<FONT face=Verdana>A new structure of GPS carrier tracking loop is proposed based on maximum likelihood estimation. The loop is used for tracking GPS carrier frequency under the circumstance of high dynamic and low signal-to-noise ratio. Details of the loop are presented in this paper

and the functions of all the blocks in the loop as well as parameter transmission among the blocks are discussed. Performance of the loop is tested using GPS carrier signals with typical high dynamic parameters. Results of the tests indicate that the designed loop greatly improves the loss-of-lock threshold and frequency tracking precision near the threshold compared with the ones in common GPS receivers.