|
Modulation and demodulation is an important key technology in optical communication. The design of modulation and demodulation will directly affect the transmission quality of the whole system. Therefore, the design of modulation and demodulation system is of great significance to the application of optical communication. In this paper, the PPM modulation and demodulation is designed as an independent module in FPGA, which is convenient for people to use. Through the oscilloscope, FPGA development board, PC hardware system and Quartus II, serial assistant, mdelsim software system to verify the design of the modulation and demodulation module function. PC serial port is used to send unmodulated digital signal to FPGA development board. FPGA modulates the data received by serial port. The modulated signal is divided into two channels. One channel is sent to PPM demodulation module. The demodulated signal and the other modulated signal are sent to PC through serial port. The oscilloscope is used to capture the sending and receiving pin signals. By comparing the waveform and serial port of the oscilloscope, two channels of waveform are compared Hand data to verify the design of the module. The main working process of PPM modulation module is to collect the original digital signal by sampling clock, and then to modulate it into PPM signal after buffering, encoding, storing and shifting. Ppm demodulation module collects PPM signal by sampling clock, caches, decodes, registers and shifts output, and finally demodulates the original signal. Through Modelsim simulation and oscilloscope hardware platform experiment, it shows that the PPM modulation and demodulation module designed in this paper has strong antiinterference ability, low bit error rate, convenient and flexible, and has good engineering application value. It realizes higher communication rate in optical communication system and improves the reliability of transmission system, which is very important for optical communication.
|
