简易数字信号传输性能分析仪的设计

Design of simple digital signal transmission performance analyzer

为了更好地分析数字信号在传输过程所受码间干扰和噪音等因素的影响,文中设计了一个以FPGA为核心的简易数字信号传输性能分析仪,完成了数字信号发生器、伪随机信号发生器(模拟噪音源)、低通滤波器、加法器、数字信号分析电路的设计.该系统利用FPGA产生数字信号序列(M序列和曼彻施特编码序列)和模拟噪声序列(伪随机信号),经过由低通滤波器构成的模拟信道进行传输,再由FPGA对数字信号分析提取出同步信号,最后在示波器上以眼图的形式来分析信号的传输性能.对截止频率与通带增益、数据率误差和眼图进行了实测,结果表明误差值均在允许范围内,系统工作稳定,眼图清晰,达到了设计要求的各项指标.

This paper designs a digital signal transmission performance analyzer, using FPGA as its core, to further analyze the effect of inter-symbol interference and noise on digital signal during the transmission process. A digital signal generator, a pseudo random signal generator （analog noise source）, a low-pass filter, a adder, and a digital signal analysis circuit were completed. The system generates a digital signal sequence （the M sequence Mancheshite coding sequence） and a pseudo noise sequence （pseudo random signal） by using FPGA. These sequences were ti^ansmitted by a low pass filter. Then we analyzed digital signal, extracted synchronization signal by FPGA. Finally we analyzed the performance of signal transmission through the eye diagram on the oscilloscope. We measured the cutoff frequency and passband gain, data rate error, and the eye diagram. The test results show that the error values are within the allowable range, stable system, and clear eye diagram. It meets the design requirements.