Research On Electromagnetic Interference Effect Of Typical Software Radio RF Front End

As the radio frequency noise in the communication environment increases year by year,the space electromagnetic energy is dense,and the electromagnetic reliability of the communication system is prominent.Software Defined Radio(SDR)has been widely used in the field of modern communication because of its outstanding advantages of openness,flexibility and expansion.Because the RF front-end of SDR covers a wide range of frequency bands,it is vulnerable to external electromagnetic interference,resulting in serious interruption or paralysis of the communication system.Therefore,in-depth research on the electromagnetic interference effect of SDR RF front end has important practical significance to improve the anti-interference ability of wireless communication transmission and robustness in complex electromagnetic environment.Aiming at the electromagnetic reliability of typical SDR communication system,this paper carries out the mechanism analysis,experimental verification,modeling and simulation of electromagnetic interference effect in SDR RF front end.Firstly,the electrical functional structure and electromagnetic damage characteristics of SDR RF front end are analyzed,and the mechanism of electromagnetic interference coupling effect of SDR RF front end is revealed.Then the experimental system of SDR radio frequency interference and continuous wave injection interference are designed and built,and the electromagnetic interference error characteristics and bit error rate prediction models of typical SDR communication systems are obtained.Finally,the electromagnetic sensitivity simulation experiment of RF front-end low noise amplifier(LNA)is completed,and the equivalent model of electromagnetic interference damage behavior is given.The main research contents and innovations of this paper are as follows:1.According to the electromagnetic characteristics and interference characteristics of software radio system,the electrical function structure and electromagnetic interference coupling mechanism of SDR RF front-end are analyzed.By studying the working principle and electrical structure characteristics of SDR,the functional module composition and electromagnetic information technology index of RF front end are analyzed,and the mechanism of electromagnetic interference effect is expounded from the aspects of interference coupling path,interference characteristics and damage characteristics.2.The experimental system of RF interference effect of software radio is designed,and the information error characteristics in different interference scenarios are given quantitatively.The SDR communication interference experimental environment is studied and built,and the QPSK digital band transmission system is developed and designed by using MATLAB/Simulink software.Through the experimental observe and recording of the disturbance characteristics of communication signal eye diagram and constellation chart,the bit error rate of the communication system under different interference frequency and power is analyzed.The results show that the communication system fails when the bit error rate is 0.25,and the variation trend of adjacent frequency interference with interference power is consistent with that of co-frequency interference,but the minimum interference power with bit error is 0～20d B higher than that of the same frequency.In the case of the same bit error rate,the power of out-of-band strong electromagnetic interference signal is proportional to the signal frequency offset.3.The experiment of continuous wave(CW)injection interference in the front end of software radio is designed,and the electromagnetic interference sensitive bandwidth and sensitive threshold curve of SDR are given.The nonlinear characteristics of RF front end under interference coupling are analyzed,the sensitive bandwidth is tested by frequency sweep,the CW injection interference experiment at sensitive frequency points is designed and completed,the sensitive threshold of RF front-end is tested,and the sensitive threshold curve is given.The results show that the sensitive bandwidth of the SDR RF front-end is about 10 MHz,which is wider than that of the receiver,and the critical interference field strength increases rapidly when the frequency offset is in the 2MHz range,which is consistent with the performance of the RF front end filter.4.Based on the experimental data of RF interference and injection interference in software radio system,an equivalent loss model of RF front-end sensitive devices is proposed.The degraded damage phenomenon of LNA under the action of electromagnetic pulse is analyzed.Based on the failure mechanism of PHEMT,the equivalent damage models of gate-source and gate-drain are established,and the protection scheme of RF front end is given.