Design And Implementation Of Intermediate Frequency Digital Transceiver Based On OFDM System In FPGA

With the development of the fourth generation mobile communication(4G),OFDM,as the key technology of LTE,becomes a popular technology in the field of communication research.For the advantages of high spectrum efficiency,low cost,good flexibility and abilities of combating inter-symbol interface and multipath fading,OFDM is widely used in modern digital communications.So the performance of OFDM transmission system becomes an important reference index in the digital communication design.The design and implementation of digital transceiver based on OFDM in FPGA device is presented in this paper,which consists of two pieces: the digital baseband transmission system based on OFDM and digital frequency converter realizing the spectrum moving from base band to intermediate frequency.In order to verify the performance of OFDM modulation technology under high-speed signal transmission,the video signal acquired by digital camera is used as input.Firstly,the digital baseband transmission model is designed by using OFDM modulation technology.The implementation of OFDM modulation and demodulation is done by IFFT / FFT,which not only greatly improves the speed of data processing,but also does not need a large number of filter combinations compared with traditional FDM system.Then digital frequency converter is designed by multi-rate signal processing and digital mixing,it realizes the match of samples between baseband and DAC module.Multi-rate signal processing is the key to implementation,and its basic elements are interpolation and decimation.FPGA is used as the hardware plat and the hardware description language Verilog HDL is also adopted to code the module function in this design.The simulation results show that the bit error rate is only 3.8%,which meets the requirements of subject design.Finally,the digital signal processed by the digital processor needs to be converted into an analog signal by DAC and then transmitted to the antenna,therefore,it is necessary to design the corresponding IF antenna to make the whole design more complete,and the size parameters of the 70 MHz microstrip antenna are obtained according to the optimization results.