The Method of Digital Synthesis of FM Signals
Wu Sha · Information Technology and Informatization · 2006
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.