibration is to eliminate them. As the state of satellite electronics varies from orbit to orbit, an automatic de-striping algorithm is needed that depends only on information that can be attained from the image data. There are many published techniques that are used to remove striping from images such as the histogram matching, histogram equalization, and Fourier transform filter methods. In order to decrease the effect we try to remove these stripes in CCD images using a relative radiometric correction algorithm based on the adaptive filtering pattern in this paper. Firstly, aiming at the characteristics of strip noise in push-broom scanner, the cause of strip noise formation is described. The suitable 1-D nonlinear filter is chosen to remove the obvious stripping based on the stripping distribution. Then, 1-D smoothing filtering is used to calculate the gain and offset coefficients. At last, the thin stripping is de-striped with the obtained coefficients. The final results indicate that the proposed method can effectively remove the stripping noise along the scanning direction effectively. Comparison of mean value and standard deviations obtained from the strip noise removed image by the proposed method and histogram equalization method suggested that the proposed method is evidently superior to the traditional histogram equalization method in preserving the image detail very well. The result of this study is applicable in striping removal of push-broom satellite's remote sensing data. © 2011 SPIE. Source

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