External Electromagnetic Interference Of Wired Communications Equipment

Intentional Electromagnetic Interference or IEMI to wired communicationequipments was used largely not only in modern war, but also by terrorists,criminals whose purposes were to make the communication equipments not beable to operate normally. And so, it caught many countries'high attention tostudy the interference of external electromagnetic fields to wiredcommunication equipments and understand the anti-jamming ability of wiredcommunication equipments to external electromagnetic fields radiation.In this thesis, it was regarded as research object that based on theinterference of plane wave which sine amplitude modulation signal generatedto wired telephone, as research method that based upon theoretic model andcomputation, software simulation, noise voltage level test and sound intensitytest; it was analyzed the coupling approaches of electromagnetic fields towired telephone, the reason of generating noise and the frequency response oftelephone by combining the results of theory computation, softwaresimulation and test.This paper also built up a lot of equivalent receive models, includingtransmission line model, helical antenna model, electric dipole model,magnetic dipole model, lumped element RLC equivalent model. Thecoupling quantity of incident electromagnetic fields to each model wasobtained by detailed analysis and computation. It was ensured that the mainreason of generating noise was the demodulation function of triode amplifierin receive circuits by identifying the non-linear components. Softwaresimulation obtained the frequency response of telephone, the susceptibilitycurve of non-linear components and the most susceptibility circuits oftelephone. The main demodulation frequency rang was below 500 MHz, andtelephone can hardly demodulate upon 500 MHz. Study of the interference ofexternal electromagnetic fields to wired communication equipments will havevery important practical value for increasing the anti-jamming ability of wiredtelephone to external electromagnetic fields radiation during design.