Design And Implementation Of Transmitter Based On Software Radio Platform

This thesis focuses on the wireless transmission of high-definition video between UAV and ground.On the basis of system simulation,transmitter prototype adopting the DVB-T standard was developed making use of the software radio platform.The system test result shows that the design scheme of the transmitter is feasible,and the performance index meets the design requirements.In view of the complexity of UAV transmission channel and the requirements of high transmission quality,the system designed in this thesis adopts DVB-T(Digital Video Broadcasting-Terrestrial)standard.The modulation scheme of DVB-T is Coded Orthogonal Frequency Division Multiplexing(COFDM),which has high spectral efficiency and special advantages in anti frequency selective fading,flat fading and Doppler shifting.The constructed transmitter consists of AD9361 module and AX7350 development kit,which as the RF front end and the baseband processing unit,respectively.It has the characteristics of good flexibility,strong function scalability,high reliability and can find wide application range in the future.This thesis focuses on the realization of the transmitter system taking advantage of software radio technology.The work in this thesis includes both the baseband part and the RF part development.In the baseband part,some function modules were designed,such as energy dispersal,outer coding,outer interleaving,inner coding,inner interleaving,constellations mapping,framing,IFFT modulation and guard interval insertion modules in DVB-T standard,and the algorithm and timing simulation were completed.Further more,the board-level verification was finished on the FPGA platform.The main work of the RF part is: optimizing the design of the communication interface between the baseband and the RF part,realizing the real-time data transmission between the AD9361 software radio module and the AX7350 development board,and generating modulated signal of orthogonal signal and QPSK.This design reduces the consumption of logic resources in FPGA and enhances the versatility and portability of the modulation platform.The thesis uses Verilog language to realize the function of each module,and completes the simulation and verification of each module in Matlab and Vivado development environment.The debugging results of the system show that the transmitter developed in this thesis conforms to the standard,and the EVM(Error Vector Magnitude)is small,which can transmit data stably and reliably,and can provide technical support for the wireless video transmission of UAV.