A Model of Spurs for Delta-Sigma Fractional PLLs

摘要

In this brief, a model of spurs for fractional PLLs based on Delta-Sigma modulators is presented. The model predicts both fractional and reference spurs and is applicable for modulators of any order. The accuracy of the model is verified by using a conventional second-order modulator for a 2.4 GHz PLL. The results show fair match between the predicted and simulated values with maximum error of 7 dB. The derivation does not consider any spur cancellation or compensation technique.