Direct Digital Synthesis: A Flexible Architecture for Advanced Signals Research for Future Satellite Navigation Payloads

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Direct Digital Synthesis: A Flexible Architecture for Advanced Signals Research for Future Satellite Navigation Payloads, Is A Well-Researched Topic, It Is To Be Used As A Guide Or Framework For Your Research

Abstract

In legacy Global Positioning System (GPS) Satellite Navigation (SatNav) payloads, the architecture does not provide the exibility to adapt to changing circumstances and environments. GPS SatNav payloads have largely remained unchanged since the system became fully operational in April 1995. Since then, the use of GPS has become ubiquitous in our day-to-day lives. GPS availability is now a basic assumption for distributed infrastructure; it has become inextricably tied to our national
power grids, cellular networks, and global nancial systems. Emerging advancements of easy to use radio technologies, such as software-dened radios (SDRs), have greatly lowered the diculty of discovery and exploitation of vulnerabilities to these systems.

The promise of a Direct Digital Synthesis (DDS) architecture provides the exibility of incorporating countermeasures to emerging threats while maintaining backward capability with existing GPS signals. The objective of the proposed research is to determine if DDS architecture is a viable replacement for legacy GPS SatNav payloads. The overall performance
of several architectures is analyzed and evaluated. The architecture with the best performance is chosen and implemented onto a programmable logic device, and GPS signals are generated. The advantages and disadvantages of using the DDS model are discussed and an end-to-end numerical and mathematical models are developed.

The end-to-end mathematical model analyzes the quantization eects of the DDS architecture, and it predicts the location and power levels of the desired signal and spurious content present in the spectrum. The spurious content may potentially cause intermodulation distortion to the desired signal. The appropriate DDS architecture and resources are selected by the information gained from the mathematical model.

Table of Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
List of Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii
I. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
II. Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 DDS Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.1 Pulse Output DDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.2 Fractional Divider DDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.3 Triangle Output DDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2.4 Sine Output DDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.5 Phase Interpolation DDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.6 Wheatley Random Jittering Injection DDS. . . . . . . . . . . . . . . . . . . 10
2.3 GPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3.1 History of Transit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3.2 History of TIMe/navigATION (TIMATION) . . . . . . . . . . . . . . . . . 13
2.3.3 History of System 621B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.4 History of GPS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4 GPS Payload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.5 GPS Signal Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.6 Hardware Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.6.1 High-Speed digital-to-analog converter (DAC) . . . . . . . . . . . . . . . . 22
2.6.2 L1 Reconstruction Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.6.3 Field Programmable Gate Array (FPGA)
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
III. SatNav Flexible Architecture Testbed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.1 Digital System Architectures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.2 DDS Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.3 Parallel Pipeline Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.4 Verication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

IV. Phase Noise and Quantization Eects and Modeling . . . . . . . . . . . . . . . . . . . . 40
4.1 Phase Noise Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.1.1 Data Collection Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.1.2 Phase Noise Verication Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.2 DDS and Mathematical Modeling of Quantization
Error and Eects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.2.1 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.2.2 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.2.3 DDS Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.2.4 Mathematical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.3 Results of DDS and Mathematical Model Quantization
Eects and Mathematical Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.4 End to End Results of Phase Noise and Quantization of
the System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.4.1 Phase Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.4.2 Quantization Error Eect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
V. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.1 SatNav Flexible Architecture Testbed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.2 Phase Noise and Quantization Eects and Modeling . . . . . . . . . . . . . . . . . 74
5.2.1 Examination of Phase Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.2.2 Quantization Eects and Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.3 Publications and Technology Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.4 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
vii