调频信号的数字合成方法

调频信号作为一种常见信号在电子技术的各个领域，特别是通信领域有着广泛的应用。因此调频信号的合成就成为了其中关键性的一项技术。传统的调频信号通常是通过模拟方法合成的。但是模拟合成有频率不稳定、参数设置不可量化等缺点，而用数字合成的方法就可以解决这些问题。数字频率合成通常采用DDS技术，调频信号的数字合成也基于这项技术。本文首先介绍了DDS的基本原理。然后提出用双DDS结构实现调频信号数字合成的方法。由于把调制波形的幅度量化成了频率字，构成了一个输出频率字的DDS。因此只要改变这个DDS波形RAM中的数据。就可以产生任意以周期信号为调制波形的调频信号，并且调制频率和深度都精确可调。

The Method of Digital Synthesis of FM Signals

FM signal, as a kind of common signal used in many areas of electronic technique, especially finds extensively its use in communications system. The synthesis of FM signals is reasonably regarded as one sort of key technique. Traditional synthesis of FM signals can usually be implemented with the help of using analog methods, but those ways have some disadvantages of being unstable frequency, being unable to quantize parameter settings. By comparison, it can avoid those drawbacks by using digital methods. The synthesis of digital frequencies usually employs the technique of DDS which digital synthesis of FM signals is also based on.This paper first presents the fundamentals of DDS, and then gives a method of accomplishing digital synthesis of FM signals by means of dual DDS structures. These DDS correspondingly become what consist of outputting words of frequencies due to quantizing the input waveform. Consequently, as far as changing data in DDS RAM, we can freely get FM signals modulated with any-periodic waveforms in addition to adjusting modulating-frequency and depth accurately.