Silver oxalate-based solders: New materials for high thermal conductivity microjoining

Micrometric oxalate powders can be decomposed starting from temperatures as low as 90°C, leading to the formation of temporary nanometric grains of metallic silver with a high propensity for sintering. The decomposition being highly exothermic, this additional energy favours the sintering, i.e. the soldering, process. Solders processed at 300°C and very low pressure (<0.5 MPa) displayed a thermal conductivity close to 100 W m-1 K-1, making silver oxalate very promising for safe, moderate temperature and very low pressure bonding

Deterministic channel modeling and performance simulation of microcellular wide-band communication systems

To evaluate the performance of future microcellular IMT-2000 modems, simple physical models are required, so that a number of system characteristics, such as the signal bandwidth, the antenna beamwidth, or the base station height can be accounted for at a limited computational cost. This paper describes a deterministic three-dimensional electromagnetic model, which allows simulation of the radiowave propagation for microcellular wide-band communication systems in urban areas. The model is based on a UTD ray-tracing tool and makes use of an improved mirror method. Simulated power-delay profiles are plotted against measured power-delay profiles recorded at 1.87 GHz in a street of Louvain-la-Neuve, Belgium, by means of an 80-MHz channel sounder. Despite several discrepancies, a satisfying matching is found considering three orders of reflection and single diffraction. Predictions of rms delay-spread accounting for the sounder limited bandwidth are presented. Finally, simulated and measured channels are also compared through the resulting performance of a typical IMT-2000 service in the presence of multiple access interference

A deterministic model for third generation mobile communication systems in urban environments

This paper describes a deterministic model which simulates the radiowave propagation for UMTS in urban areas. The model is based on a UTD ray-tracing tool, using the mirror method. Meanwhile, channel impulse responses (CIRs) have been measured in order to validate the ray-tracing tool. Measurements have been carried out at 1.87 GHz in a street of Louvain-la-Neuve (Belgium) by means of a wideband channel sounder. Simulated and experimental results are presented and compared quite satisfactorily in spite of several limitations.Anglai

Développement d'un filtre SIW multicouche en technologie LTCC High K en bande S

International audienceCet article présente le design et la mise en oeuvre d'un filtre SIW en bande S, d'ordre 12, utilisant la technologie High K LTCC. Il s'agit de proposer un filtre 3D miniature sur la base de cavités SIW réalisés à partir de couches LTCC à haute permittivité. On souhaite ici profiter de la forte constante diélectrique et de la possibilité d'empiler les cavités pour limiter l'empreinte de la structure. On souhaite aussi travailler sur des cavités volumiques pour atteindre de bons facteurs de qualité. La solution proposée permet de répondre à un gabarit de filtrage exigeant pour une application spatiale, qui présente une forte rejection hors bande et un niveau faible de pertes d'insertion et d'ondulation dans la bande passante

Compact SIW Filter in High-K LTCC Technology for a Space Application

International audienceSubstrate Integrated Waveguide (SIW) enhances the Q-factor compared with classical planar techniques. Its integration capabilities and fabrication costs are among the assets that make it attractive. The counterpart is their size that is higher than their planar equivalents. This paper proposes an association of two solutions to reduce SIW size while keeping good electrical performances: the use of LTCC technology and high permittivity substrate. The aim is to demonstrate the possibility to build a compact, high performance X-band filter on a ceramic substrate through a multi-layer approach. This paper reports on the design of a 6th-order filter with drastic specifications for space application

Ultra-compact X-band SIW filter in LTCC technology using high permittivity substrate for a space application

International audienceSubstrate Integrated Waveguide (SIW) provides a better Q-factor compared with the other planar techniques. Its integration capabilities and fabrication cost are other benefits that make it attractive. But SIW filters are bulkier than their equivalents achieved in microstrip technology. This paper reports on the association of two solutions to reduce size and make SIW even more attractive: LTCC technology to stack cavities and high permittivity substrate. The objective is to demonstrate the possibility to build high performance X-band filter on a ceramics through a multi-layer approach. The solution is tested on a X band-dedicated 6th-order filter with drastic specifications for space application

Presentation of different technologies of X-band filters for frequency converters application

International audienceThis paper proposes a presentation of three technologies of filters, integrated in microwave frequency converters, for space application in X band. These new developments are realized in order to improve the filter performances and/ or to reduce their size. The three solutions are developed in this paper. Simulation and measurement results are presented