DVB-T/H调制器中多模式OFDM的FPGA设计与实现

Design and Implementation of Multi-mode OFDM in the DVB-T/H Modulator Based on FPGA

阐述2K、4K和8K三种模式兼容的正交频分复用(OFDM)的实现方法,给出综合与仿真验证结果。核心模块快速傅立叶逆变换(IFFT)采用基于16位定点运算的基-2时间抽取算法和流水线结构。为防止定点溢出,提高精度,采取位扩展、输出数据统计定标等措施,在三种工作模式下,IFFT的输出信噪比均达到74dB。在OFDM实现过程中提出一种新算法,将频谱调整转移到IFFT中处理,减少延时,节省存储资源约109Kbit。提出多级CORDIC运算结构,在每级单元中实现一定次数的迭代,以满足更小硬件开销的FFT/IFFT需要。上述新算法和运算结构已成功应用于实际系统中。

This paper presents an implementation for the orthogonal frequency division multiplexing(OFDM) with 2K,4K and 8K three modes.The synthesis and simulation results are given.The radix-2 decimation-in-time algorithm based on 16-bit fixed-point operation and pipeline architecture are adopted in the core module IFFT(Inverse Fast Fourier Transform).In order to avoid fixed overflow and improve the precision,some methods including bit-extension,output-scaling and half adjusting are taken in account.The system performance is emphasized by the improvement on the ratio of the IFFT's output signal to noise,that is 74dB under all three modes.The novel algorithm proposed in the implementation of OFDM can decrease the latency and save 109Kbit memory resource by moving the spectrum-adjustment into IFFT.Moreover,a multi-stage CORDIC operation structure is also proposed to meet FFT/IFFT with low hardware cost by operating some iteration in each unit.The new algorithm and operation structure are already applied in practical systems successfully.