Design Of DRM Communication System

HF high-speed bridge modem is a solution for customer's request as a result of the bandwidth of current offshore shortwave communication is small and the transmission rate is slow.The design and implementation of the system is carried out in this dissertation.The system is based on Digital Radio Mondiale(DRM)broadcasting system of communication system with using sophisticated technology of Orthogonal Frequence Division Multiplexing(OFDM)modulation and demodulation and punctured convolutional codes.Compared with short-wave communications technology currently used in the ocean,it has the ability of high transmission rate,anti-fading,anti-multipath.This dissertation describes the development,the basic structure,transmission mode and programs of DRM broadcasting systems.Three technical solutions with an encryption and decryption circuit solution according a hardware perspective are proposed in this dissertation.It analyzes the advantages and disadvantages of the three hardware solutions.This dissertation also makes algorithm analysis of each function module according a software perspective and describes software architecture of embedded system and programmable logic unit.In the last part,it describes the functions of structural units in detail and focuses on the part of the algorithm.This dissertation implements signal processing module in the HF high-speed bridge modem which includs baseband and digital IF signal processing for the signal sending and receiving.The signal processing module is based on DRM system,it achieves the source encoding,main service channel reuse,energy dispersal(short PN sequence scrambling),convolutional encoding,channel interleaving,modulation,upconversion and other functions in the transmission channel.It also achieves the down-conversion,demodulation,deinterleaving,channel decoding,descrambling,demultiplexing,source decoding and other reverse function in the receiving channel.