Time filter

Source Type

Zhang T.,Tsinghua University | Zhao H.,Beijing Global Information Center | Cui X.,Tsinghua University | Lu M.,Tsinghua University
Lecture Notes in Electrical Engineering

With the application of satellite navigation becoming more and more widely, increasingly complex electromagnetic environment needs to be dealt with. The anti-jamming capabilities of satellite navigation receivers have got more and more attention, whether in the field of military or civilian. The most important and most widely used class of anti-jamming technology is pre-correlation anti-jamming mean. However, the upper bound of overall anti-jamming capability is less studied when the anti-jamming filter inserted into a digital satellite receiver. In this paper the upper bound of anti-jamming capability for pre-correlation anti-jamming receivers is studied. First of all, the quantization loss is theoretically derived, when the input interference is a continuous wave (CWI). A near-optimal quantization interval criterion is proposed through analyzing the minimize quantization loss. Also, according to the calculation of signal-to-noise ratio (SNR) chain in the receiver, the maximum anti-jamming capability is obtained under the constraint of specified quantization bits and quantization interval. The analysis of the upper bound of anti-jamming capability is very important for the design of anti-jamming receivers, and also improves the anti-jamming theory for all spread spectrum signal receivers. © 2012 Springer-Verlag. Source

Yi G.,Beijing Global Information Center | Yi G.,Beihang University | Ming F.,Beihang University
Lecture Notes in Electrical Engineering

Space-time interference suppression technique shows great predominance compared with other anti-jamming techniques. LCMV (Linearly Constrained Minimum Variance) criterion is often used in space-time adaptive processing. Beaming steering and null steering methods were deeply analyzed on LCMV criterion. A new space-time anti-jamming method is proposed combining beam steering and null steering. The method reduces the signal loss of satellite signal DOA estimation error compared with beaming steering and improves the output SINR compared with null steering. Numerical simulation demonstrates that the proposed method is effective and efficient. © 2012 Springer-Verlag. Source

Fan M.,No 2 Institute Of Engineering Corps | Guo Y.,Beijing Global Information Center | Yun C.,Beihang University | Song D.-Z.,Beihang University | Gao Z.-H.,Beihang University
Xitong Fangzhen Xuebao / Journal of System Simulation

Dealing with a dynamic routing planning problem of the intelligent access system used in pharmacy, the mathematical formulations were proposed and an hybrid algorithm for this problem was designed. The designed algorithm incorporated the genetic algorithm and particle swarm algorithm and recommended dynamic adjustment and self-adaptive evolution strategies. The previous of the particle algorithm, with dynamic changing of the inertia weight, other parameters also made adjustments to improve search efficiency and search accuracy. In the latter part of the genetic algorithm, with self-adaptive parameter adjustment strategy, the amount of routing information could be maximized according to each iteration, and the search could be driven towards diverse regions of the solution space. The performance of the proposed algorithm was tested on some intelligent access system instances. It proves to be more effective and efficient than other algorithm. Source

Zhang X.,Tsinghua University | Zhang X.,Beijing Global Information Center | Yao Z.,Tsinghua University | Lu M.,Tsinghua University
Science China: Physics, Mechanics and Astronomy

Satellite navigation is playing an important role in social life. The performances of the services a navigation system provides are the concern of the builders and users. The signal structure determines the inherent ability of a satellite navigation system to provide these services. Therefore, it is necessary and reasonable to optimize the signal in the initial design. The waveforms of signals in satellite navigation chips are an important aspect of the signal's structure, which impact the characteristics of the autocorrelation function and power spectrum in the time domain and frequency domain. The range accuracy of a navigation system is usually described by its Gabor Bandwidth. The Gabor Bandwidth of the Binary Offset Carrier (BOC) modulation in next-generation GNSS signal systems is not optimal. This paper presents a signal expression based on Multilevel Coded Symbol (MCS) signals, which can describe the fine structure of navigation signals. With this expression, we can optimize the Gabor Bandwidth of the signal, and find out the corresponding MCS vector and chip waveform, so as to get higher range accuracy. The method in this paper, in theory, is of great value in the design of next-generation navigation signals. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg. Source

Zhang T.-Q.,Tsinghua University | Zhang T.-Q.,Beijing Global Information Center | Wang Y.,Tsinghua University | Cui X.-W.,Tsinghua University | Lu M.-Q.,Tsinghua University
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics

In order to improve the anti-jamming performance in global navigation satellite system (GNSS) receivers, an improved anti-jamming technique based on frequency-spectrum amplitude domain processing (FADP) filter is proposed, which is more robust. Firstly, an overlap windowed fast Fourier transform (FFT) is used to relieve the spectrum leakage. Then, according to the analysis of the differences between the statistical characteristics of the time-domain waveform and spectrum data, a new mathematical function of amplitude domain processing (ADP) is designed. Meanwhile, a simplification of the procedures save the computation resources in some way. Finally, based on the GPS software receiver platform, experiments comparing the improved FADP with the original FADP verify that the improved method has stronger suppression ability and smaller insertion loss than the orginal one on non-Gaussian interference. Source

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