VLC系统偏置电流对LED调制带宽的影响分析

偏置电流对LED内部温度、结电阻和载流子浓度产生的变化导致LED频率响应发生改变。分析了偏置电流对LED频率响应的影响机理以及对调制带宽的影响规律，并通过测试平台进行了测试验证。结果表明:红、绿、蓝LED工作在额定功率以下时，偏置电流与调制带宽基本处于线性正比关系，在接近和超过额定功率时，调制带宽变化缓慢并最终趋于稳定。偏置电流对荧光粉LED的调制带宽几乎没有影响。此研究对可见光通信系统偏置电流的选取及均衡电路的设计提供参考。

Analysis of influence of VLC system bias current on LED modulation bandwidth

Bias current exerts influence on the LED performance parameters including the internal temperature, junction resistance, and the carrier concentration, which has an effect on frequency response. In this paper, the influence mechanism of bias current on frequency response was analyzed, and the influence trend of DC bias on modulation bandwidth was researched and tested. The results demonstrate that the bias current is basically linearly proportional to the modulation bandwidth while LED's (red, green or blue) working power is less than the rated power. When the working power is close to or exceeds the rated power, the modulation bandwidth will change slowly and eventually stabilizes. With respect to phosphor LED, the bias current has almost no effect on it. This study may provide reference for the selection of bias current and the design of equalization circuit in visible light communication system.