POLITECNICO DI TORINO
School of Information Engineering
Graduation in Electronic and Computer Engineering

Bachelor of Science Thesis

Design and Realization of a low cost Signal Generator by means of Direct Digital Synthesis

Supervisor: Prof. Marco Parvis Eng. Simone Corbellini

Candidate: Rodrigo Alves da Silveira

July 2010

To my family

Introduction

Introduction
Electronics in the past few decades have evolved in a way that mankind could never imagine, making it possible to achieve technologies that would completely re-design their way of life. With each new discovery, it comes an uncountable number of new possibilities. That is the way Electronics works, always being reinvented in order to attend the needs of …ver más…

DDS provides remarkable frequency resolution and allows direct implementation of frequency, phase and amplitude modulation. These features which were 'tacked-on' to function generators now are handled in a clean, fundamental way by DDS. The designed signal generator will be able to synthesize arbitrary waveforms. Its frequency, phase and amplitude will be digitally adjustable by the user. In order to do, some key components are need: a DDS, which needs only an external clock to generate simple sinusoidal waves, a DAC (Digital to Analog converter) and an operational amplifier, these last two combined, will control the amplitude. Figure 1.1 shows an abstract diagram of the system.

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Chapter 1 – The Signal Generator Project

Amplitude Regulator

USER PC

Microcontroller

DDS
Offset Regulator

Output

Figure 1.1 – Abstract block diagram of the signal generator

In the following chapters a more detailed description of all the blocks and its functions will be given.

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Chapter 2 – The Direct Digital Synthesis

Chapter 2 The Direct Digital Synthesis
DDS devices are programmed through a high speed serial peripheral-interface (SPI), and need only an external clock to generate simple sinusoidal waves. The today’s devices can generate frequencies from less than 1 Hz up to 1000 MHz (AD9912) [1].

2.1 The reasons for using DDS
The benefits of their low power, low cost, and single small