763记录受地电测数干扰原因及其排除方法

７６３记录受地电测数干扰原因及其排除方法陆永义，李少云，许国娥，闫素平（中国安徽省２３００３１合肥地震台）郑志坤，史升大（中国安徽省２３００３１合肥地震局）合肥地震台７６３记录受地电干扰非常严重，特别是地面潮湿时更为突出。干扰幅度最大时达到２０ｍｍ（...

相继干扰消除的无线网络中的调度算法

相继干扰消除(successive interference cancellation,简称SIC)是一种多包接收技术,它从冲突信号中解码报文.SIC可有效减轻无线网络中的干扰.SIC的顺序解码特性给链路调度带来了新的挑战.提出并发图以刻画SIC导致的链路相关性.基于并发图,定义链路的干扰数并据此设计有效的调度机制.证明了基于并发图的链路调度是NP-hard的,而最大干扰数提供了极大贪婪算法的性能下界.在讨论了一类基于独立集的贪婪算法之后,结合干扰数对链路排序,给出了一种理论上性能更好的算法.仿真结果表明,仅需略高于现有模型的开销,与IEEE 802.11相比,新调度算法的性能提高可达110%.

对SAR的方位向间歇采样转发干扰

立足于干扰机天线收发分时体制,研究了方位向间歇采样转发干扰方法。其核心思想是对SAR发射的脉冲串信号进行间歇采样和存储,再经一定处理后恢复为模拟信号在下一个或数个脉冲重复周期转发出去形成干扰,然后利用SAR方位向匹配滤波特性,就可以形成方位向多假目标欺骗的效果,避开了高速采样和同时收发高度隔离的难题。理论分析了方位向间歇采样转发干扰的原理和干扰效果,指出了间歇采样周期、占空比及干扰组数等关键参数对干扰效果的影响,通过仿真实验进行了验证。研究结果表明,方位向间歇采样转发干扰是种有效的、易于工程实现的干扰样式。

无线Mesh网络中基于链路层最优信道分配策略研究

无线Mesh网络技术具有通信地点任意性与实时性的特点,可以方便地扩大校园网覆盖范围。随着网络用户和业务多元化的推进,如何提高无线Mesh网络吞吐量和合理分配信道是多信道无线Mesh网络技术的关键。文章基于对现有信道分配方案的优点和方案制约的分析,提出一种链路层最优信道分配方案,并通过仿真实验进行验证。

Narrowband interference suppression in TR-UWB system based on cognitive radio theory

A cognitive radio transmitted reference ultra-wideband（CR-TR-UWB） system is proposed to improve the performance of TR-UWB systems with narrowband interference（NBI） from primary users（PU）.The transmitter of the CR-TR-UWB system detects the band of PU,and then sends prolate spheroidal wave functions（PSWF） pulses with the same limited band as PU＇s to reduce interference with PU.The receiver uses a notch filter before autocorrelation to eliminate NBI from PU.The simulation results show that the bit error rate（BER） performance of the CR-TR-UWB system is close to that of TR-UWB systems without NBI when the system is interfered by single or double NBIs with a signal to interference ratio（SIR） of 0 dB,and if the signal to noise ratio（SNR） is 10 dB and the SIR varies from-20 to 10 dB,BER performance varies no more than an order of magnitude.The system has excellent resistance to NBI,strong robustness BER performance at different SNRs,and smaller interference with the same frequency band PU.

Orthogonal experiment design of EMI of security monitoring system in coal mines

Security monitoring system of coal mines is indispensable to ensure the safe and efficient production of colliery. Due to the special and narrow underground field of the coal mine, the electromagnetic interference can cause a series of misstatements and false positives on the monitoring system, which will severely hamper the safe production of coal industry. In this paper, first, the frequency characteristics of the interference source on the power line are extracted when equipment runs normally. Then the finite difference time domain method is introduced to analyze the effects of the electromagnetic interference parameters on the security monitoring signal line. And the interference voltage of the two terminal sides on the single line is taken as evaluating indexes. Finally, the electromagnetic interference parameters are optimized by orthogonal experimental design based on the MATLAB simulation on the normal operation of equipment.

Simulation of Dynamic Electromagnetic Interference Environment for Unmanned Aerial Vehicle Data Link

In order to test the anti-interference ability of an Unmanned Aerial Vehicle(UAV) data link in a complex electromagnetic environment,a method for simulating the dynamic electromagnetic interference of an indoor wireless environment is proposed.This method can estimate the relational degree between the actual face of an UAV data link in an interface environment and the simulation scenarios in an anechoic chamber by using the Grey Relational Analysis(GRA) theory.The dynamic drive of the microwave instrument produces a real-time corresponding interference signal and realises scene mapping.The experimental results show that the maximal correlation between the interference signal in the real scene and the angular domain of the radiation antenna in the anechoic chamber is 0.959 3.Further,the relational degree of the Signal-toInterference Ratio(SIR) of the UAV at its reception terminal indoors and in the anechoic chamber is 0.996 8,and the time of instrument drive is only approximately 10 μs.All of the above illustrates that this method can achieve a simulation close to a real field dynamic electromagnetic interference signal of an indoor UAV data link.

A COMPARISON OF SOME ELECTRONIC COUNTERMEASURES ON INVERSE SYNTHETIC APERTURE RADAR (ISAR)

Inverse Synthetic Aperture Radar (ISAR) is an important means for target classification, recognition, identification and many other military applications. A simulation model of ISAR system is established after analyzing the principle of ISAR imaging, and then several ECM (Electronic Counter Measurement) techniques are studied. Simulation experiments are done on the basis of such research. The experimental result of the research can be used for ECM equipment.

A New Chaotic Parameters Disturbance Annealing Neural Network for Solving Global Optimization Problems

Since there were few chaotic neural networks applicable to the global optimization, in this paper, we propose a new neural network model ? chaotic parameters disturbance annealing (CPDA) network, which is superior to other existing neural networks, genetic algorithms, and simulated annealing algorithms in global optimization. In the present CPDA network, we add some chaotic parameters in the energy function, which make the Hopfield neural network escape from the attraction of a local minimal solution and with the parameter annealing, our model will converge to the global optimal solutions quickly and steadily. The converge ability and other characters are also analyzed in this paper. The benchmark examples show the present CPDA neural network's merits in nonlinear global optimization.

Disturbance observer based position tracking of electro-hydraulic actuator

A nonlinear controller based on an extended second-order disturbance observer is presented to track desired position for an electro-hydraulic single-rod actuator in the presence of both external disturbances and parameter uncertainties. The proposed extended second-order disturbance observer deals with not only the external perturbations, but also parameter uncertainties which are commonly regarded as lumped disturbances in previous researches. Besides, the outer position tracking loop is designed with cylinder load pressure as output; and the inner pressure control loop provides the hydraulic actuator the characteristic of a force generator. The stability of the closed-loop system is provided based on Lyapunov theory. The performance of the controller is verified through simulations and experiments. The results demonstrate that the proposed nonlinear position tracking controller, together with the extended second-order disturbance observer, gives an excellent tracking performance in the presence of parameter uncertainties and external disturbance.

A Linear Interference Cancellation Multi-User Detector for Synchronous CDMA Communications

This paper describes a linear interference cancellation multi user detector for synchronous DS CDMA systems under the condition that all spread spectrum code waveforms have the constant cross correlating coefficients. The basic idea is to get the estimation for total multiple access interference (MAI) of all users using a reference code waveform, then subtract the total MAI from the received signal. The structure of such a detector is nearly similar to the conventional detector. The BER expression obtained in the paper shows significant performance improvement compared to the other detectors.

Adaptive Soft Frequency Reuse Scheme for In-building Dense Femtocell Networks

Femtocell networks have emerged as a key technology in residential, office building or hotspot deployments that can sig- nificantly fulfill high data demands in order to offioad indoor traffic from outdoor macro cells. However, as one of the major challenges, inter-femtocell interference gets worse in 3D in-building scenarios because of the presence of numerous interfering sources and then needs to be considered in the early network planning phase. The indoor network planning and optimization tool suite, Ranplan Small- cell~, makes accurate prediction of indoor wireless RF signal propagation possible to guide actual indoor femtocell deployments. In this paper, a new adaptive soft frequency reuse scheme in the dense femtocell networks is proposed, where multiple dense femtocells are classified into a number of groups according to the dominant interference strength to others, then the minimum subchannels with different frequency reuse factors for these groups are determined and transmit powers of the group- ing sub-channels are adaptively adjusted based on the strength to mitigate the mutual inter- ference. Simulation results show the proposed scheme yields great performance gains in terms of the spectrum efficiency relative to the legacy soft frequency reuse and universal fre- quency reuse.

Improving Reliability of Communication in RS-485 Design

Three aspects of RS 485 application, which affect the reliability of communication of data system are analyzed and discussed. In network configuration, it presents the optimal configuration for the bus of RS 485, the better rule for derivative line and the choice for termination. In hardware design, it presents three parts of driver’s peripheral circuit. In control software design, it presents a method of using 75176’s DE line to control the driver.

Golay Sequence Based Time-Domain Compensation of Frequency-Dependent I/Q Imbalance

A time-domain frequencydependent I/Q imbalance compensation scheme based on Golay complementary sequence for receiver is presented. By utilizing property of Golay sequence, the signal and its conjugate interference(image interference)in preamble are separated by correlation and used to estimate I/Q imbalance parameters.After that, a Least Square(LS) estimation of compensation filter is obtained and adopted in the compensation structure. Two applications of the presented algorithm are discussed: we could either estimate the channel along with I/Q imbalance or estimate the imbalance parameter only to maintain a lower cost. Both applications are testified by simulation. The results show that the image interference is significantly suppressed even in poor SNR condition, and the computation cost of the algorithms is low.

Chip-level space-time equalization receiver scheme for MIMO HSDPA systems

A chip-level space-time equalization receiver scheme is proposed for multiple-input multiple-output high-speed downlink packet access (MIMO HSDPA) systems to jointly combat the co-channel interference and the inter-code interference. A fractional sample equalizer is also derived to further improve the performance of the receiver. Performance analysis and the calculation of the output signal to interference ratio (SINR) at each receiver antenna are presented to help direct the design of equalization weight in a more optimal manner. System simulations demonstrate the significant performance gain over conventional Rake receiver and high potential of MIMO HSDPA for high-data-rate packet transmission.

INTERFERENCE MITIGATING BASED ON FRACTIONAL FOURIER TRANSFORM IN TRANSFORM DOMAIN COMMUNICATION SYSTEM

The method of FRactional Fourier Transform (FRFT) is introduced to Transform Domain Communication System (TDCS) for signal transforming in the paper after theoretical analysis. The method yields optimal Basis Function (BF) by FRFT with optimal transform angle. The TDCS using the proposed method has wider usable spectrum, stronger robustness and better ability of anti non-stationary jamming than using usual methods, such as Fourier Transform (FT), Auto Regressive (AR), Wavelet Transform (WT), etc. The main simulation results are as follows. First, the Bit Error Rate (BER) Pb is close to theoretical bound of no jamming no matter in single tone or in linear chirp interference. Second, the interference-to-signal ratio J /E is at least 12dB more than that of Direct Spread Spectrum System (DSSS) under the same BER if the spectrum hopping-to-signal ratio is 1:20 in chirp plus hopping interfering. Third, the Eb /N 0(when estimation difference is 90% between trans- mitter and receiver) is about 3.5dB or about 0.5dB (when estimation difference is 10% between transmitter and receiver) more than that of theoretical result when no estimation difference un-der Pb=10-2.

Robust stabilization and disturbance attenuation for a class of underactuated mechanical systems

The robust control problem for a class of underactuated mechanical systems called acrobots is addressed. The goal is to drive the acrobots away from the straight-down position and balance them at the straight-up unstable equilibrium position in the presence of parametric uncertainties and external disturbance. First, in the swing-up area, it is shown that the time derivative of energy is independent of the parameter uncertainties, but exogenous disturbance may destroy the characteristic of increase in mechanical energy. So, a swing-up controller with compensator is designed to suppress the influence of the disturbance. Then, in the attractive area, the control problem is formulated into a H~ control framework by introducing a proper error signal, and a sufficient condition of the existence of Hoo state feedback control law based on linear matrix inequality （LMI） is proposed to guarantee the quadratic stability of the control system. Finally, the simulation results show that the proposed control approach can simultaneously handle a maximum ±10% parameter perturbation and a big disturbance simultaneously.

Research on Influence of Electromagnetic Interference on X-Ray Digital Detection

X-ray digital imaging technology has found wide application owing to its advantages of real-time, visualization and rapid imaging. In substations the substantial electromagnetic interference has some influence on the live detection by the X-ray digital imaging technology, hindering the promotion of the technology in the detection of electric equipment. Based on a large number of field tests, the author carded out a series of researches on electromagnetic interference protection measures, image de-noising, and image enhancement algorithms.

A Perturbing Scheme of Digital Chaos

With finite computation precision, digital chaos will lose chaotic characteristic. An efficient perturbance-based algorithm perturbing chaos variable algorithm(PCV) was proposed, which can be regarded as a remedy to digital chaos. After being perturbed, digital chaos systems are able to generate pseudo random sequences with perfect statistical properties and can be used as key stream generators in cryptogram.

On Multi-Frequency Channel Interference Alignment of 3 Channels and 4 Users

This paper explores the multi-frequency independent channel interference alignment(MFC-IA) system of 3 channels and4 users,and single data stream transmit,i.e.(3×3,1)~4 system.We derive the analytic solution for(3×3,1)~4 MFC-IA system.Based on the analytic solution,an optimization problem is proposed aim at the optimal IA solution.Then based on such a math model,we propose a simulated annealing(SA) algorithm to search optimal IA solution.The simulation results show that the simulated annealing IA algorithm has a better sum rate performance than iterative maximize signal to interference plus noise ratio(Max-SINR) algorithm.This result can be extended to single data stream multi-antenna IA system with 3 antennas and4 users.