Abstract:In order to explore the influence of coaxial cable shielding influencing factors on its shielding effectiveness （SE）， a test set was built based on the shielding attenuation triaxial method to evaluate the SE of coaxial cables and connectors for in-vehicle communication. The effect of the shielding layer， end connector， and segmentation on the SE of coaxial cable was investigated， and the SE test data in the range of 0.1 MHz to 3 GHz was obtained. The analysis results show that for the vehicle communication coaxial cable RG174 series， the double shielding layer is 10~15 dB higher than the SE of the single shielding layer.The cable segmentation and end connector can all reduce their SE. The SE of the cable with the end connector and segmentation is more obvious， and the drop can reach 10 dB.Moreover， the end connector changes the cutoff frequency of the cable. The research results can be used to guide the selection and segment layout design of coaxial cables for in-vehicle communication and solve electromagnetic compatibility problems such as electromagnetic emission and interference of in-vehicle communication equipment in the coaxial cable and their connection parts.

Abstract:Based on GB/T 18655—2018 standard， an experimental system was built for fuel cell vehicles’ DC/DC converter in an anechoic chamber. Conduction emission and radiation emission experiments were carried out. The interference current of each cable port and electric field intensity of the reference point was obtained during the normal operating state of fuel cell vehicles’ DC/DC converter. Then， an electromagnetic simulation model of fuel cell vehicles’ DC/DC converter was established based on the measured geometric parameters of each component in the experimental system. The obtained interference current from the conduction emission experiment was used as the excitation signal of the electromagnetic simulation model. The electric field intensity of the reference point position obtained by simulations was compared with the experimental results. The comparisons show that the overall change trend of simulation results is consistent with the overall change trend of the experimental results. The average error is about 5 dB in the high-frequency band， while the accuracy is relatively poor in the low-frequency band. Overall， the electromagnetic simulation model of the fuel cell vehicles’ DC/DC converter is reliable. Finally， the electromagnetic simulation model was used to analyze the radiation immunity characteristics of fuel cell vehicles’ DC/DC converters. The results show that the normal operating state of DC/DC converters will not be affected in the case of plane wave interference with the electric field strength of 30~100 V/m. Thus， the radiation immunity characteristics of fuel cell vehicles’ DC/DC converters meet the electromagnetic compatibility requirements.

Abstract:According to power system requirements, a kind of threephase multifunctional harmonic energy meter with radio frequency identification (RFID) interface and general packet radio service (GPRS) communication module was developed. The structure and the working principle of the energy meter were described, and its space electromagnetic interference (EMI), conducted coupling interference, and common impedance coupling interference were analyzed. The EMI propagation paths of energy meter were discussed, and the reliability design scheme of energy meter was proposed. The electromagnetic compatibility (EMC) design method of energy meter such as EMC of switch power, PCB routing, communication interface antiinterference design, the antistatic design and software antiinterference design, were analyzed. The EMC test results of the energy meter were given. The experiment and operating results have shown that the threephase multifunctional harmonic energy meter has better EMC.