Research And Implementation Of Delta-Sigma Modulator

The virtue of conventional methods on A/D,D/A with resistance network is their use of a low sampling frequency. As improving resolution on D/A conversion, Conventional converters are often difficult to implement in fine-line very large scale integration technology. A low cost and highly ratio of quality to price is the most important reason for Delta-Sigma modulator. High precise D/A design always put Delta-Sigma modulator to the front end of analog 1-bit D/A conversion instead of conventional converters with resistance network.This paper based on D/A basic theory deeply research on Delta-Sigma modulator's basic structure and noise shape loop theory ,then implementing a 5^th order Delta-Sigma modulator based on this theory .On the 5^th order Delta-Sigma modulator ,We encode coefficients with CSD(Canonic Signed Digit),implement multiplication with shift adding, Reducing the use of adder in this multiplication, and saving almost 10 percent of die area,improving ratio of performance vs price.This is the most important point in the paper.The research content and contribution include :1. Encode the float coefficients of modulator with CSD in the first time, rather than conventional Two's Complement .Except for binary '1,0', additional '-1' was add to binary number representation . Namely represent coefficients with Numbers '-1,0,1'.That's ternary value. Implement multiplication with shift adding, reducing use of adder in this multiplication, so save die area.2. Implementing a 5^th order Delta-Sigma modulator with digital method ;treating 5^th order Delta-Sigma modulator as a noise shape digital filter; count coefficients of modulator with Matlab toolbox, so designing a 5^th order Delta-Sigma modulator with high ratio of performance vs price .3. This design have taped out .Take many methods of verification and analyse in the design.Encode the design with VHDL language and synthesize the design with synopsys company tools Design Compiler. Simulate the design with matlab and delta-sigma toolbox.Count the coefficients with delta-sigma toolbox. Simulate the design with modelsim.Research on theory and result of experiment show: Delta-Sigma modulator with CSD can save die area and improve ratio of performance vs price.Delta-Sigma modulator which is implemented can match oversampling filter with oversampling ratio 32, and there is 80db on ratio of signal vs noise .