基于小波分析的电磁干扰测量技术研究

该文提出了一种新颖的可在开阔场快速测试受试设备的电磁干扰的数字信号处理技术。利用小波变换对测试信号分频滤波处理，可以在被环境噪声污染的地方进行受试设备的电磁辐射干扰测试。基于小波分析的阈值函数滤波方法得到应用。利用小波分析时频都可局部化的特点计算出环境噪声的相关性，提取出噪声的时频特性，并由给出的阈值函数对噪声滤除或者衰减，得到受试设备的实际电磁辐射信号。测试方法使得受试设备不必进入暗室即可进行电磁辐射干扰测量，既节省了测试费用又方便了受试设备的电磁干扰测试。系统运行结果证明此方法在30 Hz~1000 MHz的频段内成功衰减并滤除了环境噪声。

The Study of Electromagnetic Interference Measurement Technique Based on Wavelet Analysis

A innovative digital signal processing technique for fast measurements of ElectroMagnetic Interference(EMI) from devices under test in the time-domain at open area test sites is presented. Suppressing ambient noise by using the wavelet analysis, the EMI measurements of an Equipment Under Test(EUT) can be performed at a test site polluted with electromagnetic ambient noise. Frequency-domain threshold funtion filtering using the wavelet analysis method is applied. The coherence of ambient noise is computed by using the wavelet analysis in time domain and frequency domain. With the characteristic of ambient noise, it can be suppressed by the threshold function in the wavelet domain, and the pure electromagnetic radiation can be obtained readily. The EMI measurement can be performed without the anechoic chamber. It is seen that it is convenient to perform the EMI measurements while the total cost can be reduced greatly. Measurement results show that the successful cancelation of ambient noise can be obtained in the frequency range of 30 Hz to 1000 MHz.