A carrier tracking loop with series-connection structure is proposed to solve the tracking problem of carrier signal.The loop's universal phase model is established in Z domain to analyze its tracking performance in the case of AGWN(Additive Gauss White Noise) input

and a general formula is derived for calculating variance of phase tracking noise.The theory analysis results are verified via a specific instance of new loop.Based on the above analysis results

the loop's optimization and the comparison between the traditional and the proposed loop are done

which shows that the proposed is superior to the traditional loop under the condition of high dynamic and very low CNR (Carrier to Noise Ratio).The conclusion can be used to evaluate the receiver's tracking performance or design loop.