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In this paper, the development of an ultra-wideband (UWB) array-based time-domain radar sensor for near-field imaging is described. The radar sensor is designed to be used within a vehicle-mounted multisensor system for humanitarian demining. The main novelty of the radar lies in the system design with a single transmitter and multichannel receiver. Design of the UWB antenna array is also novel. The radar produces 3-D images of subsurface by 1-D mechanical scanning. The imaging capability of the radar is realized via electronic steering of the receive antenna footprint in a cross-scan direction and synthetic aperture processing in an along-scan direction. Imaging via footprint steering allows for a drastic increase in the scanning speed. Index Terms--Ground penetrating radar (GPR), landmine detection, near-field imaging, ultra-wideband (UWB) antenna array.

The two-arm, conical spiral antenna (CSA) is a well-known antenna that has several desirable features when isolated in free space, such as uniform input impedance, gain, and circular polarization over a broad frequency range. In this paper, this antenna is investigated when placed directly over the ground with its axis normal to the surface of the ground. In this configuration, the CSA may be useful for applications in which signals must be transmitted into the ground and/or received from within the ground, such as communication links to underground tunnels and ground-penetrating radars. First, the performance of the CSA in free space is briefly reviewed, and then qualitative arguments based on the geometrical and electrical properties of the isolated antenna are used to predict the performance when this antenna is placed over the ground. Next, results from a complete analysis of the CSA over the ground, performed with the finite-difference time-domain method, are used to quantitatively verify these predictions. The paper ends with an illustrative example in which the CSA is used in a monostatic ground-penetrating radar. Index Terms--Broad-band antenna, conical spiral antenna (CSA), finite-difference time-domain (FDTD), frequency-independent antenna, ground-penetrating radars (GPR).

A new modification of the TEM-horn antenna has been developed for ground-penetrating radar (GPR) applications. The antenna is based on a dielectric wedge, and thus, was named the dielectric wedge antenna. Tapering of the metal flairs has been used to match the antenna to the ground and to reduce the late-time ringing. The finite-difference time-domain model of the antenna has been created to investigate physical processes within the antenna and to optimize its performance. The dielectric wedge antenna has shown a superior (in comparison with the TEM-horn) performance by radiation in different types of the ground and has been used in a novel antenna configuration within a GPR system, which is dedicated for landmine detection. Index Terms--Finite-difference time-domain (FDTD), ground penetrating radar, TEM-horn antenna, transient antenna, ultra-wideband antenna.