| Summary: | 碩士 === 國立雲林科技大學 === 電機工程系碩士班 === 97 === In recent years, the rapidly developed fabrication technology has made most electronic products highly densely integrated. Under high-frequency or high-speed conditions, the closer the circuit components are in these products, the higher the chances the electromagnetic interference (EMI) will occur due to cross-talks. For the EMI owing to an entire system, far-field radiation emission (RE) measurements may not provide correct information on which components in the system are the main RE sources. Because of that, near-field measurements should be adopted to locate the main RE sources in the system. In this thesis, a simple procedure is derived for estimating the far-field REs from the measured near-field REs. The estimated results are compared with the measured far-field REs to validate the proposed procedure. The regulation of IEC-61967 has been followed in constructing near-field measurement tools, including E-field probes, H-field probes, and current probes. In order to obtain correct measured results, a microstrip-line calibration method is employed to determine the correction factor of the fabricated H-field probes.
A driving circuit board of an LCD monitor is used as the device under test (DUT). The DUT is measured in the semi-anechoic chamber of NYUST by using the self-made H-field probes. Worst-case REs are estimated and compared with the directly measured far-field REs. Dipole and loop antennas are constructed to validate the estimating procedure. Finally, the circuit layout in the DUT is modeled by dipole and loop antennas of appropriate size. The antenna current feeding currents are measured using the H-field probes and current probes. The far-field REs are then calculated using the antenna model and feeding currents. These calculated far-field REs are then compared with the measured ones. The effects of the number of loops on the far-field REs and the effects of the decoupling capacitors on the EMI are analyzed and discussed.
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