Yanxin Li

The latest design and development of the field mill used as atmospheric electric field sensor

In this paper, the sensor of a traditional atmospheric electric field mill was optimized. The earthing brush and photoelectricity synchrodetector were removed. A stator with double-electrode difference structure was adopted to produce difference. It was put in a signal acquisition and processing printed circuit board directly. The commutating pulsant signal of DC motor current was synchronously acquired to detect the phase of the rotor, which realized the identification of electric field polarity. Based on this, a novel three-dimensional electric field sensor was designed, and it was able to identify the polarity of the three dimensions at the same time, and the feasibility was proved by calculation and reasoning.

TGR analysis of a kind of grounding electrode

This paper discussed the transient Grounding Resistance(TGR) of a kind of simple earthing electrode. In order to study the influence of TGR, a kind of TGR testing system is adopted, which is testing the TGR under impulse current. In this paper, the round steel are utilized as the material of the earthing electrode. In addition, the TGR is calculated using FDTD method. The waveform and results of calculated with FDTD is similar to the measured results. Therefore, the accurry of the experimental system is proved. The experimental results have practical value in the project.

Study of EMP effects experiment on the solid state relay

An experiment of EMP effects on the solid state relay is described. In order to get the radiation interference threshold value of the relay, the length of the connection is cut as short as possible. The radiation interference threshold value is found to be superior to 75kV/m. By using capacitor coupling, the conduction interference voltage threshold value 3850V is found. The experiment results also show that the EMP interference at the input port of the relay can induce transient switching on, which can cause misworking.

Test of the lightning indirect effects on an aircraft

With the development of electronics and materials, the requirements of aircraft lightning protection ability increasingly improved. In this paper, a scale model of a helicopter as a test object, the lightning indirect effects test method is described and studied in detail. Two kinds of the circuit conductor arrangements are designed. The electric and magnetic field values of the nose, middle and the tail of the helicopter in each arrangement are measured to obtain the pulse waveforms and the peak value data. Finally, the regularities of the electric and magnetic fields distribution are summarized and the peak data are evaluated.

A test system on antenna effect analysis under lightning strikes

A test system applied to analyze lightning effect on aircraft antenna is proposed. The designed system is made up of the lightning surge generator, arc discharge rod, antenna to be tested, aluminum shield, water resistance voltage divider, portable digital oscilloscope and network analyzers. In the measurement, the tested antenna is mounted on the top of the aluminous experimental box. The lightning current is directly or indirectly injected into the antenna through the arc discharge rod. Moreover, the load resistor of 50Ω is at the terminal, and the water resistance voltage divider that carries the residual lightning current is connected with a digital oscilloscope. The experimental results indicate that the proposed system with good reliability and anti-interference ability is simple, which is also demonstrated to be applicable for performing antenna Lightning effect analysis.

A small size dipole E-field sensor for calibration of field distribution in EMP simulator

The calibration of field distribution in EMP simulator is discussed. A small size dipole sensor with built-in optic transmitter and fiber optic output connection is designed to measure field distribution in various points of the EMP simulator. Influence of the dipole sensor to the field distribution is first analyzed by numerical simulation and the actual field distribution is measured by the dipole. A correction coefficient is proposed based on the measurement results. The available working space in EMP simulator for sensor calibration is also defined.

A Compact High Power Pulsed field generator with fast rising-time

Shielding effectiveness test is a typical application of nanosecond high voltage pulse. A Compact High Power Pulsed Simulator for the shielding effectiveness is developed. To obtain fast rise time of pulse voltage, a switch has to have low inductance. A liquid gap switch has this property. This switch operates with fixed anode, cathode and a removable trigger electrode. The switch gap is filled with innocuous, fully biodegradable, and well insulating refined rap oil. By using the liquid gap switch, the voltage rise time is obtained approximately 1.8 ns and the peak value of the pulse electric field radiated by the simulator is more than 9 kV/m at 0.6 m in front of the antenna. Experimental results show that the best linear characteristics of peak value of the output voltage and maximum amplitude of the electric field.

Influence of HEMP electromagnetic distribution on various plasma

Plasma is conductor and dispersive medium. It can shield electromagnetic field. Plasma has a remarkable feature: its medium parameters are changeable with frequency. In this paper, the Frequency-Dependent Finite-Difference Time-Domain ((FD)2TD) method is used to model electromagnetic reflection and transmission. First efficiency of SO-FDTD is verified. Then electromagnetic reflection and transmission characteristic is analyzed when plasma parameters change.

Neural network and antenna model application on pulse magnetic field measurement

Introduces a pulse magnetic field measurement system which is used in strong electromagnetic environment. A small loop antenna is used as pulse magnetic field sensor and a wide band analog fiber transmission device is used to transmit the signal. The system uses BP neural network to calibrate the nonlinearity of the fiber transmission device and uses the model of the antenna to recover the pulse magnetic field. Using Matlab function to realize the system method can simplify the program. An experiment result shows that the system is suitable for measuring wide band pulse magnetic field.

Analysis of electromagnetic pulse field distribution of effective work space of GTEM cell

This paper introduces the structure of gigahertz TEM cell (GTEM cell). And the Finite-Difference Time-Domain (FDTD) method is used to model electromagnetic field of effective work space of GTEM cell accurately. The effect of meauring system put at the effective work space is also analyzed. This work will offer theory direction of electromagnetic field distribution of effective work space of GTEM cell.