Second-order delta-sigma modulation with interfered reference

A delta-sigma (ΔΣ) modulator has been traditionally analyzed by assuming its reference to be constant, but practically the reference may be interfered and thus vary with time. For an interfered reference modulator, the performance of quantization noise is degraded by quantization noise leakage due to interfered feedback. In this paper, a systematic study for observing the behavior of a second-order modulator with an interfered reference is presented, based on linear modeling, spectral analysis, and behavioral simulations. An analytical form of the output of a ΔΣ modulator with an interfered feedback is obtained and compared with behavioral simulation. Due to the agreement between the theoretical calculation and the behavioral simulation results, it is concluded that the quantization noise leakage should be considered for describing the behavior of ΔΣ modulators more precisely