Romain Pascaud

Exposure Assessment Using the Dual-Grid Finite-Difference Time-Domain Method

A new way to carry out numerical cellular telephone simulation in the presence of the head is presented. Here, two finite-difference time-domain (FDTD) simulations with different spatial and time resolutions are sequentially combined to perform a dual-grid FDTD (DG-FDTD) simulation. The DG-FDTD approach has the significant advantages to remain stable along the computation and to be easy to implement in a typical FDTD code. When compared with classical FDTD analysis, the DG-FDTD approach exhibits a reduction in computation time and memory requirements by a factor of 2.3 and 3.2, respectively, while providing accurate results both in near-field and far-field radiation.

New DG-FDTD method: Application to the study of a MIMO array

In this paper, we propose a new rigorous multiresolution approach for FDTD simulation that reduces the computational time, and prevents from instabilities. First, we present the studied MIMO array. Then, the principle of the DG-FDTD is exposed in connection with the array design. Finally, we evaluate the accuracy and the performance of the DG-FDTD method while characterizing the performance of the studied array.

Compact dual-polarized VHF microstrip antenna for satellite applications

This paper presents the design of a compact dual-polarized VHF microstrip antenna for modern small satellites. It consists of a slot-loaded annular-ring microstrip antenna printed on a light substrate to reduce its mass. A simple matching circuit is proposed to match the high input impedance of this antenna while enabling the generation of a dual linear-polarization. The size of the proposed design is finally equal to 450 mm at 161 MHz, i.e. λ0=4.

Comparison of SAGE and classical multi-antenna algorithms for multipath mitigation in real-world environment

The performance of the Space Alternating Generalized Expectation Maximisation (SAGE) algorithm for multipath mitigation is assessed in this paper. Numerical simulations have already proven the potential of SAGE in navigation context, but practical aspects of the implementation of such a technique in a GNSS receiver are the topic for further investigation. In this paper, we will present the first results of SAGE implementation in a real world environment.

Integration of a multi-sector antenna system on a wireless camera

The issue of the integration of a multi-sector antenna system onto a wireless camera has been addressed from simulation and application point of view. The obtained results show that the effect of the camera on the multi-sector antenna system could not be neglected and should be taken into account at the early phase of the antenna design. Simulations and measurements have shown the interest of using a multi-resolution method such as the DG-FDTD method in the simulation of antenna system including its close environment. One potential solution to limit the disturbance of the antenna performances by the camera handling may rely on the tilt of the concerned beams by using metallic directors properly positioned into the antenna radome [4].

A New Multiresolution FDTD Approach Based on the Hybridization of MR-FDTD and DG-FDTD Methods

In this paper, a new multiresolution approach based on the hybridization of the well-known multiple-region FDTD (MR-FDTD) and the new dual-grid FDTD (DG-FDTD) is applied to simulate the transmission between two ultra wide-band (UWB) antennas. The good results for the S parameters as well as the large gain on computational time makes the hybrid MR-FDTD / DG-FDTD method a good simulation approach for large problems.

Static and dynamic control of limiting threshold in plasma-based microstrip microwave power limiter

Static and dynamic control of the limiting threshold in a very low-loss plasma-based microstrip power limiter is investigated in order to prevent receivers from being threatened by high-power microwave (HPM). An analytic model of the microstrip circuit is proposed to derive the influence of its design on the limiting threshold of the microwave power limiter. Experimental results are in good agreement with those expected. Finally, an original approach to allow discrete limiting threshold tunability is presented and validated experimentally.

Modeling and experimental measurements of a tunable microstrip resonator using plasma discharges

In this paper, we suggest the use of a cold plasma as tunable material inside a microstrip resonant cavity. Plasma dielectric constant can indeed be moved to values below 1 to tune its resonant frequency. DC plasma analysis were conducted and integrated into classic electromagnetic solvers to investigate tuning abilities. Numerical simulations are consistent with experimental results and make this original tuning techniques viable for high power applications.

Antena impresa invertida reconfigurable en frecuencia a base de una microdescarga de plasma

espanolEn este articulo se propone el estudio de una antena impresa invertida reconfigurable en frecuencia a base de una microdescarga de plasma. La idea es generar una microdescarga controlada en corriente al interior de una cavidad situada entre el plano tierra de la antena y su conductor principal, cuyo objetivo final es de modificar la frecuencia de resonancia de la antena. El interes en la utilizacion del plasma como elemento reconfigurable es su tiempo de conmutacion y, sobre todo, su capacidad de manejo de altas potencias. Se demostro de manera teorica que la reconfiguracion en frecuencia de una antena tipo parche, con una microdescarga en su cavidad, es dependiente de la densidad electronica del plasma. Ademas, se implemento un prototipo de antena impresa invertida reconfigurable en banda X integrando una microdescarga, la que tuvo excursion en frecuencia medida de 180 MHz. EnglishThis paper proposes the study of an inverted microstrip plasma-based reconfigurable antenna. The scope is to generate controlled microplasma inside the cavity between the antenna ground plane and its main conductor. This plasma will modify the resonant frequency of the antenna. The interest of using a plasma discharge as an active reconfigurable element is its switching time and mainly its capability of handling high microwave power. It was demonstrated, theoretically, that the reconfiguration frequency of a microstrip patch antenna with a microdischarge in its cavity, depends on the electron density of the plasma. Furthermore, a prototype of an X-Band inverted microstrip patch antenna, which integrates a microdischarge, was implemented. The measured frequency excursion for this prototype was 180 MHz

Multiresolution fdtd with switchable grid

A new multiresolution approach for the FDTD is proposed and applied to an ultra wide-band (UWB) problem. The multiresolution FDTD with switchable grid (SWG-FDTD) splits the simulation along the time into two FDTD schemes with different mesh densities. The fist part of the simulation is carried out using fine mesh in order to take into account the strong near-field variations. The second part of the SWG-FDTD simulation uses a coarse mesh to finish the simulation. In our example, it enables a 60 % gain in computation time while maintaining good accuracy on the results.