Research On Radio Technology Based On OFDM

OFDM is a kind of orthogonal multicarrier modulation technology,which has the advantages of high bandwidth efficiency and anti-multipath delay.After the scheme of realizing OFDM system by IFFT is proposed,the digital realization of this modulation technology becomes simple,and then it has been widely used in the field of communication.Radio station using OFDM modulation and demodulation technology can be better adapt to the complex and changeable environment in land warfare,and meet the need of more and more data transmission.The design of the OFDM radio station is helpful to perfect our country's modern information war system,to ensure the transmission security of text instruction,image information and language information in the course of war,and to complete the real-time communication.In this paper,the overall design scheme of the OFDM radio station is given,the key technologies in OFDM system are analyzed in detail,and the hardware structure of the radio station development board is briefly introduced.As the core of the whole development board,FPGA chip needs to complete the baseband signal processing and the configuration of related chips,including the timing design of DAC chip(AD9763)and ADC chip(AD9218).Using the state machine in the hardware description language to configurate the local oscillator chip(ADF4351)and the network interface chip(W5300),and then the necessary carrier signal is generated and the Ethernet data communication between the PC and the development board is completed.After that,the design of OFDM system in IEEE 802.11a standard is deeply studied.With reference to its frame structure,transmitting flow and receiving synchronization algorithm,the data frame structure of the radio station has been designed.The transmitter module of the radio station is coded in the integrated development environment(ISE),and the synchronization algorithm related to the receiver module is also coded.Finally,the transmitter module of the radio station is tested on the board.The BPSK signal produced by OFDM modulation is demodulated by signal analyzer,and the EVM is less than 9%.At the same time,two development boards are used to complete the joint debugging of transmitter and receiver modules,which can capture the arrival of frame data accurately.The final test results show that the transmitter module of the OFDM radio station can provide an effective bandwidth of about 4 MHz,also,can meet the requirements of 2 Mbps code rate.The timing synchronization algorithm of the receiver module is correct and feasible,which can capture the data frame and locate the symbol accurately.