GNSS/INS/LiDAR-based Multi-Sensor Fusion (MSF) systems facilitate the efficient integration of multiple navigation sensors to deliver stable and dependable positioning outcomes in Autonomous Vehicles (AVs). Generally, AVs are bound to operate in diverse scenarios. However, state-of-the-art spoofing attack algorithms can identify vulnerable periods of MSF systems and execute aggressive GNSS spoofing in certain specific scenarios with high success rates. The present study proposes a security defense algorithm for MSF systems based on an enhanced Kalman filter, incorporating the Measurement Variance Monitoring (MVM) and Minimum Constraint of Covariance Matrix (MCCM) model. MVM effectively constrains the impact of GNSS signals with large positioning errors, thereby mitigating the adverse effects caused by spoofing attacks. MCCM fully leverages LiDAR information between two consecutive GNSS signals to enhance the credibility of LiDAR measurements, thus improving the positioning correction capability. Furthermore, considering the diverse application environments of AVs, this paper primarily focuses on sensor uncertainty variation and validates different models in varying scenarios. Ultimately, real-world data demonstrate the effectiveness of the proposed anti-spoofing model, which can significantly mitigate positioning errors caused by GNSS spoofing attacks without affecting navigation accuracy.

Nowadays, benefiting from its strong capability of nondestructive detection, the ground-penetrating radar (GPR) has been applied to detect and reconstruct underground targets and has drawn lots of attention both in military and civilian fields. However, in the processing of GPR imaging, due to the dispersion errors caused by random distribution of various particles in soil, conventional imaging methods have disadvantages of low signal-noise ratio (SNR), low resolution, and unbalanced amplitude. In this article, to achieve high resolution and high veracity on underground targets’ 3-D reconstruction, we improved the conventional reverse time migration (RTM) algorithm in perspective of medium constitutive relationship. Besides, we extended the improved RTM method in 3-D environments and reconstructed the 3-D structure of several underground targets. To make the RTM algorithm suitable for stepped frequency continuous wave (SFCW) GPR system, we generated three excitation signal models and analyzed the effect of different excitation signals on imaging performance. Finally, through the quantitative analysis of simulation and on-vehicle experimental results, we found that the 3-D images generated by improved RTM method had higher resolution, smaller measurement error, and higher veracity than those of conventional RTM method.

Hostile spoofing attacks on the Global Navigation Satellite System (GNSS) receiver increase the risk of catastrophic consequences to autonomous driving systems. This paper addresses the problem of vulnerability of Kalman filter (KF) under spoofing attack. A state-of-the-art spoofing attack method based on maximizing the lateral deviation is utilized for verification and analysis. To analyze the vulnerability in actual road scenarios better, an analytic error model of the mechanism of GNSS spoofing is derived. Except for the uncertainty of the initial MSF state, the uncertainty of the uncertainty of Light Detection And Ranging (LiDAR) and the uncertainty of GNSS, a new factor in spoofing attack, the update frequency of different sensors, is investigated in the paper, which in fact is a key factor to increase the immunity Multi-Sensors Fusion (MSF) systems. Experiments were performed in a typical urban scenario of the KAIST dataset. When the update frequency ratio between GNSS and LiDAR is 1, 2, 5, and 10, successful spoof attacks can be performed if the Standard Deviation (STD) of GNSS is smaller than 4m, 2.7m, 1.1m, and 0.7m respectively. Therefore, experiments confirm that the uncertainty of GNSS and the update frequency ratio between LiDAR and GNSS are critical for spoofing attacks, which provides an indication for designing a defense strategy in the future.

An Ultra-wideband Antenna with funnel-shaped slots and rectangle copper sheets loaded was proposed for ground penetrating radar applications covering the frequency range from 250 MHz to 780 MHz. The performances of the proposed antenna were modeled and optimized by using finite difference time domain methods and measured in both time and frequency domains. The proposed antenna had a bandwidth of 102.9% with voltage standing-wave ratio (VSWR) < 2 and a pick gain over 3 dBi, even when the antenna was bent according to the shape of antenna carrier. In addition, a reconfiguration antenna array with switching matrix, which could be loaded up to 12 antennas, was proposed, where the scanning strategy could be programmed according to the requirements. On this basis, the VSWR of antenna array with and without switching matrix were compared, and the performances of bent and non-bent antenna were also compared in the far-field region. For the radiation pattern, the back-lobe level of bent antennas in E-plane was much lower than non-bent antennas, and the main-lobe of bent antennas in H-plane were rotated. For the peak realized gain, although the antenna gain decreases with increasing frequency, the rate of decline of bent antenna gain is significantly less than that of non-bent antenna gain. Finally, the fabricated antennas could be loaded on a SFCW-GPR system for detecting the depth of cable wells under the road.

Step Frequency Continuous Wave Ground Penetrating Radar (SFCW-GPR), as a tool for nondestructive testing of shallow soil surface targets, the realization of the function of SFCW-GPR is mainly based on the theory of refraction, reflection and scattering of electromagnetic wave in the discontinuity of dielectric constant. So, the UWB antenna system, an important part of SFCW-GPR, becomes more indispensable. In this paper, an improved modified universal antenna is designed, simulated and fabricated. Based on a typical Bow-tie antenna, it is modified by the methods of lumped loads, cavity-backed loading and structure loading. The simulated and measured results show that the UWB antenna has 1.36 GHz bandwidth from 0.64 to 2.0 GHz with three resonant wavelength peaks, and having been modified and improved, the UWB antenna performances including voltage standing-wave ratio (VSWR), input impedance, the boresight gain and current distribution, are much better than the typical Bow-tie antenna. In addition, the results of verification experiment of Step Frequency Continuous Wave (SFCW) show that the antenna can be applied to the working scenarios of SFCW-GPR.

In this paper, we propose a coprime array-based technique that enables global navigation satellite system (GNSS) receivers to reliably defend against spoofing attacks with small time-offset. The technique can not only detect spoofing, but also provide direction of arrival (DOA) of the spoofing source. Our approach is implemented on the raw digital baseband signals, hence it does not need to perform the complex despreading and acquisition stage of the GNSS receiver. Crucially, the detector is still available when the number of signals (including spoofing and satellite signals) is more than the number of array elements. The simulation results demonstrate the effectiveness of the proposed technique in terms of DOA estimation and spoofing detection.