Design Of Highly Integrated DMB Transmitter For Emergency Communications

Broadcasting is the most effective means of disseminating information in major disasters,and also is the only means in many cases.Digital Multimedia Broadcast(DMB)has higher spectral efficiency and richer business content than traditional analog broadcasting,and can play a greater role in early-warning release and emergency communication.However,the traditional transmitter is bulky,which is not conducive to flexible deployment in emergency situations.This thesis adopts System on Chip(SoC)architecture to design a highly integrated DMB transmitter for emergency communication.Meanwhile,this thesis uses the transmission and reception cooperative control mechanism to realize bidirectional communication between two transmitters,which provides a new technical means for major disaster emergency communication.This thesis firstly studies the structure of DMB transmission system,and then designs a highly integrated DMB transmitter based on SoC FPGA single-chip architecture by using software and hardware collaborative design method.The hardware of this transmitter includes baseband circuit based on SoC framework and up-conversion circuit.In the deisgn of baseband circuit,the DMB baseband processing circuit such as Orthogonal Frequency Division Multiplexing(OFDM)modulation circuit and synchronous network control circuit is encapsulated into DMB baseband processing IP(Intellectual Property)core with Avalon bus through the Qsys system integration tool,and then integrate this IP,peripherals and hard processor together to form a highly integrated SoC system.The upconverter circuit is designed based on the orthogonal digital up-converter AD9957,which is used to realize the conversion of digital Intermediate Frequency(IF)signal to Radio Frequency(RF)signal.In the design of SoC software,the C language is used to complete the main control program of transmitter.The basic launch function of DMB transmitter is realized through the unified configuration and management of SoC system peripherals and AD9957 by the hard-core processor.Next,add a receiving module to the transmitting system,which enable the DMB transmitting system to have the receiving capability.And then design a mechanism of data exchange based on the dedicated channel of bidirectional communication and a software for controlling data sending and receiving to realize bidirectional communication between two transmitters.In addition,make tests to verify the feasibility of the Single Frequency Network(SFN)scheme based on the transmitter designed in this thesis.Finally,test all designs of this thesis.The test results show that:(1)The overall size of the DMB transmitter hardware circuit is 115 mm × 108 mm × 20 mm,which meets the requirements of high integration.(2)The RF signal power output by the DMB transmitter is-20.4dBm,and the adjacent channel rejection ratio is in the range of-54.8dB to-57.4dB.The DMB receiver can receive program information,the basic emission function of DMB transmitter is normal.(3)Two transmitters in bidirectional communication test can realize bidirectional communication of text,file,voice and video data,which enhances the business ability of DMB in emergency communication situations.(4)In the test of SFN scheme,the time-delay difference of RF signals output by two DMB transmitters is kept within 8?s,and the superposed signal is normal,which proves that two RF output signals in the SFN scheme can be synchronized.