说明：  这个程序用于生成OFDM信号和它的频谱，对于初学者迅速掌握OFDM的生成机制特别有帮助。Matlab版本: R13
(This process used to generate the OFDM signal and its spectrum, for beginners to master the rapid formation mechanism OFDM particularly helpful. Matlab version: R13)