This chapter presents the research done by authors in recent years on microstrip antennas and their applications in wireless sensors network. The subject is delimited to the study of conventional microstrip antennas, from which antennas with fractal and polar shapes are proposed. A detailed description of the antenna design methodology is presented for some prototypes of microstrip antennas manufactured with different dielectric substrates. Analysis of the proposed antennas has been done through computational simulation of full-wave methods. Experimental characterization of antennas and dielectric materials has been performed with the use of a vector network analyzer. The results obtained for the resonant and radiation parameters of the antennas are presented. Computer-aided design (CAD) of microstrip antennas and arrays using fractal and polar geometrical transformations results in a wide class of antenna elements with desirable and unique characteristics, such as compact, exclusive, and esthetic antenna design for multiband or broadband frequency operation with stable radiation pattern.
This paper presents the characterization of dielectric properties (dielectric permittivity and dielectric loss factor) of Tommy Atkins mango (Mangifera indica L), a fruit produced in several regions of Brazil, of great economic importance. The fruits were characterized according to their maturation index, by probe method, and identified by the yellowish tone in their bark. The results allowed correlating the dielectric characteristics of the fruit with the physicochemical transformations that occurred in the maturation process of the mango Tommy. It was also verified a greater variation in the frequencies below 1 GHz, with the maturation indicated by the dielectric signature on the fifth day after the harvest. From these results, we can observe the use of electromagnetic materials and techniques in the solution and optimization of processes in agriculture can improve the quality of products consumed or suggesting best practices to the productive sector.
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