Stability improvement of delta-sigma modulator by sliding mode control theory

A delta-sigma modulator is one of systems used for an analog-to-digital converter. It is known that high signal-to-noise ratio will be obtained by making a high-order loop filter of the delta-sigma modulator. However, when input amplitude becomes large, a problem that the system becomes unstable occurs. As measures of the problem, the authors applied the sliding mode control theory to a delta-sigma modulator. A stability of a delta-sigma modulator improved without dropping signal-to-noise ratio by designing a switching hyperplane and a sliding mode controller. The effectiveness of the proposed method is confirmed by computer simulations.