Antisaturation Carrier Tracking Technique for Ground-Based Positioning Systems

As an alternative to global navigation satellite systems (GNSS), ground-based positioning systems (GBPS) can achieve high-precision positioning based on carrier phase measurements in GNSS-denied environments. However, due to a large dynamic range of the received signal power in GBPS scenarios, the receiver front-end is susceptible to saturation when processing strong signals from nearby base stations (BS). In such cases, conventional tracking technique may suffer from a significant carrier phase tracking error and degraded ranging performance, which results in a limited carrier phase positioning range and reduced practicality of GBPS. To this extend, this paper proposes an antisaturation carrier tracking technique based on Fourier series (FS) decomposition, which comprises a saturation detector, a multiharmonic predetection filter and a multiharmonic carrier phase discriminator. Compared to the conventional technique, it can extract sufficient carrier phase information from those excessively strong GBPS signals distorted by front-end saturation. Numerical simulation results demonstrate that, except in cases with low saturation levels and minimal carrier Doppler frequencies, a superior carrier tracking performance can always be obtained. Results of a wireless experimental test further validate the effectiveness of the proposed technique. Therefore, more accurate and reliable carrier phase ranging and positioning can be achieved when the receiver is very close to a BS, thereby expanding the usable positioning range of GBPS and enhancing its practicality and robustness.