All-standard-cell voltage controlled oscillator-based analog to digital converters with digital background calibrations
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An all-digital voltage controlled oscillator based analog to digital converter (VCO-based ADC) with digital background calibration is proposed in this thesis. The all-digital structure simplifies implementation procedure and reduces design cost. Different structures of all-standard-cell VCOs are presented and compared. This thesis also focuses on improving VCO’s linearity. A novel compensation for all-digital VCO-based ADC is proposed, which uses closed-form orthogonal polynomials bases instead of power series ones. With these more powerful bases, cross interaction between different basis is eliminated, which leads to better resolution, lower order of compensation, and shorter convergence time. Offset-injection digital background calibration for VCO-based ADC is designed based on the proposed orthogonal polynomials nonlinearity compensation. The new technique removes in-band distortions caused by VCO nonlinearity successfully. Tradeoff between different design parameters like sampling frequency and offset value is discussed in the thesis. A smart offset injection technique for all-standard-cell VCO is also introduced.