Design and simulation of bandpass delta sigma modulator

• Main Authors: Lin, Yung-Ta, 林勇達
• Other Authors: Wu-Shiung Feng
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/06889176136170262598

碩士 === 國立臺灣大學 === 電機工程學系 === 85 === This thesis focuses on the design of bandpass delta sigma modulator. A design flow of the delta sigma modulator is introduced. Some researches show that the transfer function has effects on the modulator performance. We present the effects by MATLAB simulation. The two-bit fourth-order bandpass delta sigma modulator is first simulated by SWITCAP2 and completes its design by HSPICE simulation. A new bandpass modulator based on the two-delay loop resonator is designed. The two-delay loop resonator is implemented by time- multiplexed integrators. Half of numbers of OP amps, ratio independent in-phase and quadrature branches are achieved in our modulator.For a two-bits quantizer and a two-bit feedback DAC, some other problems appear. The errors of the DAC level has tremendous degradation on the modulator, and effects of the DAC errors are simulated by SWITCAP2 simulator. To eliminate effects of the DAC errors, some approaches are introduced, and individual level averaging approach is chosen. A DAC with individual level averaging is proposed. The improvement of SNR by applying individual level averaging approach is also shown by SWITCAP2 simulator. Simulations of the two-bit fourth-order bandpass delta sigma modulator complete with the HSPICE simulation. The design ends by implementing the modulator in a single chip to be fabricated.