Enhanced Tracking with Improved Code Autocorrelation Function via Fractional Fourier Domain

Over the last half-century, the positioning performance of global navigation satellite system (GNSS) receivers has significantly improved from hundreds of meters to sub-meter accuracy or higher. This progress primarily relies on the expanded satellite numbers and satellite navigation constellations as well as the enhanced emitted satellite navigation signal designs. However, advancements on the GNSS receiver design side have been minimal. For example, as the core of a GNSS receiver, the baseband processor predominantly uses fast Fourier transform (FFT) and convolution/correlation calculations, a common understanding within the GNSS receiver community. This reliance has led to bottlenecks in current receivers, particularly in providing robust multipath and interference mitigation and achieving high-accuracy navigation and positioning in challenging environments such as dense urban. This work introduces an elevated baseband processor based on the fractional Fourier transform (FRFT) theory to address these issues. We propose a chirp-signal-modulated code convolution procedure to upgrade GNSS receiver tracking thoroughly. Advantages of the proposed code tracking architecture in the fractional Fourier domain (FRFD) include but are not limited to accelerating the code rates of received spreading codes and extending current code tracking from a one-dimensional (1D) code-phase/time domain to a two-dimensional (2D) FRFD. Simulation results have demonstrated the superior tracking accuracy of the proposed architecture compared to classic architecture. Our work has the great potential to revolutionize commercial satellite navigation receivers and overcome the limitations faced by current commercial integrated circuits and modules in challenging environments.