| Summary: | 碩士 === 雲林科技大學 === 電機工程系碩士班 === 98 === Because integrated circuits (ICs) in today’s electronic products are deployed much closer than ever before, electromagnetic interference (EMI) problems are more and more serious, making the electromagnetic compatibility (EMC) of ICs an important research topic. According to IEC 61967 standards for integrated circuits electromagnetic compatibility (ICEMC), this thesis aims at constructing near-field measurement fixtures (including electric field probes and magnetic field probes) to measure the field and current distributions around ICs mounted on a printed circuit board (PCB) so as to explore the EMI characteristics on the ICs under consideration.
ICs with embedded active circuits are usually considered the noise sources for the space outside the electronic product. It is conjectured that these noise souce can effectively radiate only if the circuit layout conneting to these ICs are in resonance. To determine the possible radiation effect of a circuit layout, radiation emission measurement was carried in 3-m anechoic chambers and near-field measurement was performed using magnetic field probes. According to the circuit layout of interest, loop antennas of different sizes were designed to facilate the measurement. The equivalent circuits of these loop antennas were found with the help of commercial software simulators by using the measured return losses and input impedances. With the decoupling capacitor mounted on the loop antenna properly changed, the resonant frequency of the loop antenna can be controlled. A 10-MHz square-wave oscillator was used as the signal source of the antenna and the corresponding radiation emission was measured using near-field measurement. It was observe that when the harmonic frequency of the signal source is close to the prrallel resonant frequency of the loop antenna, the radiation is relatively strong. This phenomenon shows that at resonance the circuit layout can produce annoying EMI problem. It also hints that to meet EMC regulations for a commercial electronic product, decoupling capacitors may play a crucial role. A commercial LCD monitor has been employed as a test board in this thesis. Decoupling capacitors in the driving circuit board of the LCD monitor were changed, and radiation emission verification was carried out.
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