Novel Time-Interleaved variable-center frequency Σ-Δ modulators-design, analysis and critical evaluation

This paper presents the design, analysis and system level modeling of two novel multi-path discrete-time Σ-Δ modulators that can accomplish noise-shaping for any center frequency from DC to Nyquist. The proposed topologies are well-suited for Butterworth, Chebyshev and Inverse Chebyshev loop-filters offering designers the flexibility of specifying the center-frequency, pass-band/stop-band attenuation as well as the signal bandwidth. The topologies are compared in terms of their signal-to-noise ratios, hardware complexity and immunity to nonidealities. Extensive simulations verify that one of the examined topologies not only uses fewer coefficients but also exhibits greater robustness to non-idealities.