Evaluation of the stability of phase difference measurement in a passive bistatic GNSS radar system based on a software receiver

The passive bistatic radar method using signals of global navigation satellite systems reflected from the Earth's surface can be used to determine and monitor various geophysical parameters of the reflecting surface. Most receiver architectures for this method are based on specialized hardware receivers, but software-defined radio (SDR) technology is rapidly evolving and allows real-time signal processing. This allows to develop a bistatic GNSS-reflectometry system on its basis. The article analyzes that the use of a software receiver will allow receiving and processing existing and future signals of all navigation satellite systems. Experiments with various parameters of different software receivers have been conducted, which have shown the stability of the phase difference between the receiving channels. It is shown that for some types of software receivers, a significant improvement in the measurement error of the phase difference is observed when synchronizing from an external highly stable reference generator.