荧光LED通信系统线性失真测量及其补偿

Linear distortion measurement and compensation for an LED communication system

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 eliminate the effect of linear distortion on the characteristics of fluorescent LED based communication system, an experimental system based on fluorescent LED is established, a network analyzer is then used to analyze amplitude-frequency response curve of the system, and the linear distor- tion performance is analyzed. Based on the attenuation characteristics of the amplitude-frequency re- sponse,the first-, second- and third-order high-pass filters are designed as linear distortion compensation circuits, and the amplitude-frequency response curve of the system with distortion compensation is fur- ther measured with the network analyzer. Experimental results indicate that by using the third-order post-equalization circuit, the linear distortion of the system is obviously improved, and the decrease of the gain is improved from 50 dB within the range of 0.3--6 MHz before compensation to 20 dB within the range of 0.3--45 MHz with 3rd order compensation. To ensure relatively flat gain characteristics of the communication system and obtain a small gain variation of less than 10 dB, the bandwidth is enlarged from 1.8 MHz before compensation to 41 MHz （the range is 3--44 MHz） with 3rd order compensa- tion,indicating an increase factor of 23 ,and within this frequency range,a larger gain of --30 dB is also achieved. Therefore,by compensating the linear distortion of the communication system, its bandwidth can be effectively enlarged. The proposed experimental and analytical results in this paper can provide data basis for svstem 13arameter optimization and further improvement in communication performance.