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为了改善线性失真对荧光LED通信系统性能的影响,首先建立了通信实验系统,采用网络分析仪测量了通信系统的幅频响应,分析了线性失真特性。根据通信系统线性失真的测量结果,设计了一、二、三阶高通滤波器作为线性失真补偿电路,将其与荧光LED通信系统级联,分别测量了级联后系统的幅频响应。结果显示,采用三阶补偿电路后,荧光LED通信系统的线性失真得到了明显改善,系统增益的衰减幅度由补偿前的50dB(0.3~6 MHz)降低为三阶补偿后的20dB(0.3~45 MHz)。为了确保通信系统具有相对平坦的增益特性且要求系统增益的波动小于10dB时,系统的通频带宽度可从补偿前的1.8 MHz提高到三阶补偿后的41 MHz(范围为3~44 MHz),增大了约23倍,且在此频带范围内,系统具有相对较大的增益(约为-30dB)。因此,补偿荧光LED通信系统的线性失真,可以很好扩展通信系统所需的通频带宽度。本文的实验和分析可为进一步优化系统参数及改进通信性能提供参考依据。
In order to improve the effect of linear distortion on the performance of fluorescent LED communication system, a communication experiment system was established firstly. The amplitude-frequency response of communication system was measured by network analyzer, and the linear distortion characteristic was analyzed. According to the measurement result of the linear distortion of the communication system, the first, second and third order high-pass filters are designed as the linear distortion compensation circuit, which is cascaded with the fluorescent LED communication system to measure the amplitude-frequency response of the cascaded system. The results show that the linear distortion of the fluorescent LED communication system is significantly improved with the third-order compensation circuit. The attenuation of system gain is reduced from 50dB (0.3 ~ 6 MHz) before compensation to 20dB (0.3 ~ 45 MHz). To ensure that the communication system has relatively flat gain characteristics and requires fluctuations in system gain of less than 10 dB, the system’s pass bandwidth can be increased from 1.8 MHz before compensation to 41 MHz (range 3 to 44 MHz) after third-order compensation, An increase of about 23 times, and in this band, the system has a relatively large gain (about -30dB). Therefore, compensating for the linear distortion of the fluorescent LED communication system can well extend the required pass band width of the communication system. The experiment and analysis in this paper can provide reference for further optimization of system parameters and improvement of communication performance.