Oversampling Sigma-Delta Modulator Stabilized by Linear Sliding Mode Control Technique

In view of the features of "finite-time control" and "variable structure system" techniques in the area of control system theorem, this paper utilizes a simpler linear "sliding mode control" (SMC) technique to raise the stability of high-order sigma-delta modulator (SDM). The proposed linear SMC technique not only suppresses the output swing range of all critical integrators effectively, but also avoids the instability limitation of high-order SDM without SNR degradation. This is because the stabilization scheme of the proposed technique leads the output states of all critical integrators to approach the sliding surface promptly and stay within sliding mode steadily, and keeps the overall operation constant through a digital compensative loop. The SIMULINK simulations verify that both stability and dynamic range of SDM can also be improved a lot by this simpler linear SMC technique.