In this paper, a dual-band photonics-based radar system used for precise displacement measures in a multitarget scenario is described. The radar was designed for monitoring applications to prevent both structural failures of buildings and landslides. The radar system exploits the technique of stepped frequency continuous wave signal modulation and the displacement of the targets is evaluated through differential phase measurements. In this work, encouraged by the results already achieved in the single-target scenario, we present an investigation extended to the case of multiple targets. We aim to evaluate the accuracy of the displacement estimation both from a simulated and experimental point of view, and to understand how multiple targets impact on the final estimate of displacements. Simulation results demonstrate that it is possible to achieve a typical accuracy of less than 0.2 mm for distances up to 400 m. These results are confirmed by preliminary experimental outcomes, which take into account different operative conditions with multiple targets. Finally, concluding remarks and perspectives draw the agenda for our future investigations.
Figure 1: Yagi3D Antenna.create trough regions in it. The proposed novel Yagi antenna was called Tridimensional Yagi (Yagi3D) and its main properties were analyzed by means of numerical simulations using Ansoft HFSS and experiments. Finally, a prototype was built and experiments on return loss and radiation pattern have been carried out and compared to numerical simulations.II. YAGI3D CONCEPT Yagi3D antenna is a combination of QY and YU antennas. From the first, the microstrip balun is kept, in order to ensure a large bandwidth. The radiant elements (driver and directors), remain similar to those of YU antenna, in other words, cylindrical metal dipoles . The antenna was designed to be fixed to a reflecting plane, which could be a tower, an airplane fuselage or other metallic surface, depending on the applicat ion. Fig. I presents the new Yagi3D antenna, installed in a section of an airplane fuselage, which was used as the reflecting plane for the simulations and experiments. A supporting structure 10 directors is not shown . The resulting construction keeps at the same time features from YU (metal tubes dipoles) and from QY (printed balun) antennas.From a QY antenna designed to operate at P band, initially the amount of substrate used in the balun was optimized to reduce the antenna weight. The borders were reduced and the longer side, which is responsible for the 180 0 phase difference between the microstrip lines, was bent to (b) Model used for simulations, with a reflecting plane.
Balun(a) Antenna without reflecting plane and balun metal box.x Driver z('vAbstract -This work presents the concept and development of the so called Tridimensional Vagi Antenna, which is a novel type of Vagi antenna operating in P band. It was idealized from two other types of Vagi antennas: Quasi-Yagi and Yagi-Uda. The resultant antenna is based on a microstrip balun, as in QuasiVagi, and its driver and directors are made from metal tubes, as in Yagi-Uda, both integrated to a reflecting plane. The key point of this new antenna model is its asymmetric and reconfigurable radiation pattern and therefore the possibility of a high rejection between bands in a plane. This feature was accomplished with the new concept of progressive rotation of directors around driver. We present a design methodology to adjust return loss and radiation pattern characteristics. The final prototype presents 9.4 dB gain at 450 MHz and 47 % bandwidth centered at 425 MHz.
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