Over-sampling Of The Audio Signal Processing And Conversion

This thesis researched the audio signal process based on delta-sigma principle. It includes the design of audio DAC, ADC and power amplifier (PA). The△∑DAC is composed of interpolator, digital△∑modulator and the analog back-end circuit. The△∑ADC is composed of analog△∑modulator and decimator. The analog△∑modulator can be used to implement the audio Class D power amplifier as well.Delta-sigma structure is a popular choice in the design of high precision data converter. But it consumes large area and great power. To cut down its cost of area and power, some novel methods are proposed in the thesis.To cut down the interpolator's and decimator's hardware, the FIR filter as a tapped cascaded interconnection of identical sub-filters is researched in the thesis.Today power DAC has become a trend that the audio DAC is integrated with PA and drives the load directly. Here a novel 1.5-bit power DAC structure is proposed where a filterless Class D switches with feedback loop is used to implement power amplification. The output of the△∑modulator is 1.5bit which depresses greatly the high frequency power loss caused by the filterless Class D switches. The feedback loop improves the circuit's anti-jamming ability. The proposed power DAC has remarkable advantages over traditional structures in area and power consumption.In this thesis, a novel analog△∑modulator structure is proposed as well. Its first stage is a continuous-time integrator, and the other stages are switch-capacitor (SC) integrators. Then the modulator combines these two integrators' respective advantages and obtains the trade-off between the circuit area and output performance. The analog△∑modulator can be shared by audio ADC and audio Class D.To silicon-certificate the above-mentioned ideas, a power DAC an ADC and a Class D are designed. The ADC and the Class D share one analog△∑modulator. The power DAC is implemented with TSMC 0.18μm process. The die area is 0.5mm~2. Its output dynamic range exceeds 100dB. The total harmonic distortion (THD) is less than -80dB. The Maxim SNR in-band is higher than 90dB. With 8Ωload, the maxim output power of the power DAC is 436mW. The ADC and the Class D are implemented with TSMC 0.35μm process. The die area is 1mm~2. The dynamic range of the ADC exceeds 100dB. The THD and SNR in-band of the Class D are -92dB and 90dB respectively. With 8Ωload, the maxim output power of the Class D is 514mW.All the measured performances are according to the design targets.