Sigma-delta Modulation And The Class D Amplifier

The subject, Sigma-Delta Modulation (SDM) and D-class Amplifier, is from Shanghai Fangtek Electronics Co., Ltd. (www.fangtek.com.cn), and is studied there. This subject belongs to the basic theory study, whose aim is to understand the corresponding theories and to prepare for IC design. IC prototype based on PCB (Print Circuit Board) is designed, too. The subject has two parts. One belongs to digital circuit (SDM), and the other is analog part (D-class Amplifier). As a matter of fact, SDM is a closed-loop control system, which follows the input signal and embeds the information of input signal in the low-frequency part of output-1-bit stream. The high-frequency part of 1-bit stream is filtered out while low-frequency part is remained when the 1-bit stream is used to drive a speaker. So, The information of input signal will be rebuilt on the speaker. SDM has 4 theoretic keys. The first is over sampling. The second is noise shaping. The third is stability and the last is the model of quantizer. Simple linear quantizer model can be used to analysis over sampling and noise shaping, and can be used to design modulator based on large amount of simulation, too. But, it cannot analysis stability correctly. So, nonlinear model of quantizer should be studied. To discuss the theoretic keys of SDM and the problems related with D-class Amplifier in detail can be viewed as the contribution of this thesis. It makes a better understanding of SDM and D-class Amplifier, and comes up with the corresponding design rules. The theoretic analysis relies on not only computer simulation, but also hardware emulation based on FPGA.