On-chip circularly polarized circular loop antennas utilizing 4H-SiC and GaAs substrates in the Q/V band

This paper presents a comprehensive assessment of the performance of on-chip circularly polarized (CP) circular loop antennas that have been designed and fabricated to operate in the Q/V frequency band. The proposed antenna design incorporates two concentric loops, with the outer loop as the active element and the inner loop enhancing the CP bandwidth. The study utilizes gallium arsenide (GaAs) and silicon carbide (4H-SiC) semiconductor wafer substrates. The measured results highlight the successful achievement of impedance matching at 40 GHz and 44 GHz for the 4H-SiC and GaAs substrates, respectively. Furthermore, both cases yield an axial ratio (AR) of less than 3 dB, with variations in bandwidths and frequency bands contingent upon the dielectric constant of the respective substrate material. Moreover, the outcomes confirm that utilizing 4H-SiC substrates results in a significantly higher radiation efficiency of 95%, owing to lower substrate losses. In pursuit of these findings, a 4-element circularly polarized loop array antenna has been fabricated for operation at 40 GHz, employing a 4H-SiC wafer as a low-loss substrate. The results underscore the antenna’s remarkable performance, exemplified by a broadside gain of approximately 9.7 dBic and a total efficiency of circa 92%. A close agreement has been achieved between simulated and measured results

Simulation sous Matlab/Simulink d'une chaîne de transmission numérique en bande de base. Application au codage canal

Cet article présente une expérience d'enseignement des techniques de codage de canal [1-8] à l'Université de Bretagne Occidentale à Brest. Cet enseignement, développé sous le logiciel Simulink, s'adresse à des étudiants de second cycle en électronique et télécommunications. Il repose sur la mise en oeuvre de codeurs/décodeurs de canal classiques au sein d'une chaîne de transmission numérique. La transmission se fait en bande de base, sur un canal idéal perturbé par du bruit. Une telle manipulation permet aux étudiants de visualiser aisément l'efficacité des techniques de codage sur la sécurisation de l'information transmise, mais aussi en contrepartie la dégradation du débit

Résonateur reconfigurable à base de lignes couplées à éléments d'accord intégrés sur substrat silicium

International audienceThis paper presents a particular technique of reconfiguration of coupled line resonators. The reconfigurability is obtained by doping one or more parts of the silicon substrate located at the level of the coupled lines, thus creating one or more distributed diodes. The entire circuit goes through a co-design offering great flexibility and a considerable reduction in losses linked to the interconnection between the passive and active element. A first two-state resonator is presented, it has a resonance frequency close to 2.5 GHz in the OFF state and a frequency of 1.5 GHz in the ON state; the latter being adjustable as a function of the position of the doped zone. A second three-state resonator is also presented, its resonant frequency switches from 2.5 GHz in the OFF state, to 1.62 GHz in the ON1 state then to 2.13 GHz in the ON2 state.-Ce papier présente une technique particulière de reconfiguration de résonateurs à lignes couplées. La reconfigurabilité est obtenue par le dopage d'une ou plusieurs parties du substrat silicium situées au niveau des lignes couplées, créant ainsi une ou plusieurs diodes distribuées. L'intégralité du circuit passe par une coconception offrant une grande flexibilité et une réduction considérable des pertes liées à l'interconnexion entre l'élément passif et actif. Un premier résonateur deux états est présenté, il possède une fréquence de résonance proche de 2,5 GHz à l'état OFF et une fréquence de 1,5GHz à l'état ON ; cette dernière étant ajustable en fonction de la position de la zone dopée. Un deuxième résonateur trois états est également présenté, sa fréquence de résonance commute de 2,5 GHz à l'état OFF, à 1,62 GHz à l'état ON1 puis à 2,13 GHz à l'état ON2

Implementation of ground plane membranes to realize a bandwidth and frequency tunable filter

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Fully integrated microsystem using microfluidic devices to tune or reconfigure RF circuits

International audienceThis paper presents preliminary de-vices and results of tunable microwave microsystem associating RF circuits and microfluidic components. Dielectric fluids are used to disrupt the permittivity of a microstrip structure and thus change its operating frequency. In this approach, stop-band metallic stubs are placed on top of SU8 structured substrate. Without changing the shape of RF function, its frequency shift is more than 20% when deionized water is flowing in fluidic channels

Fully integrated microsystem using microfluidic devices to tune or reconfigure RF circuits

International audienceThis paper presents preliminary de-vices and results of tunable microwave microsystem associating RF circuits and microfluidic components. Dielectric fluids are used to disrupt the permittivity of a microstrip structure and thus change its operating frequency. In this approach, stop-band metallic stubs are placed on top of SU8 structured substrate. Without changing the shape of RF function, its frequency shift is more than 20% when deionized water is flowing in fluidic channels

Fully integrated microsystem using microfluidic devices to tune or reconfigure RF circuits

International audienceThis paper presents preliminary de-vices and results of tunable microwave microsystem associating RF circuits and microfluidic components. Dielectric fluids are used to disrupt the permittivity of a microstrip structure and thus change its operating frequency. In this approach, stop-band metallic stubs are placed on top of SU8 structured substrate. Without changing the shape of RF function, its frequency shift is more than 20% when deionized water is flowing in fluidic channels

Handling separable non-convexities using disjunctive cuts

International audienceD'Ambrosio, Lee, and Wächter (2009, 2012) introduced an algorithmic approach for handling separable non-convexities in the context of global optimization. That algorithmic framework calculates lower bounds (on the optimal min objective value) by solving a sequence of convex MINLPs. We propose a method for addressing the same setting, but employing disjunctive cuts (generated via LP), and solving instead a sequence of convex NLPs. We present computational results which demonstrate the viability of our approach