In this paper, chaos sequence is used to replace the traditional spread spectrum sequence. From the perspective of the communication partner, a new method of generating the initial value of chaotic ...sequence is proposed, which is more suitable for the multi-base spread spectrum system and easy to extract. In order to further improve the error performance of the system and ensure the integrity of the system, an improved suboptimal soft information extraction method based on log-likelihood ratio (LLR) is proposed in the channel coding module, which can further improve the error performance of the system. On this basis, we choose the synchronization mode of multiple transmission of one reference signal to solve the problem that chaotic sequence is difficult to obtain synchronization because of its aperiodic characteristics. Finally, the system is simulated in the channel with low SNR. The simulation results show that chaotic sequence as spread spectrum code can make the signal transmit accurately in the worse channel environment. The performance gain of applying soft information decoding decision in the multibase spread spectrum system with chaotic sequence as spread spectrum code can reach 5.2 dB compared with the traditional direct spread spectrum system.
Article Highlights
An iterative generation algorithm for chaotic sequences is proposed to simplify the system scale.
The chaotic sequence is combined with the M-ary spread spectrum system to improve the anti-interception capability.
Combine soft information decoding with M-ary spread spectrum to improve the anti-interference ability of the system.
Abstract
For the problems of complicated work content and error-prone workload of secondary circuits, a three-dimensional visualization method is proposed for the visualization and management of the ...physical circuits of the control and protection system of the converter station based on digital twin technology. The system can be used to improve the work efficiency of operation and maintenance personnel by constructing a secondary circuit information data model, generating corresponding data through artificial intelligence image recognition and manual review of secondary circuit drawings and schematics, and performing accurate corresponding circuit data analysis and 3D visualization management of the secondary physical circuits of control and security equipment, which can visualize the circuit information of control and security equipment in the station from outside to inside at multiple levels and multiple dimensions.
A wideband integrated antenna is proposed with realization of radiation and dual polarized absorption in same frequency band. The novelty of the proposed integrated structure lies in the ...share-aperture of frequency-selective absorber and magnetoelectric dipole, which remain mutually independent and orthogonal operating characteristics. In the share-structure, each array element can be selectively connected to an excitation port or a resistor loading (50 Ω) to re-use the antenna port impedance for receiving and absorbing co-polarized waves. While the cross-polarized waves are reflected by antenna ground and absorbed by mounted resistors on the symmetric patches at the top layer of the antenna array. Consequently, the proposed antenna exhibits both wideband radiation and dual polarized absorption simultaneously with low profile (0.22λ0). Finally, a prototype 2×2 antenna array is fabricated and measured, demonstrating an impedance bandwidth of 92.7% for |S11| < −10 dB from 2.2 to 6 GHz. Moreover, the proposed antenna has 10 dB RCS reduction bandwidth of 100% (2-6 GHz) for x- and y-polarized normally incident waves.
Metamaterials Liu, Ruopeng; Cui, Tie Jun; Smith, David R
2010, 2009, 20091005, 2009-11-15
eBook
Metamaterials:Theory, Design, and Applications goes beyond left-handed materials (LHM) or negative index materials (NIM) and focuses on recent research activity. Included here is an introduction to ...optical transformation theory, revealing invisible cloaks, EM concentrators, beam splitters, and new-type antennas, a presentation of general theory on artificial metamaterials composed of periodic structures, coverage of a new rapid design method for inhomogeneous metamaterials, which makes it easier to design a cloak, and new developments including but not limited to experimental verification of invisible cloaks, FDTD simulations of invisible cloaks, the microwave and RF applications of metamaterials, sub-wavelength imaging using anisotropic metamaterials, dynamical metamaterial systems, photonic metamaterials, and magnetic plasmon effects of metamaterials. TOC:Preface.- Acknowledgments.- Table of Contents.- List of Contributors.- Introduction to Metamaterials.- Optical Transformation Theory.- General Theory on Artificial Metamaterials.- Rapid Design of Metamaterials.- Broadband and Low-Loss Non-Resonant Metamaterials.- Experiment on Cloaking Devices.- Finite-Difference Time-Domain Modeling of Electromagnetic Cloaks.- Compensated Anisotropic Metamaterials: Manipulating Sub-Wavelength Images.- The Dynamical Study of Metamaterial Systems.- Photonic Metamaterials Based on Fractal Geometry.- Magnetic Plasmon Modes Introduced by the Coupling Effect in Metamaterials.- Enhancing Optical Coupling with Metamaterials.- Wideband and Low Loss Metamaterials for Microwave and RF Applications: Fast Algorithm and Antenna Design.- Experiments and Applications of Metamaterials in Microwave Regime.- Left-handed Transmission Line of Low Pass and Its Applications.- Glossary.- Index.
The transmission line, as the faultiest device in power system, cross many complex areas which will cause worse work condition. This is, both the rate of faulty and the difficulty of the manual fault ...location are raised. While accurate fault location method could reduce the workload and outage cost, increase the speed of repairing and improve both the reliability and economics of power system. Therefore, it is essential for HVDC systems which have much longer transmission lines. The existing fault location device of HVDC transmission lines are based on the principle of transient travelling-wave. However, due to the interference caused by on-off of power electronic devices and signal resonances, the single-ended travelling-wave method can not be applied in HVDC. The characteristics of clutter interferences of HVDC system and the coupling between double pole lines are analyzed in paper. A novel single-ended travelling-wave fault location method for HVDC transmission lines based on the correlation between two pole lines is proposed. The signal of the non-fault pole line is applied as reference signal; the method suppresses interference through the cross-correlation calculation between the fault and the no-fault pole line. So the reflected wave is enhanced and the identification reliability of the reflected wave is improved. The validity of the method is verified by simulation and on-site data analysis.
The design of the communication system follows the Nyquist intersymbol interference (ISI) criterion, which explains the design principle of the transmitting and receiving filters to mitigate the ...effects of ISI. In this work, we study how to utilize the ISI to benefit a communication system. We propose a novel modulation framework, which transmits the constellation symbols much faster than the Nyquist rate and therefore introduces heavy interference between consecutive symbols. The benefit of such modulation is that the frequency bandwidth of the modulated symbols is significantly compressed compared to the traditional modulated symbol with the same symbol rate. We discuss the demodulation process and present a particle filtering-type approximation demodulation method. Numerical simulation and comparison study demonstrate that under an achievable signal noise ration condition the meta-modulation realize a high spectrum efficiency, which is impossible to implement in the traditional QAM system.
Multiple-cylinder scattering of electromagnetic plane waves are considered. It is shown that the process can led to formation of two kinds of high intensity areas of electromagnetic waves. The first ...type arise inside cylinder due to so-called whispering gallery modes (WGM), while the second type represents itself a narrow, high-intensity beam of light generated at the shadow-side surface of illuminated dielectric cylinders. In our model, WGM can occur because of the presence of additional cylinder scatterers at specific location, while WGMs can only form in a single cylinder for specific cylinder radius and/or wavelength values. Also, presence of the additional cylinders increases a length of photonic nanojets (up to two times) compared to the case of a single cylinder. The results of calculation for different values of electric permittivity and radii of cylinders are presented and discussed.
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