Clock Errors Simulation and Characterisation

An accurate and correct characterisation of clock errors is of paramount importance for design, simulation, and selection of the suitable equipments for satellite transmitters and receivers in GNSS systems. In this paper, an advanced statistical approach to generate clock errors that fits the real oscillator behaviour is presented. This method has been successfully implemented in different Deimos Space’s applications, including GNSS receiver simulators, analysis tools, and GNSS ground segment facilities. These software tools have especially hard requirements in terms of accuracy in the replication of the clock behaviour and computational load for parallel simulation of several processes. Starting from the power spectral density of the clocks, the Allan standard deviation is obtained and characterised taking into account the different types of noise that are identified in the error figures of an oscillator. Sequences of timing errors are then obtained using random numbers generators and recursive equations. Using these results as inputs, an algorithm to obtain the parameters of the clock model from a given time response is also presented in this paper.