Quality evaluation of the pulse per second (PPS) signals from commercial GNSS receivers

Abstract

GNSS receivers are often integrated with other sensors such as inertial navigation system (INS) and camera. The pulse per second (PPS) signal from GNSS receiver is commonly used as the benchmark for time synchronization with other sensors, which is crucial for the accuracy of the sensor integration. Therefore, the timing quality of the PPS signal is important and worthy to be evaluated comprehensively. We use a chip scale cesium atomic clock to evaluate the PPS quality of three popular commercial GNSS receivers. A practical evaluation method is proposed, which can mitigate the systematic error of the reference clock effectively. The PPS interval stabilities are evaluated by Allan variance to reflect the PPS time offset, and the clock divergences during GNSS signal loss are measured to reflect the capability to maintain the clock accuracy. The test results show that with nominal GNSS satellite signal condition, the standard deviations of the PPS intervals are in the order of 10E−8 s, and the maximum clock offset after 10 min of losing lock is at microsecond level. The qualities of the PPS signal from the tested receivers are sufficient for the time synchronization of the integrated navigation systems.