Low profile fully planar folded dipole antenna on a high impedance surface

A fully planar antenna design incorporating a high impedance surface (HIS) is presented. The HIS is composed by a periodic array of subwavelength dogbone-shaped conductors printed on top of a thin dielectric substrate and backed by a metallic ground plane. First, the characteristics of a dipole over PEC or PMC layers, a dielectric slab, and the HIS are compared and studied in detail, highlighting the advantages provided by the use of the HIS. Then, the design of a low profile folded dipole antenna working at 5.5 GHz on top of the HIS is described. The surface provides close to 6% antenna impedance bandwidth and increased gain up to 7 dBi, while shielding the lower half space from radiation. The antenna structure comprises three metal layers without any vias between them, and its overall thickness is 0.059λ 0. The dipole is fed by a balanced twin lead line through a balun transformer integrated in the same antenna layer. A prototype has been built and measurements confirming simulation results are provided. © 2006 IEEE

A low profile folded dipole antenna on a reactive high impedance substrate

We present a fully planar realization of a low profile dipole antenna placed on top of a high impedance substrate. The structure is made by three metal layers and it does not requires vias between the layers. The antenna is matched to 50 Ohms and has a gain of 7.1 dBi including all feed network losses. © 2009 IEEE

Low profile fully planar folded dipole antenna on a high impedance surface

A fully planar antenna design incorporating a high impedance surface (HIS) is presented. The HIS is composed by a periodic array of subwavelength dogbone-shaped conductors printed on top of a thin dielectric substrate and backed by a metallic ground plane. First, the characteristics of a dipole over PEC or PMC layers, a dielectric slab, and the HIS are compared and studied in detail, highlighting the advantages provided by the use of the HIS. Then, the design of a low profile folded dipole antenna working at 5.5 GHz on top of the HIS is described. The surface provides close to 6% antenna impedance bandwidth and increased gain up to 7 dBi, while shielding the lower half space from radiation. The antenna structure comprises three metal layers without any vias between them, and its overall thickness is 0.059λ 0. The dipole is fed by a balanced twin lead line through a balun transformer integrated in the same antenna layer. A prototype has been built and measurements confirming simulation results are provided. © 2006 IEEE

A low profile folded dipole antenna on a reactive high impedance substrate

We present a fully planar realization of a low profile dipole antenna placed on top of a high impedance substrate. The structure is made by three metal layers and it does not requires vias between the layers. The antenna is matched to 50 Ohms and has a gain of 7.1 dBi including all feed network losses. © 2009 IEEE

Seismic Retrofit of r.c. Buildings with Base Isolation

Seismic isolation is today largely used as a passive mitigation system for seismic actions. While this technique can be easily implemented in new structures, more difficult, whenever possible, is the implementation in existing buildings, which can become a real challenge especially in countries where maintenance of old structures, sometimes of historical importance, is an important issue, like Italy. The use of seismic isolation in existing buildings presents interesting features. Using a base isolation system, the period of vibration can be chosen in order to allow input of low spectral amplitude, so that the superstructure can substantially remain in the elastic range. This possibility allows for limiting or even avoiding the conventional retrofit intervention in the superstructure. In fact, the intervention can be concentrated at the lowest level, while no intervention is necessary in the superstructure, so it is not necessary to demolish non-structural elements. As a result, an “operational seismic retrofit” would be possible, that is the superstructure could remain operative during the retrofit works. In order to do that, at least a safety degree not lower than the existing one should be guaranteed. This can be obtained by using temporary fixing systems for the isolation devices or temporary structures for the columns. After a brief overview of the available research in this field, the paper proposes and discusses different solutions for “operational seismic retrofit”, pointing out also the convenience in terms of costs. Furthermore, a case study is presented, in which some solutions are implemented