Abstract
A novel adaptive approach for sigma-delta modulators (SDMs) to improve dynamic range significantly is proposed. Based on adapting the signal power gain of SDMs, several dynamic-range curves can be obtained. The cascade of integrators with distributed feedback (CIFB) structure is used to demonstrate the basic idea. A systematic approach with the proposed optimising algorithm is used to acquire the boundary constraints. Therefore, a wider dynamic range can be achieved without changing the original architecture. The simulation results reveal that the proposed method under coefficient spread of 60 000 can improve dynamic ranges by 39 and 20 dB for a fourth-order CIFB structure with an oversampling ratio (OSR) of 32 and 64, respectively. Moreover, a fourth-order SDM with CIFB structure and OSR of 32 under the coefficient spread of 3 455 with less hardware is implemented by switched-capacitor circuits, and a 16 dB dynamic range improvement is revealed to agree with the proposed method.
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