A new approach to the design of low-sensitivity high-resolution bandpass Σ-Δ A/D converters

It is well known that Σ-Δ A/D converters having complementary signal and noise transfer functions exhibit high signal-to-quantization-noise ratios (SQNRs) and high dynamic ranges (DRs), but that they tend to be overly sensitive to capacitor mismatches (potentially leading to unstable converter operation) in a corresponding switched-capacitor (SC) hardware implementation. Recently, a new class of Σ-Δ A/D converters was developed based on magnitude-squared or magnitude complementary signal and noise transfer functions to decrease the sensitivity to capacitor mismatches at the expense of slightly lower SQNRs and DRs. This paper is concerned with the development of a novel approach to the design of Σ-Δ A/D converters. This approach combines the transfer function complementarity (in the overall frequency band) with signal and noise transfer function magnitude complementarity (in the signal passband) to obtain a single Σ-Δ A/D converter with a cascade-of-resonators configuration. Consequently, the resulting A/D converters achieve not only high-stability (arising from magnitude complementarity), but also high DR and SQNR (arising from transfer function complementarity) in the SC hardware implementation. A practical application example is given to illustrate the results.