Influence of oscillator variations on the observed frequency behavior in software-based navigation receivers

This letter discusses the effects of oscillator behavior such as phase and frequency offsets on the observed frequency behavior in software-based receivers. Frequency errors introduced by the front-end oscillators and sample clocks cause the observed frequency to differ from the actual frequency. Frequency errors directly affect the user velocity and position estimates in navigation receivers unless these errors are explicitly estimated and removed. This letter will show the derivation of a quantitative relationship between the observed frequency and the true frequency of the received signal in the presence of local oscillator and sample rate errors.