A Novel Doppler Rate Estimator Based on Fractional Fourier Transform for High-Dynamic GNSS Signal

Abstract

When the fractional Fourier transform (FRFT) is introduced into the weak and high-dynamic global navigation satellite system (GNSS) signal acquisition, the 2-D search cell will be transferred to a 3-D one with respect to the code chip, the Doppler shift, and the Doppler rate. The proper determinations of the code bin and Doppler shift bin in the acquisition process have already been covered in the previous researches. The aim of this paper is to provide an exhaustive analysis of the approach to specify an optimal FRFT order bin, in terms of the Doppler shift rate. The lower and upper bound of FRFT order ranges is determined by the incoming signal dynamics. Then, we propose a precise model to yield an optimal FRFT order bin. Besides, a novel and fast Doppler estimator based on the non-linear least square (NLS) method is presented to improve the performance of the digital FRFT implementation. Finally, an alternate search procedure is proposed to reduce the singular estimations of the NLS method. The simulating examples demonstrate the performance of the proposed algorithms. It has been verified that the computation efficiency and the estimation accuracy have been significantly improved by proposed techniques. INDEX TERMS Global navigation satellite system (GNSS) signal, linear frequency modulation (LFM), fractional Fourier transform (FRFT) order, acquisition, Doppler rate, non-linear least square (NLS).

Research on Time-Correlated Errors Using Allan Variance in a Kalman Filter Applicable to Vector-Tracking-Based GNSS Software-Defined Receiver for Autonomous Ground Vehicle Navigation

“…It is worth noticing that such application towards increasing the performance of the dynamic GNSS signal processing is also embraced with great significance for some aerial system applications, e.g., mapping with unmanned aerial system [43] and airborne radiometric surveys [44]. Some advanced techniques have been recently presented to deal with the these challenging signals [32,45,46]. The vector tracking (VT) technique is capable of remarkably improving the performance on the GNSS signal processing in weak and dynamic environments with the assistance of the position and velocity solutions.…”

A Super-Resolution Algorithm with FRFT Towards GNSS TOA Estimation for Multipath Channel

“…The integration gain could be severely reduced by this sort of frequency error if it is accumulated over a longer discrete time slot than the usual. The gain reduction with respect to the code crosscorrelation would also become much more critical than the case where a conventional integration process is adopted [5], [6]. In other words, it can be said that the influence of the signal dynamics would be exaggerated in a long coherent integration process.…”

Design and Implementation of Vector Tracking Loop for High-Dynamic GNSS ReceiverDesign and Implementation of Vector Tracking Loop for High-Dynamic GNSS Receiver

“…The latter two can be improved on the hardware-design level [ 3 ], but the first needs to be improved on the software and algorithmic levels, which are the focus of this paper. There are many proposed methods on how to achieve high-dynamic signal tracking, such as second-order frequency lock loop (FLL) assisted third-order phase lock loop (PLL) [ 4 ], Kalman filter-based [ 5 ], maximum likelihood-based [ 6 ], and fractional Fourier transform-based [ 7 , 8 ]. However, these methods focus only on a single channel and ignore overall performance.…”