Research on the Calculation Method of Electrostatic Field of a Thunderstorm Cloud

The electrostatic field in the space excited by a thunderstorm cloud reflects the trend of the spatial potential and has a great influence on the selection of lightning discharge paths. Some studies have used an approximate method to calculate the electrostatic field excited by a thunderstorm cloud, but the error is still relatively large. In order to improve the computational accuracy, the second-order approximate solution of the electric field is obtained in this paper by using a binomial expansion of the complex quantized function, discarding the higher-order small terms and integrating the main term according to the convergence of the function. The first-order approximate solution and the second-order approximate solution are used to calculate the electrostatic field excited by a thunderstorm cloud using the same version of MATLAB on the same configuration of computers. By comparison, it is found that the computation time using the two approximate solutions is not much different, but the error between the second-order approximate solution and the exact solution is significantly smaller than that between the first-order approximate solution and the exact solution. It is shown that using the second-order approximate solution to calculate the electrostatic field of a thunderstorm cloud can greatly improve the computational accuracy without sacrificing the computational efficiency, which is of great significance for the accurate warning when lightning is approaching

Study on coupling effect between lightning electromagnetic field and unshielded multi-core cable

In order to investigate the terminating load voltage of the unshielded multi-core cable coupled with lightning electromagnetic pulse(LEMP), we simulate LEMP within the bounded-wave transmission line which is input with a lightning surge signal produced by WU-800-type MARX generator and conduct the relevant experiments towards multi-core cable lines radiated by LEMP. We can get the respond laws of induced voltage of the load by changing the length of unshielded multi-core cable, angles between LEMP and cable, waveforms of LEMP as well as cable terminal loads including linear and non-linear loads. Results show that the amplitude of induced voltage is mainly determined by rising part of electromagnetic field waveforms and the pulse width has little effect on the induced voltage. The respond amplitude and the respond frequency are obviously affected by the length of cable. The polarization direction of the electric field has a great impact on the amplitude of terminal response, but it does not change the waveforms of the induced voltage. With the termination of test side increasing, the induced voltage is gradually increased, but the load in the other side has no effect on the induced voltage

Unshielded Two-Wire Circuit Systems under Weak Unbalance for High-Intensity Radiated Field Radiated Susceptibility by Double Bulk Current Injection

In unshielded two-wire circuits of weapon systems, the equipment at both ends of the cable needs to be tested at the same time. The theoretical model of substituting double bulk current injection (DBCI) for high-intensity radiated field (HIRF) electromagnetic radiation is established, which aims to calculate the relationship between the injection excitation voltage source and the radiation field intensity. Additionally, the conditions required for linear extrapolation is clarified. Subsequently, the test method of using DBCI for the HIRF radiated susceptibility (RS) is proposed. Next, the verification of the CST studio and the pass-through load test are performed. All results shows that the test method can avoid the influence of the impedance parameters of the two equipment at both ends, which can be applied to nonlinear terminals for the HIRF RS test

Study on the Law and Mechanism of the Third-Order Intermodulation False Alarm Effect of the Stepped Frequency Ranging Radar

In order to improve the radar’s electromagnetic protection ability, it is essential to master the law of the false alarm effect of the radar’s out-of-band third-order intermodulation electromagnetic radiation, starting from the circuit field-circuit coupling mechanism, and the mechanism of the third-order intermodulation false alarm effect is analyzed. Taking a stepped frequency ranging radar as the research object, the absolute level value of the false alarm signal is selected as the sensitive criterion of the false alarm effect. The dual-frequency electromagnetic false alarm interference effect is carried out by using the method of the differential mode injection equivalent substitution electromagnetic radiation. The results show that the dual-frequency electromagnetic interference will cause the radar to generate the third-order intermodulation false alarm signal with the random position and waveform spreading. Under a certain interference intensity, the level of the third-order intermodulation false alarm signal increases with the increase of the interference field strength. With the continuous increase of the interference field strength, the fifth-order intermodulation false alarm signal gradually appears. The imaging mechanism, the waveform characteristics, and the level change law of the fifth-order intermodulation false alarm target, are similar to the third-order intermodulation false alarm target, and its position is also random. The maximum third-order intermodulation false alarm signal can reach 18 dBmV, indicating that the radar is sensitive to the out-of-band intermodulation electromagnetic interference

Feasibility and Error Analysis of Using Fiber Optic Temperature Measurement Device to Evaluate the Electromagnetic Safety of Hot Bridge Wire EEDs

Most studies assessing the safety of hot bridge wire EEDs employ temperature sensors that directly use the measurements of the temperature measurement device without analyzing the accuracy of the temperature measurement. This study establishes the response function of the exposed bridge and exposed bridge temperature rise system of hot bridge wire EEDs through the Rosenthal’s temperature rise equation and Laplace transformation as well as experimental tests, and through the response function, the response law and numerical characteristics of the two are compared and analyzed under four typical excitations. Under steady current injection and continuous-wave radiation, both exposed bridge and exposed bridge temperature measurement systems can reach thermal equilibrium, and the equilibrium temperature of both are the same. However, under pulse excitation, the temperature rise measurement value is significantly different from the actual value due to the large difference in response time of the exposed bridge (1 ms) and the exposed bridge temperature measurement device (0.82 s). Studies have shown that under steady current injection and continuous-wave radiation, temperature rise measurements can be directly applied to the safety assessment of hot bridge wire EEDs, while under pulsed conditions, temperature rise measurements cannot be directly applied

Study on the Law and Mechanism of the Third-Order Intermodulation False Alarm Effect of the Stepped Frequency Ranging Radar

In order to improve the radar’s electromagnetic protection ability, it is essential to master the law of the false alarm effect of the radar’s out-of-band third-order intermodulation electromagnetic radiation, starting from the circuit field-circuit coupling mechanism, and the mechanism of the third-order intermodulation false alarm effect is analyzed. Taking a stepped frequency ranging radar as the research object, the absolute level value of the false alarm signal is selected as the sensitive criterion of the false alarm effect. The dual-frequency electromagnetic false alarm interference effect is carried out by using the method of the differential mode injection equivalent substitution electromagnetic radiation. The results show that the dual-frequency electromagnetic interference will cause the radar to generate the third-order intermodulation false alarm signal with the random position and waveform spreading. Under a certain interference intensity, the level of the third-order intermodulation false alarm signal increases with the increase of the interference field strength. With the continuous increase of the interference field strength, the fifth-order intermodulation false alarm signal gradually appears. The imaging mechanism, the waveform characteristics, and the level change law of the fifth-order intermodulation false alarm target, are similar to the third-order intermodulation false alarm target, and its position is also random. The maximum third-order intermodulation false alarm signal can reach 18 dBmV, indicating that the radar is sensitive to the out-of-band intermodulation electromagnetic interference