全相位FFT的OFDM系统ΣΔ量化噪声整形

摘要

To solve the problem of quantization noise in OFDM systems,a study of sigma-delta quantization noise shaping based on the all phase FFT is presented.This paper first gives single zero and multiple zeros sigma-delta modulators used for the theoretical analysis of quantization noise shaping for the OFDM system,and points out that the non-cyclic quantization noise structure results in inter-carrier interference (ICI) and inter-symbol interference (ISI) of quantization noise at the frequency points of OFDM sub-carriers;then it gives the scheme and performance analysis based on the all phase FFT to further reduce the quantization noise at the frequency points.Simulations show that the multi-zero sigma delta modulator performs better in noise shaping compared to the conventional single-zero modulator in OFDM systems,and can further reduce the quantization noise,and that under the conditions of 2bit quantization and 5dB SNR,the bit error rate of the system deceases by 1 order of magnitude.%针对正交频分复用系统的量化噪声问题,提出基于全相位快速傅里叶变换的ΣΔ量化噪声整形方法.首先给出单零点与多零点ΣΔ调制器用于正交频分复用系统量化噪声整形的理论分析,指出非循环的量化噪声结构使各子载波频点处存在累积量化噪声;进而给出基于全相位快速傅里叶变换进一步降低频点处量化噪声的方法与性能分析.仿真表明,在正交频分复用系统中,多零点ΣΔ调制器具有比单零点ΣΔ调制器更好的量化噪声整形性能,引入全相位快速傅里叶变换使系统量化噪声进一步降低,在2bit量化、信噪比为5dB时,基于多零点ΣΔ调制的正交频分复用系统误比特率降低了一个数量级.