Doppler rate measurements in standard and high sensitivity GPS receivers: Theoretical analysis and comparison

Due to the capability of GPS to provide an accurate and stable long-term reference, the use of a GPS receiver as an acceleration sensor has gained an increasing research interest. GPS-derived acceleration information is determined using Doppler rate measurements that are directly estimated from the output of a Frequency Lock Loop (FLL) or obtained by double-differentiating the carrier phase observations produced by a Phase Lock Loop (PLL). This paper presents a complete theoretical model allowing the evaluation of the Doppler rate accuracy and relating the variance of Doppler rate measurements to the Carrier-to-Noise density power ratio (C/N₀) and the receiver architecture. Both standard and High Sensitivity (HS) receiver architectures are considered and the developed theoretical model is validated using live GPS data. Empirical results are compared against the developed theoretical model and, in all cases, a good agreement between empirical and theoretical results is observed.