Jean-Lou Dubard

3D Voltage Pattern Measurement of a 2.45 GHz Rectenna

In this communication, a fully automatic measurement setup for the voltage distribution of a rectenna in space is reported. This 3D voltage pattern defines the variation of the DC voltage obtained by a rectenna as a function of the direction away from the transmitting antenna. It allows optimizing the placement of the rectenna in the zone of interest. A comparison is performed between the 3D voltage pattern of a 2.45 GHz rectenna and the radiation pattern of the receiving antenna. The results demonstrate that the influence of the rectifier on the radiating part cannot be ignored and validate the need of a 3D voltage distribution measurement to accurately characterize a rectenna system.

TLM computation of temperature distribution in human head exposed to electromagnetic waves

To simulate the temperature elevation in biological tissues exposed to the electromagnetic waves, the thermal aspect must be taken into account by solving the bioheat equation. In this paper, a new numerical scheme based on the TLM method, particularly suitable to highly heterogeneous environments, is applied for computing thermal distribution in a human head exposed to plane wave at 900 MHz. The model was proven to be unconditionally stable which allows using a larger time step than the one involved with FDTD or other TLM models. The numerical results are compared with those simulated with CST.

Rectenna measurement in a realistic environment

Rectennas have received considerable attention in the recent decades thanks to their unlimited applications. In this paper, rectenna measurements in a realistic environment will be investigated. The space diversity technique has been used to mitigate the multipath situation. Two configurations for evaluating the performance of the diversity technique applied to the rectenna(s) were carried out. Especially, two fully automatic measurement setups for RF level and DC level are presented. The measurement system is described with the sleeve dipole transmitting antenna, the movable rectenna receiving system and the configuration of the environment. The reference rectennas operating at 2.45 GHz are presented. The experimental results demonstrate that the output signals of rectennas in the realistic environment fluctuate randomly as a function of their positions, resulting in deep fade of signal quality. By using the space diversity technique, we overcome this phenomenon.

Characterization of a Circular Polarization Microstrip Antenna using a Temporal Method

In this paper, we describe the determination of the characteristics of a very complex circular polarization microstrip antenna using a temporal method. In fact, the entire simulated structure integrates the radiating element and the phase shifter which allows to generate a circular polarization. The main characteristics such as axial ratio, deviation angle of the polarization ellipse are proposed. To validate the simulation, a comparison between the numerical and experimental results is performed. However, the differences between the experience and the simulation can be reduced by improving the spatial discretization of the antenna. Unfortunately, the excessive memory space and time computation of this simulation technique does not allow this. So we propose, at the end of this article that the association of, this simulation technique and the determination of the temporal Greens functions will allow the increased complexity of the studied structure by modelling the various elements which make up the antenna.

Design of compact integrated diodes Pifa rectennas for energy harvesting application

In this paper we propose new compact PIFA rectennas dedicated to the powering of small wireless sensors of low power. The compactness is achieved by removing the filtering and impedance matching circuits and by integrating directly inside the PIFA several Schottky diodes. The optimization of such high integrated and nonlinear radiating structure can be performed only by the mean of a global time domain simulation technique. A Homemade software based on TLM method was then used to design 40×40mm2 PIFA rectennas integrating up to four SMS7630 Schottky diodes. They are capable of harvesting up to 3.67mW DC power in a 3.5kfi load resistor from a plane wave with an extremely low power density of 1μW/cm2 and with a frequency of 2.45GHz.

TLM modeling of thin wires in dispersive media

A new 3-D transmission line matrix-twin wire (TLM-TW) numerical scheme is proposed for modeling thin wires buried in a general inhomogeneous, dispersive, conductive medium. To solve the time convolution product introduced by the dispersive medium, a recursive algorithm obtained by bilinear Z-transform approach is used. This technique is developed for electrically dispersive media (i.e., magnetically non-dispersive) and its generality allows the use of any kind of Debye and Lorentz models or media represented by a ratio of polynomials with full power of (j ω). The TLM-TW numerical scheme is first validated through the simulation of a canonical thin lead cable surrounded by a homogeneous Lorentz dispersive medium. Then, the numerical study of an umbrella antenna, radiating structure typically used in VLF transmissions, is investigated.

The European School of Antennas: Results and perspectives

The European School of Antennas (ESoA) is a new model of geographically-distributed school that has the objective to reinforce the European training and research in antennas and relevant applications. This paper presents the objective and perspectives of ESoA and the results obtained in 2006 and the first part of 2007 in terms of flow of students and teachers.

Coupled computational intelligence and time-domain method for design of the microwave devices

The coupled computational intelligence, in term of genetic algorithms and artificial neural networks, with the time-domain solver for design of the microwave devices is presented in this paper, where the coupled genetic algorithms with the time-domain solver is used for optimization and the artificial neural networks is used to surrogate the time-domain solver in design of the microwave components. This microstrip patch antenna and the microstrip meander line filter are used for evaluation of the performance of computational intelligence in design microwave devices.

Characterization of Printed Antennas with a Limited Ground Plane

A new numerical processing method is applied on the time-domain signal given by the Transmission Line Matrix method (TLM). It provides the possibility to characterize antennas such as stacked patches with a limited ground plane. We describe the techniques to obtain the radiation patterns, the input impedance and the wave polarization. The TLM simulates the propagation of electromagnetic waves in the time domain. Thus the characteristics can be obtained for a wide frequency band in a single TLM simulation. The effects of the limited ground plane are developped and shown on spatial representations of the electromagnetic fields. The results given by the TLM are compared with experimental ones.