Ultra Wideband Transient Scattering and Its Applications to Automated Target Recognition

Reliable radar target recognition has long been the holy grail of electromagnetic sensors. Target recognition based on the singularity expansion method (SEM) uses a time-domain electromagnetic signature and has been well studied over the last few decades. The SEM describes the late time period of the transient target signature as a sum of damped exponentials with natural resonant frequencies (NRFs). The aspect-independent and purely target geometry and material-dependent nature of the NRF set make it an excellent feature set for target characterization. In this chapter, we aim to review the background and the state of the art of resonance-based target recognition. The theoretical framework of SEM is introduced, followed by signal processing techniques that retrieve the target-dependent NRFs embedded in the transient electromagnetic target signatures. The extinction pulse, a well-known target recognition technique, is discussed. This chapter covers recent developments in using a polarimetric signature for target recognition, as well as using NRFs for subsurface sensing applications. The chapter concludes with some highlights of the ongoing challenges in the field

GPR prospecting in a layered medium via microwave tomography

The tomographic approach appears to be a promising way to elaborate Ground Penetrating Radar (GPR) data in order to achieve quantitative information on the tested regions. In this paper, we apply a linearized tomographic approach to the reconstruction of dielectric objects embedded in a layered medium. The problem is tackled with reference to a two-dimensional geometry and scalar case when data are collected over a linear domain with finite extent. In particular, in order to increase the amount of independent available data, a multi-frequency/multi-view/ multi-static measurement configuration is considered. With reference to stepped-frequency radar, this means that for each working frequency and for each position of the transmitting antenna (moved along a linear domain), the electric field scattered by the buried targets is measured in several locations along the same linear domain. The proposed inversion approach is based on the Born approximation and a regularized solution is introduced by means of the Singular Value Decomposition (SVD). The problem of determining the optimal measurement configuration (in terms of number of frequencies and number of transmitting and receiving antennas) is also tackled by a numerical analysis relying on the Singular Value Decomposition (SVD). Numerical examples are provided to assess the effectiveness and robustness of the proposed approach against noise on data

“Unlocking” the Ground: Increasing the Detectability of Buried Objects by Depositing Passive Superstrates

One of the main problems when trying to detect the position and other characteristics of a small inclusion into lossy earth via external measurements is the inclusion’s poor scattering response due to attenuation. Hence, increasing the scattered power generated by the inclusion by using not an active but a passive material is of great interest. To this direction, we examine, in this work, a procedure of “unlocking” the ground by depositing a thin passive layer of conventional material atop of it. The first step is to significantly enhance the transmission into a lossy half space, in the absence of the inclusion, by covering it with a passive slab. The redistribution of the fields into the slab and the infinite half space, due to the interplay of waves between the interfaces, makes possible to determine the thickness and permittivity of an optimal layer. The full boundary value problem (including the inclusion and the deposited superstrate) is solved semi-analytically via integral equations techniques. Then, the scattered power of the buried inclusion is compared to the corresponding quantity when no additional layer is present. We report substantial improvement in the detectability of the inclusion for several types of ground and burying depths by using conventional realizable passive materials. Implementation aspects in potential applications as well as possible future generalizations are also discussed. The developed technique may constitute an effective “configuration (structural) preprocessing” which may be used as a first step in the analysis of related problems before the application of an inverse scattering algorithm concerning the efficient processing of the scattering dat

UAV for Landmine Detection Using SDR-Based GPR Technology

This chapter presents an approach for explosive-landmine detection on-board an autonomous aerial drone. The chapter describes the design, implementation and integration of a ground penetrating radar (GPR) using a software defined radio (SDR) platform into the aerial drone. The chapter?s goal is first to tackle in detail the development of a custom-designed lightweight GPR by approaching interplay between hardware and software radio on an SDR platform. The SDR-based GPR system results on a much lighter sensing device compared against the conventional GPR systems found in the literature and with the capability of re-configuration in real-time for different landmines and terrains, with the capability of detecting landmines under terrains with different dielectric characteristics. Secondly, the chapter introduce the integration of the SDR-based GPR into an autonomous drone by describing the mechanical integration, communication system, the graphical user interface (GUI) together with the landmine detection and geo-mapping. This chapter approach completely the hardware and software implementation topics of the on-board GPR system given first a comprehensive background of the software-defined radar technology and second presenting the main features of the Tx and Rx modules. Additional details are presented related with the mechanical and functional integration of the GPR into the UAV system