Direct Waveform Synthesis for Software Radios

This work presents results that show how direct digital synthesis (DDS) techniques can be extended to produce frequency modulated (FM) waveforms as well as many types of digitally modulated waveforms, such as PSK or QAM. We show how digitally modulated waveforms can be efficiently synthesized from tables of pre-computed samples. This work also reports on the implementation of these algorithms in a software radio system. I. Introduction The technique of direct digital synthesis (DDS) is gaining popularity as a method of generating sinusoidal signals in digital systems [5]. This technique is especially well suited to software radio systems implemented on architectures which use general purpose processors (GPPs) because these systems often have large amounts of main memory available for storage of pre-computed output samples. These systems can therefore provide great flexibility in the type of waveforms which can be generated. The algorithms developed below show how DDS techniques can b..