Advanced Materials Research Vols. 846-847

Abstract: With the wide application of electronic technology, electromagnetic interference has become one of the main factors to weaken electronic system performance. In communication technology and equipment, it is the development of light-duty design, low cost, high quality electronic components and electronic system that is the main object of this study. Radio frequency MEMS devices are low energy consumption, good stability. Therefore it has a strong competitiveness in the communications electronics. But EMI electromagnetic interference problem has increasingly become prominent, and based on this, this paper makes a further study on the main electromagnetic interference electromagnetic radiation of MEMS devices. In addition, this paper also establishes the mathematical model of electromagnetic radiation. Finally this paper makes an analysis and study on the shielding effect of MEMS antenna under certain magnetic materials. Through the simulation research, it is obtained that the electromagnetic effect of electronic system MEMS is good and its highest performance is more than 60 db. Whats more, shielding materials are within the range of 15 to 20 GHZ, whose shielding effects reach the maximum. The largest is close to 80 db.

Abstract: Improving network control system---NCS reliability and safety has important practical significance because NCS is a hot research subject in these years. Fault diagnosis methods are researched in this paper according to NCS with long-time delay and data packet loss. Firstly, given a NCS with long-time delay, a state observer is structured. Secondly, make the state estimation error equation equivalent to an asynchronous dynamical system having event incidence constraint according to whether the system having data packets loss. The problem of fault diagnosis is converted to filtering problem through structuring filtering residual system based on the observer, then giving a corresponding filter designing algorithm. The designed fault diagnosis filter system not only make sure the stability of the closed loop system but also make the residual systems norm less than given reduction level. Finally, the simulation results prove that the algorithm can diagnose faults effectively.

Abstract: This paper constructs a sliding mode observer of fixed long delay network control system with an augmented modeling method, and then proves the feasibility of system residuals converging to zero by Lyapunov stability theorem. The network control system fault diagnosis is discussed in depth by detecting changes in the residuals. In addition, this paper takes Gradient faults and mutation faults of actuator as examples to conduct fault diagnosis simulation, and the simulation results show that this method can detect the system faults effectively.

Abstract: Most of the electroencephalograph (EEG) acquisition systems use group of high precision electrical signal amplifier to record and analysis. But the huge input circuit and testing time is difficult to application for portable devices. In this paper, a new design of portable EEG signal acquisition system is designed. This paper presents an effective chip (ADS1299) implementation of an eight-channel EEG signal acquisition. Compared with the existing system, this design greatly simplifies the front-end circuits and improves the common mode rejection ratio (CMRR). The system has the features of high integration density, good flexibility and practicability. It is in line with the development trend of modern EEG, and meets the new requirements of modern EEG.

Abstract: Global Navigation Satellite System (GNSS) interoperability could make use of the information from different navigation satellite systems. To estimate GNSS interoperability at the system level, an innovative assessment algorithm was presented in this paper. First of all, three assessment parameters, namely, Dilution Of Precision (DOP), Navigation Satellite System Precision (NSSP) and Navigation Satellite System Integrity (NSSI) were introduced. Secondly, availability and continuity of the assessment parameters were adopted to quantify the GNSS performance. A further step was then taken to focus on the assessment rule for GNSS performance by employing the weighted sum of availability and continuity. Simulation results demonstrate that GNSS performance could be improved significantly by interoperability.

Abstract: When detecting low-attitude targets, the angular accuracy of the meter-wave radar will descend because of the multipath reflecting from ground. Since multipath signals can be regarded as multipath jamming coming from the mainlobe, we propose an angle measurement based on the mainlobe multipath jamming suppression through differential constraints technique. The weight of the new approach is obtained through certain constraints on the sum-difference beams, which can suppress the jamming and keep the curve of the monopulse ratio unchanged simultaneously. Then form sum-difference beams and calculate the ratio of the monopulse ratio of the target. Finally, obtain the angle of the target through the determination of the smallest difference between the monopulse ratio of the target and the quiescent monopulse ratio. The method proposed in this paper can preserve good precision of the measurement angle. The result is verified by computer simulation.

Abstract: In traditional frequency synthesizers, there is a frequency synthesis module for every output channel, so there is crosstalk between output channels. The more the output modules, the more is the crosstalk. Deeply researching shows that the crosstalk between output modules has most of the influence on output stray [2,. To improve the output stray, a new scheme of designing frequency synthesizer with low output stray is given in this paper. In the new scheme, there is only one frequency synthesis module for all outputs. The output of the module is divided into several outputs by the power divider. Then these outputs directly input to the output modules. In this way, the crosstalk between the frequency synthesis modules can be effectively avoided, and the output stray can be significantly reduced. On the other hand, the volume and the cost of the synthesizer is reduced. Simulation result shows that the new scheme can meet the requirements of low output stray.

Abstract: Now some special circuits need higher precision in relatively fixed range. While the precision of a common digital-to-analog converter (DAC) is equidistant, which means the higher the precision is, the greater the number of bits. The increase of number of bits will slow down the speed of converter. This architecture we present here aims at finding a way of solving the problem. It uses M bits of the N-bit DAC to adjust precision by changing the current of the voltage division circuit, which alters the range of the DAC to a certain extent.

Abstract: The chirp signal can bring some useful information for structural non-destructive evaluation (NDE) applications due to its broad frequency components with different sensitivity to defects that exist in test pieces. This paper introduces a defect imaging method based on the chirp signal. When a chirp signal is used as excitation in the guided wave detection system, tone burst results can be gotten from the response easily. Numerical simulation results show that this method simplifies the procedure to find the best exciting frequency and guided wave mode for the hole defect detection, and yields more accurate defect imaging results with arc imaging algorithm.

Abstract: As the accelerated development of the existing mobile communications and Internet integration, high-speed mobile access and Internet Protocol-based service become mature for different kinds of applications, which provide a great convenience for the remote wireless monitoring, mobile data transmission and so on. In this paper, an environmental monitoring data transmission system based on 3G networks is designed to transmit environmental data which is collected through sensors to server-side. The data transmission system is functioning with remote data transmission, and monitoring data reviewing at remote terminal any time. Scientific monitoring data can accurately, timely and comprehensively reflect of the various environmental parameters on-site detection status. The system components of environment monitoring platform based on virtual instrument is introduced firstly. Then, the network transmission system scheme based on Socket communication is proposed. Finally, the data transmission between LabVIEW application of monitoring terminal and PHP application of server-side through Socket interface is achieved. This system transmits well, and queries conveniently. It is safe and timely while being applied in environmental monitoring data transmission.