Experimental Characterization of A Piezoelectric Transducer Array Taking into Account Crosstalk Phenomenon

Ultrasonic transducer arrays are generally composed of several piezoelectric elements arranged in 1D or 2D ways. Crosstalk is an undesirable phenomenon decreasing the performance of these devices. It generates parasitic displacements at the elements' radiating surfaces, which changes the directivity of the array. Furthermore, the transducer's displacement plays a critical role in terms of the focal area and transferred intensities. The objective of this paper is to characterize a piezoelectric array composed of seven-elements made of PZ 27 ceramic experimentally. It investigates the effects of the crosstalk phenomenon on the array's performance in particular. The results have shown that the array's elements vibrate mainly in thickness mode, but the displacement is not uniform along their length due to the contribution of a parasitic length mode. Moreover, the major parasitic displacements are obtained on the neighboring passive elements: about -7.3 dB, -11 dB, and -12 dB, on the first, the second, and the third elements, respectively

Wideband Planar Antenna for New Generation Mobile Applications

A wideband, compact planar monopole antenna having a 2 : 1 VSWR bandwidth of 98% (1.68 GHz–4.9 GHz) is presented. The omnidirectional radiation pattern with moderate gain and linear polarization in the entire band makes the antenna an excellent candidate for new generation mobile applications. Details of the antenna design and a comparison of simulated and measured results are presented and discussed

Investigation of Cross-Coupling in Piezoelectric Transducer Arrays and Correction

Cross-coupling in piezoelectric transducer arrays is an undesirable phenomenon which decreases the performance of these devices. Indeed, when one element of a transducer is driven, it generates parasitic displacement fields at the radiating surfaces of the neighboring elements, which changes the directivity of the array. The objective of this paper is to investigate the cross-coupling effects on the piezoelectric transducer arrays performance and to propose solutions to reduce this parasitic phenomenon. In this context, it is demonstrated that a filling material having high mechanical losses contributes to the reduction of cross-coupling. In addition to this, a procedure of active cancellation of cross-coupling is successfully tested in the case of two transducer arrays vibrating in the transverse mode for the first prototype and thickness mode for the second one. Finally, the ability of the method is demonstrated even when the displacement at the radiating surface of the transducer array is not uniform

Contribution à l'étude et à la correction de la diaphonie dans les réseaux de transducteurs piézoélectriques pour l'imagerie médicale

Que ce soit dans le domaine médical ou en contrôle non destructif, les systèmes d’imagerie ultrasonore sont devenus de plus en plus utilisés de nos jours. Leurs applications ne cessent de s’élargir et des performances toujours plus accrues sont vivement recherchées, afin d’améliorer la qualité des diagnostics réalisés. Nous sommes donc passés de l’utilisation de systèmes à base de transducteurs ultrasonores mono-élément à des systèmes utilisant des réseaux de transducteurs à une dimension (1D) et à deux dimensions (2D) composés d’éléments de plus en plus nombreux et petits. Néanmoins, un phénomène indésirable est fortement présent dans ces réseaux de transducteurs ultrasonores : il s’agit du couplage inter-éléments tendant à limiter leurs performances acoustiques et à modifier leur diagramme de rayonnement. Tout au long de ce travail de recherche, nous avons donc cherché à comprendre ce phénomène parasite et à apporter des solutions pour le réduire voire le supprimer. En se basant sur des modélisations éléments finis 2D et 3D et grâce à la fabrication de prototypes, nous avons d’une part, mis en évidence les différents types de couplages présents dans un réseau de transducteurs (acoustique, mécanique) et d’autre part, deux méthodes de correction basées l’une comme l’autre sur l’application de tensions convenables aux différents éléments du réseau ont été testées. La première méthode utilise les déplacements normaux moyens à la surface de chaque élément du réseau pour évaluer ces tensions, tandis que la deuxième fait appel aux courants motionnels parcourant chaque élément pour les déterminer. Les résultats numériques et expérimentaux concernant les déplacements et les diagrammes de rayonnement sont en bon accord. En outre, les deux méthodes s’avèrent particulièrement efficaces pour réduire le couplage inter-éléments.Whether in medicine or in non-destructive testing, ultrasonic imaging systems have become increasingly used nowadays. Their applications continue to expand and good performances are needed to improve the quality of the diagnosis. Moreover, significant progress has been made since these systems were originally based on single element ultrasonic transducers and are now made of mono-dimensional (1D) and bi-dimensional (2D) elements arrays ever more numerous and smaller. However, an undesirable phenomenon is strongly present in the ultrasonic transducer arrays: it is the cross-talk, which limits their acoustic performances and modifies their radiation pattern. Throughout this research, we have attempted on one hand to understand this parasitic phenomenon and on the other hand to provide solutions in order to reduce it or even remove it. To highlight the cross-talk types (acoustic and mechanical) and to test the proposed correction methods, we developed two-dimensional (2D) and three-dimensional (3D) finite element modeling and fabricated some prototypes. Both correction methods rely on the application of suitable voltages to the array elements. The first method uses the average of the normal displacements at the surface of each element to evaluate the voltages, while the second one utilizes the motional currents through each element to determine them. The numerical and experimental results concerning the displacements and the radiation patterns are in good agreement. In addition to this, both methods have been efficiently performed to reduce the cross-talk

BROADBAND WIDE COVERAGE UNIPLANAR ANTENNA

The Present thesis deals with the numerical as well as experimental investigations conducted on the resonance and radiation characteristics of Drum shaped monopole antenna, Funnel shaped monopole antenna and the shorted coplanar antenna.An introduction to the over view of antennas, state of the art planar antenna technologies, different feeding techniques and introduction of coplanar waveguides have been discussed.Department of Electronics, Cochin University of Science and Technolog

A wideband printed monopole antenna for 2.4-GHz WLAN applications

A planar monopole antenna suitable for broadband wireless communication is designed and developed. With the use of a truncated ground plane, the proposed printed monopole antenna offers nearly 60% 2:1 VSWR bandwidth and good radiation characteristics for the frequencies across the operating band. A parametric study of the antenna is performed based on the optimized design, and a prototype of the antenna suitable for 2.4-GHz WLAN application is presented. The antenna can be easily integrated into wireless circuitry and is convenient for application in laptop computers

Machine learning for predictive maintenance of photovoltaic panels: cleaning process application

It is well known that the presence of dust on the surface of PV modules has a significant impact on their efficiency. Then, the consequent reduction in energy production has a non-negligible effect on the incomes. Although there is a growing need for accurate data showing where the solar arrays need maintenance in this rush for renewable energy. The purpose of this article is to introduce the research on existing photovoltaic panel maintenance solutions and introduce a new machine learning algorithm application to minimize the cleaning process of photovoltaic modules