Time-domain EMI measurements in the presence of ambient noise

This paper presents adaptive cancelation techniques to suppress ambient noise in electromagnetic interference measurements on open area test sites. The measurements are carried out in time-domain to reduce the total measurement time. To achieve optimum cancelation, time-domain as well as frequency domain adaptive filter algorithms have been investigated and compared in respect of their suppression performance. An advanced digital signal processing technique for fast measurements of electromagnetic interference from electronic devices is presented. Fast measurements of electromagnetic interference of electronic devices and systems are carried out on a test site polluted by electromagnetic ambient noise. Frequency domain adaptive filtering using the overlap-save method is applied. Measurements of a personal computer as device under test are carried out on an urban test site showing the successful cancelation of ambient noise in a frequency range from 30 MHz to 1 GHz.