Electromagnetic Interference Effect Research Of OFDM Based On BER

Orthogonal frequency division multiplexing(OFDM)technology has strong anti-narrowband interference and anti-multipath fading capabilities,and is widely used in Radar,Telemetry,WLAN,Military communications equipment,etc.With the increasing number of electromagnetic equipment today,the space electromagnetic environment is becoming more and more complicated,and the interference phenomena such as co-frequency and near-frequency generated by the OFDM system are inevitable.Therefore,studying the effect of different electromagnetic interference on the OFDM system,understanding the law of the interference effect,and analyzing the causes of bit errors are of great significance to further improve and improve the transmission performance of the OFDM system.Existing researches on the effects of OFDM electromagnetic interference,are mainly from the model or just from the software simulation to study the rising factors of bit error rate(BER),systemic and integrity need to be improved.In view of the above problems,this paper selects representative interference patterns in analog and digital electromagnetic interference signals,and comprehensively analyzes the effects of OFDM electromagnetic interference by means of theoretical calculation of bit error rate,software simulation experiments,and hardware-in-the-loop simulation verification.The main contents of this article are as follows:1.The effect of analog electromagnetic interference signals on OFDM is studied.For analog noise interference signals,the bit error rate expressions of barrage noise jamming,spot jamming,partial band jamming,and pulse jamming acting on OFDM are derived based on the noise power spectral density,The simulation shows that when the interference power is constant,the interference bandwidth of partial band jamming is narrow,the energy is concentrated,and the interference effect is good;when the power spectral density is constant,the barrage noise jamming range is larger and the OFDM is more destructive.For analog tone jamming signals,the bit error rate expression of single-tone and multi-tone jamming on OFDM is derived based on the probability density function,and the effect of OFDM on the effect of different tone is theoretically analyzed,the simulation shows that when the tone jamming produces frequency deviation,more frequency points or acts on the pilot subcarrier,it is more destructive to OFDM.For analog non-stationary broadband(Chirp)jamming signals,the impact of different parameters on OFDM is simulated and analyzed,The simulation shows that: only changing the initial frequency,there is no difference in interference effect;only changing the frequency modulation,when the frequency is small,the interference has a greater effect on OFDM;2.The effect of digital electromagnetic interference signals on OFDM is studied.For digital single-carrier modulated interference signals,based on the symbol correlation coefficients,the bit error rate expressions of the frequency shift keying(FSK)type,phase shift keying(PSK)type,and quadrature amplitude modulation(QAM)type interference on the BPSK single carrier system are derived,among them,the FSK type interference effect is poor,however,the simulation shows that because the FSK signal has multiple frequency interferences,it has a greater effectt on the OFDM multi-carrier system using BPSK modulation and avoids the waste of interference power.For digital deceptive interference signals,delay forwarding and asynchronous frequency offset interference are designed,the theoretical analysis of the effect of the system's delay and frequency offset on OFDM,the simulation show that due to the high similarity,deceptive interference has a greater impact on OFDM,and the interference effect is stronger than the single carrier modulated signal;3.Build a hardware experiment platform and design a semi-physical simulation experiment.Choose GNUradio+USRP+Hackrf One software radio combination,design and build OFDM communication link and jammer module,design BER software test platform and six semi-physical simulation experiments,verify the theoretical and simulation analysis,and analyze and discuss the experimental results and the causes of errors,further perfected the research of OFDM electromagnetic interference effect based on bit error rate.