Time-domain low-frequency non-periodic transient EMI measurement system

In this study, a time-domain low-frequency non-periodic transient electromagnetic interference (EMI) measurement system is presented. By the use of an antenna, an anti-aliasing filter, and a digital oscilloscope, the radiated emissions measurement specified by electromagnetic compatibility standard MIL-STD-461 is achieved. In the first stage, the antenna receives the radiated emissions of the device under test and the time domain output voltage is acquired in the oscilloscope. Then, to fulfil the spectrum measurement as accurate as an EMI receiver, a spectrum calculating methodology is carried out. Optimised inverse fast Fourier transform procedure for spectrum estimation in the proposed methodology is implemented to reduce the calculation efforts. The proposed EMI measurement technique required only a single time-domain acquisition and no repeatedly continuous scanning was imposed on the frequency measurement of the EMI test receivers. Due to this benefit, scan times are decreased by several orders of magnitude in comparison with a traditional EMI receiver.