Numerical methods are essential to understand tribological behaviors since it is difficult to measure directly a closed contact or write representative analytical equations. In this paper, a focus on the complexity of a contact is done with the modeling of thermo-mechanical phenomena in connection with tribological triplet (mechanism, first bodies, third body). Discrete element method is chosen to have a dynamic view of a contact and is interesting to represent both damage of first bodies and cohesion of third ones. Thermo-mechanical models are described for first and third-bodies and are adjusted as a function of continuity of the body. Results regarding damage, rheology and thermal effects are studied as a consequence of cohesion of third body and applied energy by the mechanism (pressure, velocity). Because mechanical and thermal behaviors have a narrow but unclear relationship, a balance between local energy (cohesion of third body) and global energy (applied forces by mechanism) is recommended.

Abstract-This paper presents the design and fabrication of a coplanar waveguide (CPW) rectenna using a sequential modular approach. The rectenna is printed on high permittivity, low-loss board ARLON AD1000 ( r = 10.35 and tan δ = 0.0023 @ 10 GHz). The rectifier section is realized with a single reverse-biased schottky diode SMS-7630 in reverse topology for which a diode model is obtained at −20 dBm for frequencies F 0 = 2.45 GHz and 2F 0 = 4.9 GHz. The low-pass filter and the impedance matching are synthesized from passive CPW structures. Co-simulation technique is used to overcome CPW simulation limitations and to integrate the diode characteristics. The antenna consists of a circular slot loop antenna with stub matching such that its input impedance is close to 50 Ω. The goal of this work is to design a rectifier to simplify and speed up the fabrication process of a rectenna array. We reduced the number of processes to etch the rectifier on the board and minimized the number of lumped elements. At −20 dBm, simulation of the rectifier with an ideal impedance matching network shows rectification at 2.45 GHz with efficiency of 12.8%. The rectifier and rectenna show efficiency of approximately 10% at an operating frequency of 2.48 GHz.

Abstract. This paper proposes an experimental study of the coupling effect of a rectenna array. The rectifying antenna consists of a compact and efficient rectifying circuit in a series topology, coupled with a small metamaterial-inspired antenna. The measurements are investigated in the X plane on the rectenna array's behavior, with series and parallel DCcombining configuration of two and three spaced rectennas from 3 cm to 10 cm. This study shows that the maximum efficiency is reached for the series configuration, with a resistive load of 10 kΩ. The optimal distance is not significant for series or parallel configuration. Then, a comparison between a rectenna array with non-optimal mutual coupling and a more traditional patch rectenna is performed. Finally, a practical application is tested to demonstrate the effectiveness of such small rectenna array. IntroductionWith the development of very low-power wireless system, numerous researches have focused their attention on the feasibility of powering devices through the harvesting of ambient electromagnetic energy [1]. The main challenges in far field nondirective powering are a result of the low and variable power densities available at the receiving antenna.Therefore, the study deals with the design, optimization and experimental characterization of a compact metamaterial-inspired antenna coupled with a rectifier. Then, to increase DC power over the load, the proposed rectenna has been interconnected to form arrays [2]. This is called DC-combining configuration where the outputs of each rectenna are combined in series, parallel or a hybrid manner. It has the advantages to ease the construction of the rectenna array oppositely to the RF-combining configuration. In RF-combining structure, the RF outputs of each antenna are combined before the rectifier circuit. The RF-combining configuration implies the use of sub-circuit to deal with power leakage and phasing between the antennas. This issue is eliminated when DC-combining is used, but the drawbacks of such configuration are lower RF-to-DC conversion and the use of several rectifying elements.In this paper, we investigate the rectenna array's behavior using electrically small antenna. First, we inquire the effect of mutual coupling on two different DC-combining configurations, series and parallel for a finite number of elements. Then, a comparative study is conducted between a rectenna array and a single rectenna using a conventional patch antenna [3], with the same physical surface area. Last, an application of the rectenna array is tested, where a battery-less temperature sensor is powered over a distance of one meter.

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This work deals with the design and implementation of a planar and compact antenna realized on Arlon AD1000 substrate, εr=10.35. The antenna consists of a CPW fed circular slot loop antenna with two stubs as impedance matching circuitry. The antenna was designed for 2.45 GHz in order to be implemented with a RF/DC rectifier optimized for low power level in CPW technology. Thus, allowing easy and fast fabrication of a rectenna array with a high reproducibility between one rectenna conception to another one.