OFDM系统中DAGC的应用研究及FPGA实现

Study and Implement in FPGA of DAGC in OFDM System

介绍IDFT/DFT精度在OFDM系统基带解调中的重要性,分析定点化DFT输入功率对其精度的影响,并在此基础上采用数字自动增益控制技术用于DFT前端,以解决过大输入信号动态范围所造成的DFT输出信噪比恶化的问题。理论分析、Matlab仿真结果以及FPGA实现结果表明,该方法具有可行性、实时性和易实现性,可使DFT输出信噪比达到最佳范围,以满足OFDM系统基带解调的要求;在较大输入功率情况下,采用DAGC技术的防溢出方法和经典DFT防溢出方法相比,前者使得DFT输出信噪比提高24 dB。

The precision of IDFT/DFT is important for baseband demodulation in OFDM system is introduced. Based on analyzing the influence of input power on the precision of fixed DFT, DAGC technique is adopted ahead of DFT to resolve the aggravation of DFT output SNR,which is brought in by the large dynamic range of input signal. The analysis of theory,the result by simulating in Matlab and implementing in FPGA indicate that the proposed method is feasible, real time and simple, which can make the output SNR of DFT in the optimal range on request of base band demodulation in OFDM system. In the case of large input power,the proposed method with DAGC technique achieves a DFT output SNR increase of 24 dB by system simulation,comparing with the classic method which lessens the overflow error of DFT.