分時多工射頻系統對類比語音電路雜訊干擾分析

Abstract

由於現今的製程科技不斷精進，所有無線產品為了增加其可攜性，不外乎依產品輕、薄以及操作功能強大來發展，進而將所有的功能整合在SOC (system on chip) IC上，衍伸出高速數位訊號與類比訊號彼此太過靠近，造成數位及類比訊號鄰近間相互電磁干擾，進而導致電路操作上的錯誤判斷，其中語音干擾現象更是使用者最不能忍受的明顯干擾。本論文以藍芽(Bluetooth)規範 802.15.1a 為實驗平台，研究分時多工的射頻電路對鄰近語音處理電路之影響，本研究首先探討傳導干擾以及輻射干擾機制；繼而尋求降低射頻電路干擾能力，以及增強音頻電路干擾耐受度的方法，來抑制、減輕操作頻率上的語音雜訊。實驗過程中我們發現射頻功率放大器動作時，因負載效應造成供應電源產生漣波，因而改變音頻輸入端的偏壓，是傳導干擾的主要因素;差動放大器因射頻負載效應亦可導致間歇性的傳導性干擾，造成音頻差動放大器聲音訊號非線性失真進而產生噪音。

As IC process technology continues to improve, wireless products to increase portability, need to be light, thin and powerful. All the integrated circuits operation are implemented in the SOC (system on chip), the high-speed digital signals and analog signals are therefore very close to each other resulting in electromagnetic interference between digital and analog signals, leading to error in the circuit operation. Users can not stand speech interference. This thesis presents the Bluetooth standard 802.15.1a for the experimental platform to study the TDMA of RF circuits nearby voice processing circuits. The first study discusses the conduction interference and radiation interference; in order to reduce RF circuit interference ability and enhance the audio circuit immunity, there are methods to suppress operating frequency noise on the voice. At the final experiment, we found that the RF power amplifier operation presents a variable loading effect to the power supply , the resulting voltage ripple changes the audio input DC bias which led to the audio sound signal nonlinear distortion producing noise appearance.