Research On Time Frequency Modulation Receiving Processing Terminal Based On PC

Short-wave communication is one of the earliest and widely used wireless communication mode.Due to the impact of satellite communication,optical fiber communication rapid development,the short-wave communication is on its low ebb.In the 1980s,because short-wave communication is independent and has the characteristics of fast recovery,flexibility,so it gets attention again.With the development of wireless communication technology and the application,the traditional analog receiver is difficult to meet the needs of modern short-wave communication,so the software radio technology is introduced into the shortwave communication.This thesis based on PC software to achieves time-frequency modulation baseband signal's receiving and processing,which takes advantage of software radio technology.To improve the quality of short-wave data communication,baseband signal use 4TFSK time-frequency modulation technology,and error control techniques use Golay Code?interleaved technique and time diversity technique.The receiving terminal implements demodulation and decoding of time-frequency modulation base-band signal.This thesis mainly includes the following aspects:it first elaborates the research background and research situation of the short-wave communication and software radio technology,and illustrates technology can eliminate the fading and multipath in short-wave channel.Then according to the time-frequency modulation optimal receiving principle to design the base-band modulation signal demodulation module,which mainly includes the sampling rate conversion module,matched filtering module(related calculation module),low pass filter module and likelihood decision module,and each module data analysis diagram is given.The time slot synchronization module of likelihood decision module which take advantage of quadrature encoder feature of madulation signals to tick out bit synchronization signal has a synchronous reference way.Finally,to design the decoding module,and it mainly includes the mixed solution module,frame synchronization module,time diversity signal acquisition module,and Chase soft error correction module and format output module.Frame synchronization module aims at the sending signal data format,and to realize frame synchronization process according to certain rules,which enhances the ability of the permissible error of frame synchronization.In addition,to deal with the deep decline phenomenon,it adopts the technology of time diversity,which has overcome the signal attenuation effectively and improve the quality of shortwave communication.