- 學位論文
手持裝置TDMA雜訊之分析與抑制
Analysis and Suppression of TDMA Noise for Handheld Device
摘要
本研究透過佈線分析、金屬屏蔽與元件濾波方式來改善手持裝置中因分時多工存取(Time Division Multiple Access ; TDMA)產生之雜訊(Noise)干擾。藉由印刷電路板(Printed Circuit Board ; PCB)以及軟性電路板(Flex Printed Circuit ; FPC)上的走線分析，以及實際傳輸線串擾的模擬與量測，確認干擾源來自天線發射時耦合至一FPC軟板音頻路徑上。 本文提供三種方式在行動電話傳輸語音訊號時的耳機聽筒遭受GSM850, GSM900之TDMA雜訊干擾，透過對雜訊源做走線調整、金屬屏蔽、電容濾波等方式做分析改善，藉此了解抑制方式的選用。由頻譜分析儀量測，調整走線前量測雜訊干擾功率為-86.91 dBm，改善後為-91.46 dBm，可改善4.55 dB;使用金屬屏蔽方式量測雜訊干擾能量為-86.91 dBm，改善後為-112.3 dBm，可改善25.39 dB;使用電容濾波量測雜訊干擾功率為-86.91 dBm，改善後為-105.99 dBm，可改善19.08 dB。 針對音頻改善測試，使用頻譜分析儀與示波器去量測音頻訊號改善程度，在一FPC軟板上以金屬屏蔽效果最好，但是在成本與時間限制考量下，使用電容濾波改善輻射干擾是較可行的方案。
並列摘要
This work focuses on the reduction of TDMA noise for handheld devices. There are several approaches to achieve this objective, including PCB layout modification, metal shielding, and capacitor filtering. Through layout routing analysis in PCB and FPC board as well as the simulation and measurement of cross talk between transmission lines, the noise source can be confirmed by coupling the audio path when antenna transmits signals. After that the three reduction methods will be applied. Depend on measured results in spectrum analyzer, the measured noise spur is -86.91 dBm for failed device. (1) After modifying layout routing, the measured noise spur for 217 Hz is -96.41 dBm which is improved by 4.55 dB. (2) By using metal shielding on audio path, the measured noise spur is -112.3 dBm which is improved by 25.39 dB. (3) By using de-coupling capacitor, the measured noise spur is -105.99 dBm which is improved by 19.08 dB. For audio test, uses spectrum analyzer and scope to measure the improved level. Shielding the related components on FPC has the best effective. However, if takes the cost and time limitation into account, using components to reduce interference is a more feasible solution.