Paul Delogne

EM propagation in tunnels

Various aspects of electromagnetic wave propagation in tunnels and of radio communication in such media are reviewed. A quantitative description is given for propagation in empty tunnels and in tunnels containing axial conductors or leaky feeders. The limitations of such simplified approaches are stressed. Quantitative studies of these phenomena are then reviewed. Engineering considerations are briefly mentioned. Attention is drawn to mode conversion techniques and to the multimode operation of systems. It is concluded that the theoretical aspects of EM wave propagation in tunnels are currently well understood, although work remains to be done on wideband and microwave communication systems. >

Deterministic modeling of the (shielded) outdoor power line channel based on the multiconductor transmission line equations

In this paper, a complete methodology is proposed for the deterministic modeling of the channel transfer functions associated with underground power line access networks, in the light of the Multiconductor Transmission Line Theory. Some multiconductor power line cables are analyzed in detail, and their fundamental propagation characteristics (definition of eigenmodes, phase velocity, characteristic impedance, lineic attenuation) are related to the geometry of the conductors and the material properties. A multidimensional scattering matrix formalism is then introduced to perform an accurate analysis of the global power line network including multiconductor cable segments, derivation points, and termination loads. An illustrative example of a power line access network with three types of cables (with different numbers of conductors), 20 derivations, and five remote terminals, is finally proposed.

Motion-compensated Conversion From Interlaced To Progressive Formats

This paper presents a new system for the conversion of interlaced formats to progressive ones. Like other proposals, it is motion compensation-based, but a substantial 2-fold improvement is added. First, assuming translational motions, the problem in the vertical direction is studied as a generalized interpolation problem. As a result, we derive two sets of linear filters which take into account the aliasing existing inside the fields. The first set of filters allows one to efficiently perform the interpolation which is required for subpel motion estimation. The second set of filters improves the estimation of the lines needed to obtain the progressive format, namely the deinterlacing process itself. Second, an improved block matching algorithm based on a split and merge procedure is used to estimate the motion and correctly propagate the motion vectors from blocks with reliable motion to blocks with uncertain motion. In order to tackle the problem of covered/uncovered objects, the whole process of estimation and motion-compensated interpolation is applied forward and backward. Simulation results and objective measurements are provided for artificially moving interlaced sequences obtained from a fixed picture and for a progressive sequence first converted to interlaced. The global system has also been tested on other sequences and visually assessed.

Theory of the Slotted Coaxial Cable

The electromagnetic problem of the coaxial cable with a continuous slot along the outer conductor is solved taking into account the dielectric constant of tbe cable insulation. Cylindrical harmonics expansions for the inner and outer space are used. The basic difficulty is to express boundary conditions on a part of the period in Fourier series. It appears that the singularity of the fields at the edge of the outer conductor plays a key role in the uniqueness of the result. The propagation constants of the monofilar and coaxial modes are obtained with a good accuracy. It is shown that these modes have different transfer inductances.

Underground use of a coaxial cable with leaky sections

The optimum efficiency of a leaky cable as a support for radio communications in tunnels involves a compromise between high leakage fields and a low increase of the coaxial mode attenuation. The latter is an important disadvantage of continuous leaky feeders. To obviate this, short leaky sections can be inserted in an otherwise well-shielded coaxial cable. These sections act as mode converters or radiators. A theoretical analysis based on coupled line theory enables us to determine the optimum characteristics of the leaky sections. Numerous experiments were carried out in a tunnel at various frequencies, using different lengths and characteristics of the leaky sections.

Block operations in digital signal processing with application to TV coding

Abstract Block operations make it possible to merge into one single multiplication many operations like filtering, downsampling, orthogonal transforms, etc. It is shown in the particular case of TV processing that the resulting effects of a block operation on small nonoverlapping blocks are very similar to the classical DSP operations based on convolutional and Fourier concepts. Step responses are presesented which illustrate these performances in the case of conversion of standard from 4 : 2 : 2 to 3 : 1 : 1. Simulations results have shown no visible impairment.

Universal Variable Length Coding for An Integrated Approach To Image-coding

We propose a new entropy coding scheme, denoted in this paper as the UVLC (universal variable length coding). It is universal in the sense that its efficiency is close to one for a large class of images. The UVLC, when it is applied to block orthogonal transforms, processes groups of blocks at the bit level, using universal codes designed for binary memoryless sources. It can be used for every video coding application, from high definition TV (HDTV) to high quality videotelephony (above 2 Mbit/s) for transform or subband coding. Last but not least, its implementation is very regular and can be realized in a single chip for the encoding oftv at theccir 601 format.RésuméLes auteurs proposent un nouveau schéma de codage entropique comme l’uvlc. Il est universel dans le sens où son efficacité est proche de un pour une large gamme d’images. L’uvlc, lorsqu’il est appliqué aux transformations orthogonales par blocs, traite des groupes de blocs au niveau du bit, en utilisant des codes universels développés pour les sources binaires sans mémoire. Ce schéma peut être appliqué pour toute application de codage vidéo, depuis latv à haute définition (TVHD) jusqu’à la vidéotéléphonie à haute qualité. Enfin, son implantation est très régulière et peut être réalisée en un seul circuit intégré pour l’encodage de signauxtv au formatccir 601.

Hierarchical encoding of HDTV by transform coefficients block splitting

This paper presents a solution for the hierarchical encoding of progressive HDTV sources, providing full downwards and upwards compatibility between HDTV, TV and High Quality Videophony (HQVT). As most of the video codecs at the present time are constituted with motioncompensated hybrid predictive4ransform structures, the solution is based on the splitting of transform coefficients blocks. A basic coding structure providing compatibility between two successive levels of the hierarchy is presented. A second point is devoted to the performance study of such a solution from the point of view of filtering and aliasing. This is done at the light of multirate filter banks theory.

Generalized interpolators for advanced movement-compensated 50 Hz-60 Hz conversion of interlaced sequences

Several television standards exist for TV and for HDTV signals. The worldwide interchange of programs makes the conversion between them of critical importance. Conventional transcoders use a static interpolation filter which is not able to deal with incorrectly bandlimited television signals. Motion compensation has been introduced in order to adapt interpolation to the signal. This approach proposes movement-oriented filtering and has been shown to give significant improvement. However, the known algorithms do not offer a perfect reconstruction step when the desired pixels have to be interpolated. A new system is proposed for the conversion between the popular interlaced TV standards (625 lines, 50 fields/s or 525 lines, 60 fields/s). The key feature is the use of generalized interpolators that are based on nonuniform sampling theory. The performance is compared with alternative interpolation techniques. In addition, the attached motion estimation algorithm relies on segmentation in the target field (i.e. the unknown 60 Hz field) to avoid assignment problems.

[Fine structure of microwave cross-polarization due to precipitation]

Microwave crosspolarization due to precipitation is generally attributed to the nonspherical shape of particles. In the simplest model [1] one assumes that the precipitation medium has two symmetry planes and only the coherent part of the field is taken into account. A canting of these planes must be assumed to explain the crosspolarization between vertical and horizontal polarizations. Theoretical investigations based on the equation of radiative transfer suggest a certain importance of non coherent scattering effects. This paper reports results of a threeyear experimental work and aims to give a better insight on the crosspolarization mechanisms.AnalyseLe changement de polarisation des hyperfréquences sous l’action des précipitations est généralement attribué à la forme non symétrique des particules. Dans le modèle le plus simple [1], on suppose que le milieu possède deux plans de symétrie et l’on ne tient compte que de la partie cohérente du champ. Il faut alors admettre une inclinaison de ces plans pour expliquer l’interférence entre les polarisations verticale et horizontale. Des recherches théoriques basées sur l’équation du transfert radiatif suggèrent cependant une certaine importance des effets de diffusion non cohérente. Cet article rapporte les résultats de trois années d’observation expérimentales et vise à donner une meilleure vue des mécanismes de changement de polarisation.