Array-Based Ground Penetrating Synthetic Aperture Radar on Board an Unmanned Aerial Vehicle for Enhanced Buried Threats Detection

Abstract

The usage of unmanned aerial vehicles (UAVs)based ground penetrating radar (GPR) systems has gained interest over the last years thanks to advantages over ground-based systems, such as contactless inspection and capability, to reach difficult-to-access areas. The former is of paramount importance concerning the detection of buried threats, such as improvised explosive devices (IEDs) and landmines. Current state-of-the-art UAV-based GPR systems are able to provide centimeter-level resolution thanks to the use of GPR-synthetic aperture radar (SAR) processing techniques. One of the challenges to keep improving these systems is the scanning throughput, that is, the area that can be scanned in a given time. This contribution presents an array-based GPR-SAR system for subsurface imaging, aiming at maximizing the scanning throughput without jeopardizing the imaging capabilities of the system. First, the antenna array is mounted on a portable setup to evaluate its performance and imaging capabilities. Next, the antenna array is integrated into the UAV platform, and the UAV-based GPR-SAR system with the array is tested in realistic scenarios with different kinds of buried targets. Results show that the scanning throughput is significantly improved and, furthermore, the coherent combination of all transmitting-receiving channels of the array provides enhanced detection capabilities.

Comparison of Scanning Strategies in UAV-Mounted Multichannel GPR-SAR Systems Using Antenna Arrays

“…The first UAV-based prototypes employing more than one RX antenna have been presented in [23] (performing 3D scanning with 1 TX and 2 RX) and in [24] (performing a single forward-backward sweep with 1 TX and 3 RX). A multichannel UAV-mounted GPR-SAR system was recently presented in [25]. However, the integration of antenna arrays on board UAV-mounted GPR systems is still a heavily understudied research topic.…”

“…In particular, this study aims to test scanning strategies which provide a trade-off between the inspection time and the desired detection performance. For that purpose, the same antenna array configuration employed in [25], which comprises 3 TX and 4 RX antennas integrated into a UAV, is considered. In particular, two scanning strategies are compared by means of theoretical analysis, measurements in a controlled environment, as well as measurements of the actual UAV-mounted multichannel GPR-SAR system.…”

Improved Methods for Fourier-Based Microwave Imaging

“…An additional advantage of introducing the field radiated by the Tx/Rx antennas in the imaging algorithm is that it allows for relaxing the sampling rate requirements. This is of particular interest for MIMO-SAR imaging systems [4,[18][19][20], as it allows for increasing the spacing between measurements beyond the Nyquist sampling rate (λ/4 for monostatic systems). It also overcomes some of the limitations of compressed-sensing-based sub-Nyquist imaging [8,21], like the high computational cost or the need for a non-uniform sampling of the acquisition domain.…”