Continuous-Time ΣΔ modulators with VCO-Based voltage-to-phase and voltage-to-frequency quantizers

In this paper, two different VCO-Based quantizers architectures are implemented and compared as multi-bit quantizers of Continuous-Time (CT) Sigma-Delta (ΣΔ) modulator. The first one is the voltage-to-frequency while the second is the voltage-to-phase architecture. Two 4^th order CT-ΣΔ modulators are designed with Voltage-to-frequency and voltage-to-phase quantizers respectively. Both modulators are designed and simulated in 0.13μm technology. The comparision shows that voltage-to-phase quantizer remarkably reduces the VCO non-linearity and increases the modulator's maximum SNR.