採離位雙振幅調變之離散多頻調變的波型設計

Abstract

離位頻域分散多工和離散多頻調變的差別在於其在時域上使用了較平滑且長度較為延長的濾波器，以期降低正交信號之間的旁波帶。這裡，在使用離位雙振幅調變為調變方式的架構下，找出最佳化的傳送和接收濾波器。而這些濾波器在時域和頻域中皆存在相互重疊的特性；藉由它們，系統可實現極佳重建，也就是說不會有符際和頻道間的干擾出現。另外，因為我們以具連續性質的cubic splines組成濾波器，所以也可提供類比型態的濾波器。

OFDM (orthogonal frequency division multiplexing) differs from DMT (discrete multitone) by the use of time domain shaping and duration extension to reduce the spectral sidelobes of the orthogonal signal set. Here we optimize the transmit and receiving filters with offset QAM modulation. The filters overlap in both the time and frequency domains. And they can achieve perfect reconstruction without inter-symbol and inter-channel interference. In addition, because we compose the filters by cubic splines with the continuous property, an analog waveform is expectable.