Oversampling digital-to-analog converters

Oversampling and noise-shaping methods for digital-to-analog (D/A) conversion have been widely accepted as methods of choice in high performance data conversion applications. In this thesis, the fundamentals of D/A conversion and oversampling conversion were discussed, along with the detailed analysis and comparison of the reported state-of-the-art oversampling D/A converters.;The dual-quantization technique developed in the course of this research provides a good alternative for implementing multi-bit oversampling D/A converters. The system uses two internal D/A converters; one is single-bit and the other is multi-bit. The single-bit D/A converter is used in a path called the signal path while the multi-bit D/A converter is used in a path called the correction path. Since the multi-bit D/A converter is not directly placed in the signal path, its nonlinearity error can be noise shaped by an analog differentiator so that the in-band noise contribution from the nonlinearity error is very small at the system output, greatly reducing the linearity requirement on the multi-bit internal D/A converter.;An experimental implementation of an oversampling D/A converter using the dual-quantization technique was carried out to verify the concept. Despite about 10 dB higher noise than expected and the high second-order harmonic distortion due to practical problems in the implementation, the implemented system showed that the corrected output had more than 20 dB improvement over the uncorrected output in both signal-to-noise ratio and dynamic range, demonstrating the validity of the concept.;Conventional oversampling D/A converters use 1-bit internal D/A conversion. Complex analog filters and/or large oversampling ratios are usually needed in these 1-bit oversampling D/A converters. Using multi-bit internal D/A conversion, the analog filter can be much simpler and the oversampling ratio can be greatly reduced. However, the linearity of the multi-bit D/A converter has to be at least the same as that required by the overall system.