Analysis of 3-Level Bandpass Sigma-Delta Modulators With 2-Level Output

This brief analyzes a recently introduced, 2-level bandpass modulator incorporating 3-level lowpass ΣΔ modulators. While the combination of 3-level ΣΔ with 2-level output improves output signal-to-noise ratio (SNR) in a wideband sense, it also introduces nonlinear distortion in the 2-level output. In this brief, the nonlinear effects are modeled and a linearization technique offering up to 22 dB of error cancellation is derived. In result, the modified 2-level modulator can show up to 6 dB of an SNR improvement versus equivalent for a 2-level ΣΔ modulator. The new technique is demonstrated through analysis and experimental results.