Calibration of RFI Detection Levels in a Low-Cost GNSS Monitor

The Global Navigation Satellite Systems (GNSS) is an invaluable tool that is heavily used in everyday life across numerous industries. Despite their ubiquitous use, GNSS signals are very vulnerable to both intentional and unintentional forms of radio frequency interference (RFI). This paper supports the development of a low-cost GNSS RFI monitor that can reliably enhance a user's spatial awareness with respect to the state of RFI in their local environment. Multiple jamming experiments are conducted using an anechoic chamber to analyze the response of three different receivers to both wide band and narrowband forms of jamming. The power level of the jamming signal is varied to show how changes affect recorded metrics in the receiver. Specifically, the automatic gain control (AGC), the carrier-to-noise power density ratio (CNO), spectrum, and position information are valuable in understanding the receiver's state. These results provide a reference for calibrating low-cost receivers when monitoring for interference.