近紅外光二極體頻率調變聲音通訊系統，是以近紅外線作為載波光源，把聲音調變在載波中，經由空氣從發射端傳送至接收端，再把收到訊號解調回原音訊而完成整個聲音通訊的過程。本系統採用調頻的方式來作調變，它比振幅調變及相位調變的訊噪比高、失真度低、受環境干擾程度低。 目前許多無線通訊十分熱門，如藍芽之類的大行其道。其優點在於無接線、不怕阻隔。但在稠密的住宅區，若以射頻傳訊，則容易造成互相干擾，且隱密性也大為降低。此時若以紅外光為載波光源，即不用擔心此問題。 本文探討如何運用近紅外光二極體去實現紅外線聲音通訊，並利用前置強調與去強調的方法降低雜訊，使可傳送的範圍及距離增加。 The near Infrared Light emitting diode (IRLED) for FM voice communication system is used near infrared radiation for carrier light source which be modulated by voice signal transmit from transmission port to received port by air, then the received signal demodulate back to the original voice signal. The system takes the FM for modulation method, which has larger signal-noise ratio, lower distortion and surrounding disturbance than AM and PM. The wireless communication is hot, such as blue tooth. Its advantage is wireless and unobstructive, but it easily interfere with each other and isn’t covert in density resident region. If infrared light is took as carrier light source, the problem can be solved. The article surveys how to use IRLED to setup the IR voice communication system and to use pre-emphasis and de-emphasis to lower the noise and improve the width and length of the transmission field.
