The Design And Verification Of The Sigma-Delta Modulator

In the21st century, with the rapid development of science and technology, portable digital devices have become an integral part in people’s daily life. Designed with high efficiency, high quality audio amplifiers, you can continue to push toward high-fidelity digital devices, miniaturization, multi-functional direction.Power amplifiers play an important role in the audio system. And they directly related to the audio system’s sound quality, efficiency, power consumption, size and other properties of the good or bad. Because class D amplifier works is rather special, it has only two states on and off, so people call this amplifier "digital power amplifier " Compared with the traditional A class, B class, AB class power amplifier, D power amplifier have significant advantages: high efficiency (90%), low power consumption, small size, simple manufacturing processes and so on. So, in the background of green, class D power amplifier has been widely applied.Modulator is an important part of class D power amplifier and plays an important role in analog-digital conversion. The D class power amplifier which based on∑-△modulation has significant advantages:distortion smaller, more efficient and less susceptible to electromagnetic interference.Firstly, class D power amplifier∑-△modulation is analyzed theoretically in this paper. Established a∑-△modulator order "simple cascade structure" model, and derive the SNR and the modulator order, over sampling ratio as a function of type. Taking into account the existence of various nonlinear factors, we can introduce feedback to make the∑-△modulator work stably. This is the model of∑-△modulator which is called "Cascade-of-resonators, feedback form (CRFB)".Based on theoretical analysis, I designed the structure of a6-order CRFB∑-△modulator and simulate by using Simulink and then verify the stability. The waveform is consistent with the theoretical analysis. Finally, I used the Verilog HDL to describe the circuit and then I used FPGA to verify.The results of the simulation and verification show that the modulator has a high signal to noise ratio (about110dB) and well stability. At the same time, it takes fewer resources and has the advantages of simple. Overall, it has a certain practical value.