Limitations of the VCO-Based Quantizer

In the following sections, both quantizers are compared in the presence of circuit nonidealities such as VCO nonlinearity, phase noise, and sampling clock jitter. These nonidealities are added to the VerilogA model, and theoretical equations are derived to verify the effects on each quantizer. Although the FDC has been widely adopted due to its inherent first-order noise shaping characteristic, the noise shaping is shown to degrade in the presence of phase noise and clock jitter. Other circuit nonidealities exist but are ignored in this analysis since these quantizers are highly digital circuits.