KEYWORDS: Antennas, General packet radio service, Dielectrics, Transmitters, Receivers, Transmission electron microscopy, Amplifiers, Signal to noise ratio, Radio propagation, Sensors
Recently considerable efforts are put in development of Ground Penetrating Radar (GPR) systems for detection and identification of the buried artifacts and structures. The GPR performance is associated with the properties of the local soil and buried targets as well as the implementation of its hardware and software. When the aim in conventional GPR systems is detection of objects, some applications require identification of objects. It is necessary a new generation of GPR hardware for the identification of objects. This new hardware should perform highly accurate measurements of the scattered field. In this paper, the development of GPR system for the identification of buried small objects is presented. System covers broad bandwidth more than 2 GHz in order to achieve sufficient down-range resolution. GPR is operated lower frequencies because of technological restrictions of pulse generator. The performance of GPR for buried object detection and identification depends significantly on the ability of the antenna to radiate impulses into the ground without distortion. GPR antennas are operated close to the ground for efficiently coupling the energy into the ground. However this causes antenna characteristics to change as the ground condition changes. This characteristics instability makes it difficult to reduce the antenna clutter in the post processing. A novel broad band GPR antenna was developed over a wide frequency range to improve the stability. This new design was improved from dielectric loaded horn antenna.
While investigating the scattering from vegetation canopy it is necessary to know the scattering-law of electromagnetic waves on some single elements. Some principal problems that arise while studying the electromagnetic wave scattering from single leaf have been formulated in this paper. Two problems can be considered here: the influence of the moisture content and the shap of the leaf upon the scattering characteristic. This study represents some results of the experimental investigation of diffraction properties of vegetation canopy and its elements. These experimental components of the study included measurements of back- scattering cross sections, distribution of electromagnetic field in the near zone and radiation pattern. The measurement has been carried out in the millimeter range.
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