MIMO Capacity Estimation at 2 GHz with a Ray Model in Urban Cellular Environment

MIMO technology promises a linear increase of capacity in function of the minimum antenna number at the transmitter and at the receiver. In order to test if these performances can be actually met in mobile communications, we propose here a study of MIMO (Multiple Input Multiple Output) capacity in urban cellular environment at 2 GHz with a help of an efficient ray propagation model. We have tested different types of base station antennas (vertically or ±45° polarized) and two different types of mobile. Capacity is found to significantly increase between SISO (Single Input Single Output) and MIMO systems, but less than usually expected. We show that return and coupling losses as low as 10% can also reduce significantly the capacity. On the other hand, we study the influence of the way to take into account received power level on the MIMO capacity estimation

Dynamic effective anisotropy: Asymptotics, simulations, and microwave experiments with dielectric fibers

International audienceWe investigate dynamic effective anisotropy in photonic crystals (PCs) through a combination of an effective medium theory, which is a high-frequency homogenization (HFH) method explicitly developed to operate for short waves, as well as through numerical simulations and microwave experiments. The HFH yields accurate predictions of the effective anisotropic properties of periodic structures when the wavelength is of comparable order to the pitch of the array; specifically, we investigate a square array of pitch 2 cm consisting of dielectric rods of radius 0.5 cm and refractive index n=6√ within an air matrix. This behaves as an effective medium, with strong artificial anisotropy, at a frequency corresponding to a flat band emerging from a Dirac-like point in transverse magnetic (TM) polarization. At this frequency, highly directive emission is predicted for an electric source placed inside this PC, and this artificial anisotropy can be shown to coincide with a change of character of the underlying effective equation from isotropic to unidirective, with coefficients of markedly different magnitudes appearing in the effective equation tensor. In transverse electric (TE) polarization, we note a second radical change of character of the underlying effective equation, this time from elliptic to hyperbolic, near a frequency at which a saddle point occurs in the corresponding dispersion curves. Delicate microwave experiments are performed in both polarizations for such a PC consisting of 80 rods, and we demonstrate that a directive emission in the form of a + (respectively, an X) is indeed seen experimentally at the predicted frequency 9.5 GHz in TM polarization (respectively, 5.9 GHz in TE polarization). These are clearly dynamic effects since in the quasistatic regime the PC just behaves as an isotropic medium

A porosity gradient in 67P/C-G nucleus suggested from CONSERT and SESAME-PP results: an interpretation based on new laboratory permittivity measurements of porous icy analogues

The Rosetta spacecraft made a rendezvous with comet 67P/Churyumov-Gerasimenko (67P) in 2014 August, soon after the Philae module landed on the small lobe of the nucleus on 2014 November 12. The CONSERT instrument, onboard Rosetta and Philae, sounded the upper part of the interior of 67P with radiowaves at 90 MHz and determined an average of the real part of the permittivity (hereafter ) equal to about 1.27. The SESAME-PP instrument, onboard Philae, sounded the near-surface of the small lobe in the 400–800 Hz range and determined a lower limit of equal to 2.45. We use a semi-empirical formula obtained from measurements of performed in the laboratory at 243 K on water ice and ice-basaltic dust mixtures, with a controlled porosity in the 31–91 per cent range and a dust-to-ice volumetric ratio in the 0.1– 2.8 range, to interpret the results of the two instruments, taking into account the temperature and frequency dependences. A graphical method is proposed to derive ranges of porosity and dust-mass fraction from a value of derived from observations. The non-dispersive behaviour of below 175 K, allows us to compare the values of obtained by CONSERT and SESAME-PP. We show that the porosity of the small lobe of 67P increases with depth. Based on new measurements of analogues of complex extraterrestrial organic matter, the so-called tholins, we also suggest that, for the dust component in the cometary material, the presence of silicates has more effect on than organic materials

Real-time microwave sensor system for detection of polluting substances in pure water

International audienc

Electromagnetic characterization of grouting materials of bridge post tensioned ducts for NDT using capacitive probe

The use of a capacitive probe as a non-destructive investigative technique for controlling the post tensioned ducts of bridges has gained increasing acceptance in France since several years. A field campaign measurement made in 2006 has shown the performance of the capacitive probe developed by the IFSTTAR. Nevertheless, some results are not understood, and in particular the behaviour of the probe when cement exudation product are present in the duct. Without an accurate knowledge of the electromagnetic properties of those products it is impossible to quantitatively assess the results of our capacitive probe. This paper reports the development of a coaxial transmission line feature. It was designed to allow the evaluation of a large type of material (liquid, paste or granular) over a large frequency range (50 MHz-4 GHz at maximum). A calibration scheme developed before at the Fresnel Institute was used. Using a two port S parameter instrument, the complex permittivity and magnetic permeability were evaluated by frequency domain measurement. The electromagnetic characterization of cement paste, cement exudation products and injection wax has brought us some key results in the interpretation of the capacitive probe signal. The results of this characterization were then used in a 3D semi analytical modelling of the problem. The studies of configurations with exudation products are presented and compared to experimental results obtained with our capacitive probe on laboratory duct