Band-stop noise modulated bandpass sigma-delta analog-to-digital converter

In this paper, we present a method to reduce the effects of substrate noise on bandpass sigma-delta (SigmaDelta) ADCs through the use of band-stop noise modulation, where the notch of the modulation noise spectrum is centered around the input signal band. Several band-stop noise (BSN) resonator structures required for bandpass SigmaDelta ADC implementations are presented. The proposed designs have been adapted from traditional resonator designs. These include the forward Euler (FE) resonator, forward Euler non-delayed (FEND) resonator, lossless discrete integrator (LDI), and the double-delay resonator. An example utilizing a fourth-order BSN modulated bandpass SigmaDelta ADC with a 1-bit quantizer is presented. Additionally, a method to generate the required BSN sequence is proposed. Simulation results demonstrate that this architecture achieves a 7.7 dB improvement in SNR and a 19 dB improvement in SFDR over the traditional fourth-order bandpass SigmaDelta ADC