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LED作为可见光通信(VLC)的发射光源时为保证足够大的光信号覆盖范围和信号强度,应采用大电流脉冲调制。本文研究了大功率LED的光-电脉冲响应比小功率器件较慢、从而造成光调制带宽降低的原因,以及LED注入电子和空穴的缓慢复合与驱动电路晶体管在大电流工作时的存储效应;由此设计了FPGA控制下的光脉冲整形方案,信号脉冲经由FPGA再生同时产生另外两路相位关联的短脉冲,同步控制驱动电路分别在信号脉冲上升沿施加一个瞬时高压加速载流子注入,在脉冲下降沿使LED两端短路将剩余载流子泄放,使光脉冲边沿加速进行整形。对接收信号的眼图和误码率(BER)的测试结果表明,在接近安培量级的峰-峰值调制电流下,通过这种同步控制方法使光信号质量得到有效改善,传输速率得到明显提高。
LED as a visible light communication (VLC) when the light source to ensure adequate coverage of the optical signal and signal strength, the pulse should be used for large current modulation. This paper studies the reason why the optical-electrical impulse response of high-power LEDs is slower than that of low-power devices, resulting in the decrease of optical modulation bandwidth and the storage effect of the slow recombination of LED injection electrons and holes and the driving transistor in high-current operation The pulse shaping scheme under the control of FPGA is designed. The signal pulse is regenerated via FPGA simultaneously to generate two more short pulses of phase correlation. The synchronous control driving circuit respectively imposes an instantaneous high-voltage acceleration carrier injection on the rising edge of the signal pulse, In the pulse down the LED short-circuit the two ends of the remaining carrier discharge, the optical pulse edge acceleration to shape. The eye diagram and bit error rate (BER) test results of the received signal show that the optical signal quality is effectively improved and the transmission rate is significantly improved by this synchronous control at a peak-to-peak modulation current close to ampere .