Application Note

RF Signal Record & Playback System for GPS Testing and Validation

The ability to record a real-world signal for hours on end has substantial implications for today’s RF test engineers. By recording the signal, it is possible to capture a wide range of channel impairments, such as large-scale channel fading, multi-path propagation, and interference. In this scenario, an RF recording system is taken on a drive test through an environment that is known to be particularly difficult for receivers. Then, once a large amount of data is captured (a few hours or more), the recorded signal can be re-generated in a lab environment and directly connected to the receiver itself. Use of recorded waveforms for Global Navigation Satellites System (GNSS) receiver testing has many advantages over traditional test methods. First, when compared to GNSS simulators, this method enables more natural impairments as opposed to simulations. Thus, receivers can be tested with a rich and realistic set of data, including SBAS signals associated with the atmospheric error at the time of recording. Second, it also produces test results that are perfectly repeatable.