Higher order spectral analysis of nonlinear behavior in Σ-Δ modulator

Higher order spectral properties of Σ-Δ sequences are studied. For this purpose a first-order single stage Σ-Δ modulator is considered having as input a pure sinusoid. The nonlinear behavior of the Σ-Δ modulator is examined by means of the bispectrum and the bicoherence. These functions reveal the statistical properties of the quantization noise, its dependence on the signal as well as the phase coupling between the signal and the noise. The quantizer and the integrator of the Σ-Δ modulator have been studied, using different functions, to simulate the deviations from the ideal behavior.