Signal acquisition has become the performance bottleneck of global navigation satellite systems (GNSS) receivers in harsh interference environments due to its low sensitivity. In this Letter, a novel antijamming algorithm based on the minimum mean square error criterion is proposed to protecting the acquisition stage. The key idea behind the proposed method is that the grid search process of synchronisation parameters is shared by both interference suppression and signal acquisition. Simulation results indicate that the proposed method is capable of maintaining the functionality of GNSS receivers at cold start in the presence of interfering signals. In addition to this, its performance outperforms the power inversion method significantly.

In precise relative positioning applications, an effective approach to improve the interoperability of GNSS systems is the tightly combining or inter-system double-differencing of observations from the common frequencies that are shared by different constellations. As the BeiDou satellites are currently transmitting a B2 signal at 1207.14 MHz that is identical to the Galileo E5b signal, the inter-system double-differenced observations can also be created between observations from both systems at that particular frequency. In this paper, we will focus on the instantaneous ambiguity resolution performance analysis of tightly combining BeiDou B2 and Galileo E5b observations. The size and stability of phase and code Differential Inter-System Biases (DISBs) between BeiDou B2 and Galileo E5b signals are first investigated, in which the new BeiDou and Galileo satellites launched recently will also be included. Then, first results of the Tightly Combined Model (TCM) with a priori corrected DISBs (TCM_C) are evaluated in comparison to the Loosely Combined Model (LCM) and tightly combined model with unknown DISBs (TCM_F) in an instantaneous approach. It is demonstrated that the instantaneous integer ambiguity resolution performance can be improved using the TCM_C with respect to LCM and TCM_F.

Power-inversion (PI) adaptive arrays are widely used in Global Navigation Satellite System (GNSS) receivers for interference mitigation. The effects of element patterns on the performance of PI adaptive arrays are investigated in this paper. To this end, the performance of adaptive arrays is investigated by Monte Carlo simulations, using CST Microwave Studio (Dassault Systems, Vélizy-Villacoublay, France) to calculate the radiation patterns of circular microstrip elements which are used to compute the adaptive weight and the adaptive array gain. It is shown that the performance of PI adaptive arrays is mainly dependent on the gain pattern of the reference antenna element rather than the non-reference elements because the algorithm essentially pushes the elements into an unequal position. Furthermore, the results show that the impact of mutual coupling on the performance of the antenna array can be associated with the radiation patterns of the reference element, which is helpful in selecting the optimum reference element without increasing computational complexity, especially for small GNSS arrays.

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The endless spoofing interference affects the credibility of the navigation system seriously. In order to suppress the forward spoofing which is more threatening to military signals in GNSS, this paper proposes a spoofing suppression algorithm based on angle of arrival estimation and multi-satellite fusion. On the basis of successfully suppressing the spoofing signal, the algorithm improves the estimation accuracy of the angle of arrival of the forwarded spoofing and reduces the attenuation of the carrier to noise ratio of the real satellite signal. Finally, the effectiveness of the algorithm is verified by simulation, which has guiding significance for the anti-spoofing research of GNSS.