Research And Implementation Of Narrowband Multi-channel Satellite Communication Technolagy

Spectrum resources is an extremely valuable natural resources,with the continuous development of wireless communication technology and networking technology,it is bound to cause huge influence and impact on existing spectrum resources.Radio frequency resources are becoming increasingly scarce,so it is urgent to find a new efficient modulation method to significantly improve the spectrum utilization.Therefore,the narrow-band communication technology is increasingly regorded by human.Using narrowband multichannel communication mode is a kind of economical communication strategy.Digital narrow-band communication with high frequency utilization rate,good stability,strong anti-jamming performance,and many other advantages which has better security,flexibility and reliability compared with the traditional analog narrowband communication system.Design and implementation of narrowband multi-channel satellite communication technology is mainly studies in the paper.The subject first put forward a kind of communication combined coding method.BCH encoding,data scrambling,RS encoding and convolution encoding are combined to build a new type of coding constitution.In order to make full use of the spectrum resources,reduce error rate of the stream and improve the secrecy.Delve into shaping filter principle and design it,to eliminate inter-symbol interference as well as to improve spectrum resources utilization efficiency.Before the symbol sequence has been modulated.Secondly,after fully studying the principle of OQPSK modulation,an implementation method without IP core of FPGA is presented.The proposed method improves the portability of OQPSK modulation on the project realization.At the same time,a new solution of OCXO tamed is put forward.Using PID to correct the difference of satellite reference clock and local OCXO clock,so local OCXO clock error of accuracy has been improved 3e-8.The reference frequency of frequency synthesizer unit is provided by OCXO.Up-converter of OQPSK modulated signal is realized in frequency synthesizer unit.Frequency synthesizer unit output frequency range 401.099875 ~ 401.099875 MHz,and can control the RF output of interval is 750 Hz,total 400 channels of the carrier signal,It is make full use of spectrum resource to send signal to the satellite.The design parameters of band pass filter,shaping filter and PID algorithm have beenevaluated by using MATLAB simulation software.The function of coding unit and baseband signal processing unit is verified with MEDELSIM simulation software.To ensure that the hardware description language loaded in FPGA chip is consistent with the expected function.Finally,the instrument is used to test the hardware platform and the test data are obtained and analyzed.The test shows that the design can be divided into a plurality of channels in smaller spectral range,and efficient use of the spectrum resources will be sent data to satellite.To alleviate the pressure of the spectrum provides a method of satellite communications.