The Development of a High Performance Digital RF Transmitter for NMR

Abstract

This Master’s thesis consists of the development of a Nuclear Magnetic Resonance (NMR) Radio Frequency (RF) transmitter, which is a core electronic subsystem of an NMR system. The main purpose of this research is to contribute to the application of NMR, which is a new sensing technology that has yet to be fully implemented into the everyday world. One of the barriers to adopting this technology is its complexity. However, the invention of high speed digital FPGAs (Field Programmable Gate Array) such as the Spartan series has made it easier to develop high performance NMR systems over recent years. The major contribution to this research is the development of faster digital signal processing hardware, and methodologies that have been implemented on a single chip. This has reduced the size and the cost of the electronic subsystem and contributed towards the evolution of NMR as a general tool. This thesis introduces the concept of implementing a high-speed NMR RF multi-frequency transmitter by using multiple Direct Digital Synthesis (DDS) cores to generate sine-waves, which range from 100 kHz to 750 MHz. The research required three stages to be achieved, beginning with conceptual design of a high-speed transmitter using MATLAB-Simulink, RTL-level (Register-Transfer Level) simulation and hardware implementation, which included hardware testing on a prototype board. This Master’s research is to seek a solution to building a multi-core DDS module in an FPGA device. In other words, the research work focuses on finding an alternative solution to constructing a DDS system. The project involves building up the VHSIC Hardware Description Language (VHDL) program to work beyond the hardware limitation of an FPGA device. Hence, the final solution does not consider any noise impact due to the structure of the developed system.</p