A Study Of Shortwave Communication Coding

Short wave communication is one of the wireless communication which utilize electromagnetic wave whose wavelength is between 100cm and 10m .It can also utilize ground wave or ionosphere to realize communication in range from dozens of kilometers to of hundreds of kilometers or utilize ionosphere to reflect going on to realize communication in rang from thousands of kilometers to remote communication of as many as ten thousand kilometers. As it is one of typical medias of time variance transmitting, ionosphere has auspicious profit decline, many foot-path effect , Doppler effect etc., it will make the code of receiving exhibition wide at time and make envelope distorted, therefore interfering among yards and yard by mistake phenomena will take place during data transmission. This thesis comes to reduce one yard of rates by mistake by making up and modulating demodulation under the great above-mentioned background , thus improve anti-interference performance .This thesis has been described from three following respects:First part: Proceed from project demand background mainly , It has pointed out the actual meaning of developing this system, according to the systematic designing requirement , has put forward the technological key to need solving , has introduced the main research contents of this text briefly , finally it carry on research on the characteristic and development trend of technology of the latest short wave communication technology on modulate or demodulation, it is ready to be proved for the systematic scheme of the next step and designs systematically.Second part : Recommend the short wave communication system to be designed overallly. Three structure form in wireless communication has been carried on theory analyse , point out corresponding applied environment of form. Theory in radio finally carry on research, it is take open to sample to discuss mainly, integer time insert, the integer time collects three kinds of data processing methodsThe third part : Describe various kinds of operation principle , correspondingrealization block-diagram of modulator and demodulator in detail , finally especially expounded the fact that MSK and QPSK modulate demodulation principle , block diagram and code way, and has finished MSK modem and QPSK modem through digital signals chip , such as one-chip computer, DSP ,etc.This text has offered helpful help for making the hardware which modulate demodulation technology up to realize further.