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There is a growing pressure on antenna designers to provide ever increasing operating bandwidth, efficiency, and flexibility. Emerging communications standards are requiring operation over wide frequency ranges, often with multiple, separated bands of operation. This communication proposes and demonstrates an optically tunable cavity backed slot antenna. Through the incorporation of four silicon bridging pieces and a fiber coupled laser, the operating frequency can be tuned between 4.2 and 6 GHz. Antenna efficiency has been measured and ranges between 36% and 62% depending upon the combination of frequency and tuning state, with the gain taking values between 4.3 and 6.9 dBi. An effective fabrication process for the incorporation of silicon into the antenna has been described, as well as methods for effectively simulating the optically generated conductivity. Simulations and measurements show good agreement, and several proposed improvements are proposed for this novel and flexible tuning technology.

We provide an approach to reformulate the problem of extracting the information on scatterers in inverse problems. The approach is based on the recently introduced concept of singular value optimization and exploits the single scattering hypothesis of the Born approximation. A two-dimensional geometry with multifrequency/single-view plane wave illumination and TM polarization with near-field acquisitions is considered. Numerical results show how it is possible to dramatically reduce the number of near-field samples against the canonical ${{\rm{\lambda }}_{{\rm{min}}}}{\rm{/2}}$ criterion.

Local electromechanical (EM) measurements were performed in Pr doped BiFeO3 (BPFO) ceramics via piezoresponse force microscopy (PFM). The results revealed that local EM response was different from the macroscopic one due to the large contribution of the leakage current. The locally measured response was used to evaluate effective piezoelectric coefficient d33 of the material. The multi-frequency PFM mode with additional compensation of the cantilever-surface Coulomb interaction under application of the external DC bias provided the most accurate values of the effective d33 coefficient and allowed studying its surface distribution and residual depolarization field distribution across the surface of BPFO ceramics. © 2018 Taylor & Francis Group, LLC.

Overhauser-DNP-enhanced homonuclear 2D 19F correlation spectroscopy with diagonal suppression is presented for small molecules in the solution state at moderate fields. Multi-frequency, multi-radical studies demonstrate that these relatively low-field experiments may be operated with sensitivity rivalling that of standard 200-1000MHz NMR spectroscopy. Structural information is accessible without a sensitivity penalty, and diagonal suppressed 2D NMR correlations emerge despite the general lack of multiplet resolution in the 1D ODNP spectra. This powerful general approach avoids the rather stiff excitation, detection, and other special requirements of high-field 19FNMR spectroscopy. � 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In this paper we describe a method to monitor for a difference in the ionospheric delay observed by a ground station of a Ground Based Augmentation System (GBAS) and an airborne user. In case of detection the affected satellite can be excluded or a switch to an ionospheric free processing mode can be triggered. As it is not possible to estimate the absolute ionospheric delay at the ground station from the transmitted corrections directly, we compare a pseudo-ionospheric delay estimate from the corrections with an ionospheric estimate after removing biases. We then show the performance of the proposed monitoring architecture in flight trials from our GBAS test environment for different scenarios. In order to obtain results for a full constellation we considered an L1/L2 dual frequency combination where the expected noise and multipath is larger than in the L1/L5 case which will be used in an operational GBAS. Results show that even with the larger test statistic and in the single constellation case the monitor is feasible and provides good results. Furthermore, we also show results using the available L5/E5a signals collected during flight tests. Also in this case the performance is good and the threshold was not exceeded despite the low threshold of the monitor due to the marginal geometry. In order to test the reaction of the monitor to ionospheric gradients we injected a simulated error into the airborne measurements. As the monitoring threshold depends on the satellite geometry we show some exemplary results of the impact of different gradient slopes on the test statistic of the affected satellites.

International audience; In a recent communication, we presented a compact multi-frequency meander antenna [1]. This structure has a potential to be reconfigurable by using varactor diode. We plan to present this study in a future conference. In this paper, we present a mechanically tunable meander antenna by adjusting a floating ground plane placed under the meander structure. the use of mechanical tunable technique is very interesting because it provides a very simple handling of the power, no risk of nonlinearity and a continuous tunable capability. We present in this paper two possibilities of tunable device, one with the displacement of the floating ground plane and the second with the use of moving copper wires. Simulated and measured results are presented and discussed. © 2016 European Association of Antennas and Propagation.

Material parameter characteristics of a photonic multi-band-gap structure, relying on strip-line technology, is presented. Two layers of dielectric fill the space between two metallic planes and surround a periodic 2D lattice of rectangular metallic patches connected to the ground plane through metallic vias. The variations of the dispersion diagrams with the dielectric constant of one of the layers as parameters are calculated by electromagnetic simulation. Due to the large number of band-gaps the structure presents in the microwave range, it may find applications in multifrequency filter design and enhanced sensibility sensor construction.

The mutual coupling between elements of a multifrequency dipole antenna array is experimentally investigated by S-parameter measurements and planar near-field scanning of the radiated field. A multifrequency array with six dipoles is analyzed. In order to reduce the coupling between dipoles, a planar metasurface is placed atop the array acting as superstrate. The mutual coupling of the antenna elements in the absence and presence of the superstrate is presented comparatively. Between 3 and 20 dB mutual coupling reduction is achieved when the superstrate is used. By scanning the field radiated by the antennas and far-field measurements of the radiation pattern, it is observed that the superstrate confines the radiated power, increases the boresight radiation, and reduces the endfire radiation., European Council; Spanish Government; Scientific and Technological Research Council of Turkey (TÜBİTAK)

Cataloged from PDF version of article. Strong reduction of the scattering cross section is obtained for subwavelength dielectric and conducting cylinders without any magnetism for both TE and TM polarizations. The suggested approach is based on the use of Fabry-Perot type radial resonances, which can appear in single-layer, high-ε, isotropic, and homogeneous shells with the properly chosen parameters. Frequencies of the minima of the scattering cross section, which are associated with the cloaking, typically depend on whether TE or TM polarization is considered. In some cases, large-positive-ε and largenegative-e objects can be cloaked. In other cases, non-ideal multifrequency cloaking can be realized. ©2009 Optical Society of America.

Part VI: Haptics Applications; International audience; This paper presents a real-time physically based platform for multi-sensory interactive simulation. It is centred on high quality dynamic requirements driven by the concept of instrumental interaction and is able to render a wide variety of physical phenomena : from very rigid interactions to large and complex phenomena such pastes or plastic soils. The platform consists in a precisely synchronized multiprocessor architecture extended with a DSP board used for the simulation of very reactive models. It aims for obtain simulation rate necessary for rigid object (1KHz and more) in the context of 6 Degree of Freedom.