Process tolerant design of N-tone ΣΔ converters

An N-tone ΣΔ converter is obtained by introducing N zeros in the noise transfer function (NTF) while maintaining a flat signal transfer function (STF). N-tone ΣΔ converters are particularly well suited for multi-carrier systems. Like low-pass and band-pass ΣΔ converters, the performance of this converter depends heavily on the resonator characteristics. Non-idealities in the resonator manifest themselves as a deterioration in the signal to noise ratio (SNR). In this paper, we study different implementations of N-tone ΣΔ converters. We look into the various sources of non-idealities in the converter and their impact on system SNR. Using our understanding of the impact of nonidealities, we present a capacitor mismatch insensitive design for N-tone ΣΔ converters.