软件无线电中直接波形合成的研究

直接数字频率合成（DDS）是一种新型的频率合成技术。介绍了如何利用DDS技术来产生调频波形及其他的数字调制波形；阐述了一种新的适合于软件无线电实现的算法，即采用预先计算后存贮在贮存器中的波形来代替实时运算，直接合成数字调制波形（DWS）；研究了一种压缩查找表的方法。此外，还对此算法在实现过程中遇到的截断误差、运算量和存贮量的问题进行了探讨。对于所提及的算法，给出了仿真结果。

Research of DWS in Software Radio System

The technique of direct digital synt hesis(DDS)is a novel frequency synthesis tech-nique.This paper introduces how DDS techniques can be extended to produce frequency modulated(FM)waveforms as well as many types of dig itally modulated waveforms.Then,A new transmit architecture of these algorithms in a software radio system is proposed that emphasizes t he use of pre -computed wave-forms stored in memory instead of rea l -time computation to directly generate digitally modulated wave-forms (DWS ).And we also do some research on compr essed look -up tables.Furthermore,the effects of truncating the response of the transmit filter as well as memory versus computation is introduced.As to the modulation methods discussed in the paper,simulation results are provided.