Research On Wavelet Theory In The Application Of Automotive Electromagnetic Compatibility

The car will not only impact of electromagnetic interference from outside the normal range of electrical and electronic equipment, motor vehicles and will affect an increasing number of its own modernization of the normal electrical and electronic equipment, electronic jamming environment of electronic products will have a negative impact on performance, even Will lead to loss of function. At the system level on the car to predict the electromagnetic compatibility and analysis is necessary. On the motor electromagnetic interference signals in the Analysis and Forecasting has become an important research topic, the last people to signal the approach of the majority is for the theoretical basis for the Fourier Transform, but transient signal Fourier transform reflect a significant lack of At the same time can not meet the time-domain - the frequency domain analysis of requirements, so in this paper we tried to use a new method of analysis - to analyze vehicle wavelet transform the conduction of electromagnetic interference signals, through a number of examples prove that this method is more feasible.The car ignition system into the primary coil voltage side of the gate bipolar transistors insulation (IGBT) as a switch-mode power supply and its work when the transmission interference measurements, and then were used Discrete Fourier Transform (DFT) and based on Morlet wavelet transform the time-frequency analysis of test signals for analysis, because of its good local time-frequency analysis of the ability to identify interference noise electromagnetic shielding measures taken to provide a good basis.Using wavelet packet of electromagnetic interference on car research and highlights the characteristics of the wavelet packet that signal recognition technology, Wavelet packet energy law is interference from the signal characteristics , one of the methods commonly used by experiment found that the adoption of effective non-linear signal wavelet denoising methods, it can significantly improve the recognition rate. Propose a wavelet denoising technology-based non-linear feature extraction algorithm to signal recognition rate from the point of view, choose a suitable non-linear wavelet denoising methods, more efficient extraction of the signal characteristics.through the study found that use of such analysis, could be more accurate to find source of interference signal group, on the basis of this we Use Bayesian analysis to identify, to improve the electromagnetic interference signals a recognition of the progress of the electromagnetic compatibility of car design has played a help.CAN bus signal transmission studied on high-frequency and low frequency coefficient different threshold with mixed threshold denoising treatment. The high-frequency coefficients, based on the likelihood Stein unbiased estimates of the principle of adaptive threshold, because of the interference signal the statistics of unknown circumstances, the coefficient on the threshold of the low-frequency selected to maintain the frequency of a single small loss of energy and the double standards. Finally, the threshold value of the coefficient after Reconstruction signal, the proper transmission code. Experimental results show that the mixed threshold denoising approach to eradicate this from the CAN bus controller on the fault caused by interference, more traditional Noise Cancellation Technology to Improve signal to noise ratio is greatly improved.Finally, Through the analysis demonstrated of the full text , the wavelet transform is a very effective time-frequency analysis tool, it is the vehicle of transmission of electromagnetic interference signals, through research that proved the wavelet analysis in the automotive electromagnetic compatibility testing and analysis of the effectiveness.Reflects the value of this study.