C/N₀ Estimator Based on the Adaptive Strong Tracking Kalman Filter for GNSS Vector Receivers

The carrier-to-noise ratio (C/N) is an important indicator of the signal quality of global navigation satellite system receivers. In a vector receiver, estimating C/N using a signal amplitude Kalman filter is a typical method. However, the classical Kalman filter (CKF) has a significant estimation delay if the signal power levels change suddenly. In a weak signal environment, it is difficult to estimate the measurement noise for CKF correctly. This article proposes the use of the adaptive strong tracking Kalman filter (ASTKF) to estimate C/N. The estimator was evaluated via simulation experiments and a static field test. The results demonstrate that the ASTKF C/N₀ estimator can track abrupt variations in C/N and the method can estimate the weak signal C/N correctly. When C/N jumps, the ASTKF estimation method shows a significant advantage over the adaptive Kalman filter (AKF) method in terms of the time delay. Compared with the popular C/N algorithms, the narrow-to-wideband power ratio (NWPR) method, and the variance summing method (VSM), the ASTKF C/N estimator can adopt a shorter averaging time, which reduces the hysteresis of the estimation results.