This paper demonstrates how micro-cracks at the surface of metals can be detected and imaged by near-field microwave techniques from the crack-induced variations of the resonance frequency and of the resonant circuit quality factor. It deals with two resonant sensors: a quarter wavelength microstrip line resonator terminated by an electric dipole and an original dual-behavior resonator (DBR) band-pass filter probe. The detection principle is developed, at first, from the use of the electric dipole probe. The low sensitivity of the electric dipole resonator led us to investigate whether first-order band-pass filters based on dual behavior resonators were able to detect a 200 µm wide and 3 mm deep rectangular EDM notch at the surface of a steel plate used to validate our method. Simulation data and measurements results carried out on a stainless steel mock-up with several 200 µm wide EDM rectangular notches showed that the DBR sensor is more sensitive than the electric dipole probe, and highlighted the link between the spatial resolution and the width of the high-frequency stub of the DBR filter. Moreover, we demonstrate the notch detection for any orientation of the defect in relation to the DBR sensor and the ability to differentiate between notches of different depths. Simulation data and measurement results are presented and discussed.

Recent studies proved that certain electronic active circuits are capable to exhibit simultaneously a negative group delay (NGD) and amplification in microwave frequency bands. One of the simplest topologies generating this counterintuitive NGD function effect is formed by a series RLC-network in cascade with a transistor. By using this cell, similar to the classical electronic functions, dual-band NGD microwave devices with loss compensation possibility can be designed. Theoretic demonstrations concerning the theory of the NGD circuit considered are presented. The dual-band NGD concept feasibility is concretely illustrated by an example of EM/circuit co-simulations. So, in frequency domain, dual-band NGD with minimal values of about-1 ns was observed simultaneously within two frequency bands centered at about 1.05 GHz and 2.05 GHz. To highlight the functioning of the hybrid device considered, time-domain analysis showing the RF/microwave signal advancement is performed. As application, the concept investigated can be envisaged for data synchronization in multi-channel wireless communication systems eventually degraded by undesired EMI effects.

International audienceA power-over-fiber system using a single fiber optic of 10km devoted to transmit the energy to supply a remote equipment and also the up/down-stream data exchanged between a shore station and the equipment, is presented in this paper. Firstly, we present an overview of the developed quasi-all-optical architecture and its main communication protocol: the SPI. Then, we focus on its low consumption remote equipment and more precisely on a device called “the interface instrument” which is made of two main units. One realizes the optical toelectrical conversion to provide the power supply. The other one manages the optical data. Afterwards, experimental characterizations of the prototype are given and discussed

The variation in the permeability of a multilayered polyvinylidene fluoride/CoFeB (piezoelectric/magnetostrictive) composite material under the action of a dc voltage is demonstrated. The driven-voltage permeability is first predicted using a finite element method-based multiphysics calculation. The simulation allows us to determine a magnetic anisotropy field of 45 Oe induced in the ferromagnetic layers by the mechanical coupling between magnetostrictive and piezoelectric layers due to the applied dc voltage. A variation of 30% for the permeability of the ferromagnetic layers is then measured using a radiofrequency permeameter and under the application of a dc voltage of 15 V applied on the ferromagnetic layers, which also act as electrodes for the bias of the polyvinylidene fluoride (PVDF). An additional measurement of the trilayered structure under the application of a dc magnetic field is finally performed to evaluate the magnetic field needed to get a 30% variation in the magnetic layers permeability in order to compare this value to the one predicted by multiphysics calculation. These experimental results are in good agreement with calculations and are very encouraging for the application of the CoFeB/PVDF/CoFeB composite material to ensure the tunability of microwave devices (filters, phase shifters, antennas, etc.)