Analysis And Design Of Radiated Emission Measurement System In Complex Electromagnetic Environment

An innovative measurement system of radiated emission from devices under test at complex electromagnetic environment is presented. Processing the received signal by using the signal processing techniques can suppress ambient noise. By the signal processing, the measurements of Equipment under Test (EUT) can be performed at a test site polluted with electromagnetic ambient noise. The coherence of ambient noise is computed by using the singal analysis in time domain and frequency domain. With the characteristic of ambient noise, it can be suppressed by the threshold function, 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 cancellation of ambient noise can be obtained in the frequency range of 9kHz to 2.7GHz.Our contributions include:1. Aim at the problems in measuring of radiated emission from devices under test at complex electromagnetic environment, this dissertation introduces some methods existing, like time-sharing measurement and time synchronous measurement presented by Marino, Jr, then, the shortages of these methods is analysed. After that, design of our measurement system and hardware components and the software has been introduced.2. Adaptive filtering method and time frequency statistical algorithm have been used in suppressing ambient noise, and the spectral correlation has been used in EMI source location.3. An improved virtual chamber test system combined the time sharing measurement and synchronized measurement for on-site EMI measurement. This system can remove the time asymmetrical and space asymmetrical, so it can be more practicality.