Investigation the influence of miniaturized RFID tag sensor on coupling effect

Purpose The skin and skeleton of aircraft are connected by adhesives or rivets to bear and transfer aerodynamic load. It is easy for crack and fracture damage to occur under the action of cyclic load, thus reducing aircraft bearing capacity/integrity and causing serious security risks. Therefore, it is particularly important that passive wireless radio frequency identification (RFID) sensors be used for the health monitoring of aircraft skin in its whole life cycle. This paper aims to investigate the influence of miniaturization on the coupling effect between RFID tag sensors. Design/methodology/approach Two groups of crack sensing systems based on RFID tags were designed. Gain and mutual impedance of sensor tags were analyzed via mode analysis. The reliability of crack detection of both sensing systems was compared using a preset experimental scheme. Findings Miniaturized antennas can reduce edge influence and the coupling effect. Gain and mutual impedance decrease with the increase in distance between dual tags. Backscatter power shows a decreasing trend and threshold power to activate tags in reader antenna increases. Results show that the miniaturization of size is more suitable for the application of multiple sensors. Originality/value By comparing two groups of sensing systems, the consistency of crack detection sensitivity is better when small tags are placed in parallel, which provides a theoretical basis for the application of small, passive and densely distributed crack sensors in the future.

Analysis of the Mutual Impedance of Coils Immersed in Water

Magnetic induction communication and wireless power transmission based on magnetic coupling have significant application prospects in underwater environments. Mutual impedance is a key parameter particularly required for the design of the systems. However, mutual impedance is usually extracted from measurements when the coils are processed, which is obviously not conducive to the system optimization in the design phase. In this paper, a model of the mutual impedance of coils immersed in water is established. The magnetic vector potential is expressed in the form of series by artificially setting a boundary, and then the mutual impedance calculation formula of the coils immersed in water is derived. In the analysis, the effect of the conductivity of water, the excitation frequency, and the number of turns of the coils are mainly taken into account. In addition, the variation of the mutual impedance of coils in air and water with axial displacement is also compared. The models can be used to analyze the coil coupling characteristics in the presence of conductive medium, which is helpful for the design process.

Mutual Coupling Compensation in Receiving Antenna Arrays

Mutual coupling compensation in uniform linear and circular receiving antenna arrays of thin wire dipoles is presented. It was observed that the mutual impedance is independent of the incident angle and depends solely on the geometry of the array. By using only one measurement, decoupling matrix is computed and direction of arrival is estimated.

Observations of a mix of cold and warm electrons by RPC-MIP at 67P/Churyumov-Gerasimenko

Context. The Mutual Impedance Probe (MIP) of the Rosetta Plasma Consortium (RPC) onboard the Rosetta orbiter which was in operation for more than two years, between August 2014 and September 2016 to monitor the electron density in the cometary ionosphere of 67P/Churyumov-Gerasimenko. Based on the resonance principle of the plasma eigenmodes, recent models of the mutual impedance experiment have shown that in a two-electron temperature plasma, such an instrument is able to separate the two isotropic electron populations and retrieve their properties. Aims. The goal of this paper is to identify and characterize regions of the cometary ionized environment filled with a mix of cold and warm electron populations, which was observed by Rosetta during the cometary operation phase. Methods. To reach this goal, this study identifies and investigates the in situ mutual impedance spectra dataset of the RPC-MIP instrument that contains the characteristics of a mix of cold and warm electrons, with a special focus on instrumental signatures typical of large cold-to-total electron density ratio (from 60 to 90%), that is, regions strongly dominated by the cold electron component. Results. We show from the observational signatures that the mix of cold and warm cometary electrons strongly depends on the cometary latitude. Indeed, in the southern hemisphere of 67P, where the neutral outgassing activity was higher than in northern hemisphere during post-perihelion, the cold electrons were more abundant, confirming the role of electron-neutral collisions in the cooling of cometary electrons. We also show that the cold electrons are mainly observed outside the nominal electron-neutral collision-dominated region (exobase), where electrons are expected to have cooled down. This which indicates that the cold electrons have been transported outward. Finally, RPC-MIP detected cold electrons far from the perihelion, where the neutral outgassing activity is lower, in regions where no electron exobase was expected to have formed. This suggests that the cometary neutrals provide a more frequent or efficient cooling of the electrons than expected for a radially expanding ionosphere.

Plasma characterization at comet 67P between 2 and 4 AU from the Sun with the RPC-MIP instrument

The plasma of comet 67P/Churyumov-Gerasimenko is analyzed based on the RPC-MIP mutual impedance probe data of the Rosetta mission. Numerical simulations of the RPC-MIP instrumental response considering two populations of electrons were fit on experimental responses acquired from January to September 2016 to extract the electron densities and temperatures. A time-tracking of the plasma parameters was performed, leading to the identification of a cold and a warm population of electrons during the period of interest. The respective densities and temperatures lie in the ranges [100; 1000] cm−3 and [0.05; 0.3] eV for the cold electrons and in the ranges [50; 500] cm−3 and [2; 10] eV for the warm electrons. Warm electrons most of the time made up between 10 and 30% of the whole population, while the temperature ratio between warm and cold electrons lay mostly between 30 and 70 during the period we studied. The fluctuation range of the plasma parameters, that is, the electron densities and temperatures, appears to have remained rather constant during the last nine months of the mission. We take the limitations of the instrument that are due to the experimental noise into account in our discussion of the results.

Analysis for Mutual Impedance of Pistons by Neural Network and Its Extension of Derivative

This study is basically a mathematical problem in sonar engineering. The sonar plays a very important role in underwater communication, detection, and remote sensing. Pistons are key sensors in a sonar system. The mutual coupling is a challenging problem in designing a sonar array. The mutual impedance of pistons is required in analyzing the mutual coupling of a sonar array. In this paper, a mathematical model consisting of a neural network and its extension of derivative is given and then utilized to analyze the mutual impedance of pistons. Initially, the mutual impedance of pistons is modelled and predicted by a neural network. By suitably extending the neural network, the derivative, i.e., slope information, for the neural-network output is obtained easily. Therefore, the mutual impedance and its slope information are obtained simultaneously almost in real time as the neural network is well trained in advance. Numerical examples show that the neural network can accurately predict the mutual impedance and its extension of derivative gives the slope information of mutual impedance simultaneously. It should be emphasized that the training work of a neural network is performed only once, i.e., only the training work in mapping the mutual impedance is required. No additional training work is required in obtaining the slope information.

Mutual Impedance Properties in a Lossy Array Antenna

The impedance matrix of an arbitrary multiport array antenna with Ohmic losses was studied. It was assumed that the partial current distributions in the array, corresponding to the alternate exciting one of its terminals while the other ones are open-circuited, are known. Consideration of the power balance in the lossy array antenna has allowed ascertaining that its impedance matrix is a sum of the radiation resistance matrix and loss resistance matrix, which are in general case complex Hermitian matrices and only in some particular cases can be real. The theoretical statements obtained are confirmed by two numerical examples, where analysis of two lossy dipole arrays was performed. In the first example, the dipoles were located above the imperfect ground, which served as a source of losses, and in the second example, the same dipoles were located in free space, and the embedded parasitic element was the source of losses. The results of the analysis showed that the asymmetric placement of energy absorbers in the array antennas leads to the appearance of imaginary parts in the matrices of radiation and loss resistances, which allow one to correctly predict the behavior of the array radiation efficiency during beam scanning.