基于全数字锁相环的直流载波系统设计

Design of DC carrier system based on all digital phase locked loop

为了实现信号线和电力线的复用,提出了一种直流载波系统的设计方案。信号由频移键控的方式进行调制,调制信号控制MOS管输出脉冲信号,通过变压器耦合到传输介质M30总线上;接收端的脉冲信号通过比较回路转为数字信号,最终经全数字锁相环同步后进行解调。设计了基于Xilinx公司的FPGA芯片和ISE环境的软硬件系统,其中串口模块,FSK调制解调模块和锁相环都是Verilog编程实现的,并在Modelsim中进行了仿真,证明系统逻辑功能可靠。利用串口发送数据,实验证明了该系统能够正确收发数据。

This paper presents a method of license plate character recognition based on the combination of Zernike moment and wavelet transformation features.In order to realize the multiplexing of signal line and power line,a design scheme of DC carrier system is proposed.The signal from the frequency shift keying modulation method,modulation signal to control the output pulse signal of MOS tube,through the transformer coupled to the transmission medium of M30 bus;the pulse signal receiver through the comparison circuit to digital signals,the digital phase-locked loop synchronous demodulation.A software and hardware system based on Xilinx＇s FPGA chip and ISE environment is designed.The serial port module,FSK modulation and demodulation module and PLL are all programmed by Verilog,and are simulated in Modelsim,which proves that the system logic function is reliable.Using the serial port to send data,the experiment proves that the system can receive and receive data correctly.