Ofdm Intermediate Frequency Signal Processing System Design

OFDM (Orthogonal frequency division multiplexing) is a multi-carrier modulation technology. The main opinion is to convert the high speed serial data stream to the parallel low-speed data stream. It has lots of advantage, such as high spectrum utilization, strong multipath effects resistance. It can also work well in frequency selective fading or narrowband interference etc. OFDM is suitable for the high speed data transmission in wireless channel. OFDM have widespread application prospect, which is generally considered to be the key technology of the next generation of mobile communication system.This paper studies the basic working principle of the OFDM communication system. At the same time, this paper also analyzes the modulation and demodulation of OFDM, including the key technologies. This paper also contains a comprehensive simulation of the OFDM system.According to the design requirements, an open-planed software defined radio hardware platform is designed in this project. The Xilinx FPGA Spartan3A-DSP is selected as the main digital signal processing chip. High speed ADC, high speed DAC and many peripheral interface equipment are all designed and tested in this hardware platform..This project makes the implementation of a whole OFDM modulation and demodulation based on System Generator. The modulation module contains QPSK mapping, training sequence insertion, IFFT, cyclic prefix insertion. The demodulation contains the OFDM synchronization, delete of the cyclic prefix, FFT, QPSK de-mapping. Based on this achievement, down conversation and up conversation is designed also by System Generator. Finally, by comparing the related data, it is proved that the design is working correctly.