Design and evaluation of time-interleaved variable center-frequency sigma-delta modulators

In this paper, a procedure for the design of time-interleaved variable center-frequency sigma-delta modulator is developed and presented. The proposed sigma-delta modulators will be suitable for high performance data conversion in Global Navigation Satellite Systems applications. By the application of this method, different orders of a generalized multi-path topology that can operate at any arbitrary center-frequency from DC to Nyquist are constructed using delayed-resonators. This topology is well-suited for Butterworth, Chebyshev and Inverse-Chebyshev loop-filters, where designers have the flexibility of specifying the center-frequency, attenuation parameters as well as the bandwidth. Detailed simulations are performed at the behavioral level using non-idealities such as non-unity gains and leaky resonators and their effects on the signal-to-noise ratios are evaluated.