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Seeking to increase the autonomy of wireless sensing devices, this article analyzes different RF rectifier topologies for ambient energy harvesting applications at 2.45 GHz, focusing on scenarios where the input received power level of the RF rectifier is between -10 dBm and -20 dBm. For this propose, an equivalent diode RF model is taken into account for better describing the diode effect on the efficiency of each rectifier topology, presenting the impedance curve of four commercial diodes, and the respective conducting thresholds, without loss of generality. Furthermore, a computational rectifier optimization methodology is given, discussing the relation of the load impedance with the resulting circuit efficiency.

This paper presents a solar cell coplanar patch antenna designed to operate in the 2.4 GHz band. The simulation results were validated by the solar cell antenna’s prototype fabrication and characterization. The proposed antenna has a gain of $4.13 \mathrm{dBi}, 15.14 \%$ bandwidth, and efficiency of $87.1 \%$ at 2.45 GHz. Also, the I-V curves of the solar cell were extracted for indoor irradiation levels. The $I_{S C}$ and the $V_{O C}$ were $2.35 \mathrm{~mA}$ and 135 mV, respectively, supplying $100 \mu \mathrm{W}$ in the maximum power point. The satisfactory results endorse the operability of the prototype for simultaneous operation as solar energy harvesting and radiator element.

The Ocean Color 2 (OC2), Ocean Color 3 (OC3) and Dall'Olmo three-band (TBDO) algorithms used for the estimation of the chlorophyll-a concentration [Chl-a] have been calibrated and validated for Sentinel-2 spectral bands. Measurements of in situ chlorophyll-a, radiometry and simulations with HydroLight have been used for this purpose within the Ecological Status of AQuatic Systems Satellites (ESAQS) Project to estimate water quality in aquatic systems in Spain. The results show that Sentinel-2 spectral bands are suitable for studying the chlorophyll-a concentration in inland waters. The TBDO algorithm have been applied to Sentinel-2 images and satisfactory results have been obtained in Albufera of Valencia region (Spain).

This paper will analyze the CLL (Capacitively Load Loop) structure applied on the cave form on the patch plane surface of a planar UWB (Ultra Wide Band) antenna. The purpose is to improve the features of the antenna for application in the new generation of WLAN (Wireless Local Area Network). Simulations were done with the insertion of the metamaterial in several distinct configurations. It will be presented the results in which there was a superior efficiency compared to the basic antenna without modifications.

An application of active inductors in a CMOS LNA with inductive partial degeneration in 0.35µm technology is presented. Both, the inductor of the partial degeneration and the output load inductor, are actives. The results are satisfactory, validating the compact design and demonstrating the technical feasibility of this design for use in several electronic RF devices.

In this paper we propose a cluster-based approach for the delineation of management zones in precision agriculture. The proposed approach was built following the steps of data mining for the clustering task, resulting in a computer application that generates maps of management zones and yield areas, allowing to compare them using known statistical indexes. The basis for this implementation was a model previously published in the literature that uses only historical productivity, soil electrical conductivity and relief data to generate the maps. The main difference of our work with respect to the previous model is the clustering algorithms used in the step of extracting patterns. While the original model uses only the fuzzy c-means algorithm, the model developed in this study uses the GKCluster extension to this algorithm, able to detect clusters with different geometrical shapes. From the tests performed with the new proposed model, we achieved about 76% of correlation between maps of yield and management zones from kappa index, and about 85% of correlation from overall accuracy. The original model reached, according to the authors, a maximum correlation of 49% from kappa index, and 70% from overall accuracy.