数字基带信号直接传输系统的研究与设计

Research and implementation of digital baseband signal transmission

数字基带信号的直接传输会随着传输距离的增加而使得信号幅度逐渐衰减.为了提高传输质量,提出了一种基于高速模数转换器和最小二乘法自适应均衡的软阈值数字基带信号直接传输方法,使用模数转换器的接收机替代传统的均衡器芯片,对波形进行多级量化,并在自适应均衡后输出信号.首先使用高速模数转换器接收非屏蔽双绞线传输的基带差分信号波形,然后通过软阈值自适应均衡算法进行信号整形,最后将每个二进制数据位软信息组成的多级数据序列作为Turbo译码器的输入信号.电路实验中,在发送端通过1个199 m和1个201 m的非屏蔽均匀铜质双绞线输出12.5 MHz伪随机序列,实现了数字基带信号的时钟提取以及软阀值的均衡输出.该方法延长了数字基带信号的传输距离,同时也保证了数字基带信号的传输质量.

The signal amplitude of the digital baseband signal direct transmission will gradually attenuate as the transmission distance increases. In order to improve the transmission quality, the receiver based on the analog-to-digital converter was presented, instead of the traditional equalizer chip. At the same time, a multi-level quantizer of input waveform and an adap- tive equalizer are described in detail. First, a high-speed analog-to-digital converter is used to receive unshielded twisted-pair transmission of the baseband differential signal waveform. Then, the soft threshold adaptive equalization algorithm is used for signal shaping. Finally, the muhi-level data sequence consisting of each binary data bit soft information is used as the input signal of the TURBO decoder. As a result, a 12.5 MHz pseudo-random sequence transmitted through a 199 m and a 201 m unshielded uniform copper twisted wire pairs. The clock extraction of the digital baseband signal and the balanced output of the soft threshold are realized. This method makes the transmission distance of digital baseband signal longer, while ensuring the transmission quality of the digital baseband signal.