考虑测量带宽影响的电磁干扰频谱FFT计算

EMI Spectrum Analysis Based on FFT With Consideration of Measurement Bandwidth Effect

基于快速傅里叶变换(fast Fourier transform,FFT)计算电磁干扰(electromagnetic interference,EMI)频谱时,为了得到和EMI接收机测试一致的频谱结果,必须考虑测量带宽的影响,即必须将EMI接收机测量带宽内的FFT频率分量在分析频率上进行叠加。提出了考虑测量带宽影响的EMI频谱计算方法,首先对时域信号进行FFT,然后将FFT结果加窗滤波并进行快速傅里叶反变换(inverse fast Fourier transform,IFFT),取IFFT所得波形包络线的最大值作为频谱分析结果。为了提高计算速度,给出了改进的IFFT方法。实验结果表明,所提方法准确有效、计算迅速。

When fast Fourier transform（FFT） is used to analyze the electromagnetic interference（EMI） spectrum,the measurement bandwidth effect must be taken into consideration to obtain results that are consistent with the measurement of the EMI receiver,and thus the frequency components within the EMI receiver measurement bandwidth should be superimposed at the center frequency.A spectrum analysis method based on FFT and considering the measurement bandwidth effect was proposed in this paper.Firstly,the time domain signal with traditional FFT was analyzed.Then,the results were analyzed based on windowed filtering and inverse fast Fourier transform（IFFT）.In order to save the calculation time,an improved IFFT method was introduced.The experimental results indicate that the proposed spectrum analysis method is accurate and fast.