Potassium-and silver-double-ion-exchanged slab glass waveguides: characterization and modeling

International audienceDouble-ion-exchanged glass waveguides are made first by a potassium-ion exchange followed by a silver-ion exchange. The inverse WKB method is used to determine the index profile. It is shown that a combination of a truncated quadratic function and a complementary error function represents the refractive index best. A direct WKB method is employed to find the maximum index change and the diffusion coefficient of the second exchange process. The concentration of silver, potassium, and sodium ions are measured by an x-ray photoelectron spectroscopy technique. The results agree well with the index profile when a quadratic function is used

New method to design directional coupler dual wavelength multi/demultiplexer with bends at both extremities

International audienceA new method to easily and accurately design a dual wavelength multi/demultiplexer is developed. It takes into account the bend sections at both extremities that are needed to have a realistic separation between the input and the output ports. A 1.30/ 1.55 Ixm multi/demultiplexer made by double ion-exchange in BK7 glass is studied to illustrate the proposed method. Refractive index of channel waveguides is obtained by solving the diffusion equation using the finite difference Dufort-Frankel method. WKB formula is then used to transform the index distribution into a one-dimensional array. The parameters needed to determine the optimum length and axial separation of the parallel waveguides are evaluated by a two dimensional BPM simulation for TM polarization. Better than-25 dB crosstalk are obtained. A study of the sensitivity of the couplers relative to the ion exchange time is carried out

Miniature 3D Wire Antenna for RFID UHF Reader Using Genetic Algorithm

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Circular antenna array for microwave Bessel beam generation

International audienceA circular antenna array (CAA) is proposed and demonstrated for the generation of optimal pseudo-Bessel beams at millimeter-wave frequencies. Numerical simulations show that a 91-element array produces a Bessel beam of a 7λ main lobe width over a distance of 180λ. Based on this report, it is suggested that Bessel beams may provide a unique solution to millimeter-wave quasi-optical systems by providing highly focused beams with small-sized antennas

Etude de nouvelles fonctions radiofréquences à base d'antennes à onde de fuite composite main droite/gauche

Dans ce travail, nous nous intéressons au développement de nouvelles fonctions radiofréquences basée sur des Antennes à Onde de Fuite (AOF) de type composite main gauche/droite (CRLH en anglais). La première partie de la thèse concerne la modélisation circuit et la conception automatique d AOF CRLH. Nous avons prouvé que le modèle classique décrivant des capacités interdigitées devait être complété, ce que nous avons fait. Nous avons aussi développé un outil semi-automatique d aide à la conception d une cellule CRLH en technologie microruban. Ensuite, nous avons développé une méthode entièrement automatique de conception de lignes CRLH que nous avons appliquée à la conception d une AOF CRLH non uniforme afin de minimiser les lobes secondaires. La troisième partie porte sur la conception d une AOF électronique permettant un balayage spatial à fréquence fixe tout en conservant l adaptation. La quatrième partie est dévouée à l utilisation des AOF CRLH dans un réseau circulaire plan pour des applications de focalisation.This work deals with the study of new radiofrequency applications based on the Composite Right/Left Handed (CRLH) Leaky-Wave Antenna (LWA). In the first part, we introduce the LWA and the CRLH theory. In the second part, circuit modelisation and automate design of CRLH strucutures are presented. We proved that the classical circuit model of interdigital capacitors needed to be completed and improved. We also developed a semi-automated tool for the synthesis and the analysis of a micro-strip CRLH unit cell. Afterword, a first fully automated approach to design CRLH transmission lines is presented. We used this approach to reduce the side lobes level of a non uniform CRLH LWA. The third part is devoted to the design of an electronic CRLH LWA using a double tuning to scan at constant frequency without mismatching. The subject of the fourth part is the use of phased antenna array for focalisation applications. Finally, a novel use of CRLH LWA in a phased antenna array is presented.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Compact wideband multi-arm 3-D wire antenna for GNSS applications

In this paper, a novel multi-arm crooked wire antenna designed with a multi-objective genetic algorithm (MOGA) is presented. The proposed topology offers a small size, lightweight, and a wideband −10 dB impedance matching. Its fully metallic nature preserves a high radiation efficiency. The multi-arm topology is discussed, and the impact of the number of arms and segments is studied. A proof of concept is optimized, fabricated, and tested. It occupies a volume less than 0.11 λ × 0.13 λ × 0.14 λ, where λ is the wavelength at the lowest operating frequency and covers the entire Global Navigation Satellite System services frequencies with a bandwidth of 503.5 MHz which represents 35.56%, without any matching network. The antenna’s fully metallic structure results in a radiation efficiency higher than 98% and a gain of 8.66 dBi. Measurement results agree with simulations and are elaborated around the frequencies of the lower (1164–1300 MHz) and upper (1559–1610 MHz) bands of the L-band spectrum. A realization-friendly fabrication technique is proposed to realize the 3-D multi-arm wire antennas with high accuracy. The rigid fully metallic structure makes the antenna very suitable to operate in harsh environments, as in aerospace and military applications where substrate-based antennas are unqualified

Generation of Bessel Beams by Two-Dimensional Antenna Arrays Using Sub-Sampled Distributions

International audienceBessel beams are proposed as a practical way to generate well collimated and confined beams at mm-waves or THz for quasi-optical applications. To achieve that, we propose the use of two-dimensional antenna arrays as realizable launchers. Truncated Bessel beams with a main lobe width of few wavelengths (l) can propagate over several hundreds of l if the antenna aperture is electrically large. Because such a large aperture would require a large number of antenna elements, subsampling distributions are proposed in this work. It is found that arrays with spacings of approximately 4l generate high quality beams with very low amplitude oscillations over distances of about 300l in vacuum. The optimal excitation function for such arrays greatly departs from the Bessel one. It is synthesized with an analytical method based on a least mean square error minimization. The synthesis method is scalar, but the pseudo- Bessel beams obtained are vectorial and linearly polarized. Theoretical predictions are confirmed by full-wave simulations using Ansoft Designer

Antenne filaire tridimensionnelle très compacte pour applications RFID UH

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A new solution to waveguide excitation suppressing the effects of the radiated field. Application to the Y-junction

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Antenne filaire tridimensionnelle très compacte pour applications RFID UH

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