OFDM技术及其在短波通信中的应用

正交频分复用是采用多信道数字调制，将数据经编码后调制为射频信号的技术。在短波信道中应用OFDM技术，利有Ⅳ路子载波，在相同数据传输速率下，码元周期延长N倍，远大于信道的延时，从而消除码间串扰。各子载频之间满足正交条件，使信号频谱可重叠，提高频谱利用率，并有良好的频率分集效果，能抗多径强窄带干扰。为进一步克服码间串扰的影响，一般利用计算IDFT时添加一个循环前缀的方法，在OFDM的相邻码元间增加一个保护间隔，使相邻码元分离。

OFDM Technologies and Applications in Shortwave Communication

OFDM （Orthogonal Frequency Division Multiplexing） technology uses multi-channel digital modulation, after coding, data were modulated as radio-frequency signal technologies. Applying OFDM technology in the short-wave channel, while adopting N way sub-carr, the period of code element would be N times longer under same data transmission speed, which is much greater than the channel retardation, thus code disturbances could be eliminated. Satisfying orthogonality conditions among each carrier frequency could make signal spectrum overlapped, therefore improve the spectrum availability. The nice frequency diversity effects could resist disturbance of multipath wide and narrow band. Moreover, in order to overcome code disturbances, add a circular prefix during IDFT calculation, and add a protection interval between border code elements, hereby the two code elements could be parted.