Abstract
An arbitrary waveform generator (AWG) using Direct Digital Synthesis (DDS) technique was investigated in this thesis. Conventional DDS suffers from high level of spurious frequencies in the output spectrum caused by the quantization errors. In this paper, we simulate, compare and do performance evaluation of several popular spur reduction techniques, including modified Nicholas phase accumulator, Non-subtractive dither, Subtractive dither techniques, etc. It is found that the second-order random phase dither has the best performance in SFDR regarding phase truncation error and the random amplitude dither has the best performance regarding the amplitude quantization error. To reduce the hardware complexity and cost while maintaining good performance, a modified 1-bit MLBS based dither method was proposed to reduce the spurs in the DDS. Several FPGA-based AWG cards with ISA interface were built for experiments. We had also finished a PC-Based virtual instrument for controlling the AWG. LabWindows was used in constructing the user-friendly virtual instrument. Users can control the waveform, frequency and phase of the AWG output signals by system control interface. It also can display the output signals in user's PC by GPIB interface. Some experiments were also conducted to compare performances of our system and HP 3325, HP 33120.