Direct Digital Synthesizers Theory: Design and Applications

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Direct Digital Synthesizers Theory: Design and Applications

Best Regards for the efforts of the author for development of IC

Helsinki University of Technology
Department of Electrical and Communications Engineering
Electronic Circuit Design Laboratory

Direct Digital Synthesizers: Theory, Design and Applications
Jouko Vankka
November 2000

Abstract
Traditional designs of high bandwidth frequency synthesizers employ the use of a phaselocked-
loop (PLL). A direct digital synthesizer (DDS) provides many significant advantages
over the PLL approaches. Fast settling time, sub-Hertz frequency resolution, continuous-phase
switching response and low phase noise are features easily obtainable in the DDS systems. Although
the principle of the DDS has been known for many years, the DDS did not play a dominant
role in wideband frequency generation until recent years. Earlier DDSs were limited to
produce narrow bands of closely spaced frequencies, due to limitations of digital logic and D/Aconverter
technologies. Recent advantages in integrated circuit (IC) technologies have brought
about remarkable progress in this area. By programming the DDS, adaptive channel bandwidths,
modulation formats, frequency hopping and data rates are easily achieved. This is an
important step towards a “software-radio” which can be used in various systems. The DDS
could be applied in the modulator or demodulator in the communication systems. The applications
of DDS are restricted to the modulator in the base station. The aim of this research was to
find an optimal front-end for a transmitter by focusing on the circuit implementations of the
DDS, but the research also includes the interface to baseband circuitry and system level design
aspects of digital communication systems.
The theoretical analysis gives an overview of the functioning of DDS, especially with respect to
noise and spurs. Different spur reduction techniques are studied in detail. Four ICs, which were
the circuit implementations of the DDS, were designed. One programmable logic device implementation
of the CORDIC based quadrature amplitude modulation (QAM) modulator was
designed with a separate D/A converter IC. For the realization of these designs some new
building blocks, e.g. a new tunable error feedback structure and a novel and more cost-effective
digital power ramp generator, were developed.
Keywords: Direct Digital Synthesizer, Numerically Controlled Oscillator, GMSK Modulator,
Quadrature Amplitude Modulation, and CORDIC algorithm

Table of Contents
PREFACE .................................................................................................................................II
ABSTRACT ............................................................................................................................. III
TABLE OF CONTENTS ........................................................................................................ IV
LIST OF ABBREVIATIONS ...................................................................................................X
LIST OF SYMBOLS............................................................................................................ XIII
1. INTRODUCTION ..................................................................................................................1
2. DIRECT DIGITAL SYNTHESIZER ...................................................................................8
3. INDIRECT DIGITAL SYNTHESIZER.............................................................................18
4. CORDIC ALGORITHM.....................................................................................................23
5. SOURCES OF NOISE AND SPURS IN DDS....................................................................33
6. BLOCKS OF DIRECT DIGITAL SYNTHESIZER.........................................................48
7. SPUR REDUCTION TECHNIQUES IN SINE OUTPUT DIRECT DIGITAL
SYNTHESIZER.......................................................................................................................63
8. UP-CONVERSION...............................................................................................................79
9. DIRECT DIGITAL SYNTHESIZER WITH AN ON-CHIP D/A-CONVERTER..........87
10. CMOS QUADRATURE IF FREQUENCY SYNTHESIZER/MODULATOR...........101
11. MULTI-CARRIER QAM MODULATOR ....................................................................115
12. SINGLE CARRIER QAM MODULATOR...................................................................135
13. MULTI-CARRIER GMSK MODULATOR..................................................................142
14. CONCLUSIONS...............................................................................................................167
REFERENCES .......................................................................................................................169
Appendix A : Fourier Transform of DDS Output ...............................................................189
Appendix B : Derivation Output Current of Bipolar Current Switch with Base Current
Compensation.........................................................................................................................190
Appendix C : Digital Phase Pre-distortion of Quadrature Modulator Phase Errors.......191
Appendix D : Different Recently Reported DDS ICs ..........................................................193


[ 本帖最后由 alvays 于 2007-3-29 19:09 编辑 ]

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