Improving the Design of Frequency Lock Loops for GNSS Receivers

An analysis of the design and performance of the discrete-update GNSS frequency lock loop (FLL) is presented. Expressions for the design and the steady-state performance of one first-order and two second-order FLL loop filters are developed. Transient performance of the FLL in the presence of thermal noise is examined and the relative performance of four carrier frequency discriminators is studied. It is shown that careful discriminator choice can yield a 10 dB performance improvement relative to "naive" designs.