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Multiple-Input Multiple-Output (MIMO) is one of the key technology components in the fifth generation communication (5G). Inevitably, the growing antenna number in a limited space makes mutual coupling (MC) effect severely influence the system performance of wireless communication. Therefore, accurate MC modeling is of great significance to eliminate MC effects. To this end, we propose a new MC modeling approach based on deep learning to model MC effect in massive MIMO system. For the sake of realizing the processing of complex data with deep neural network (DNN), we divide the complex data into real and imaginary parts, and deduce the expression of mean square error (MSE) of complex data. Then a baseband decoupling algorithm with hybrid beamforming structure has been proposed to eliminate the MC effect. Simulation results show that, in terms of MSE and bit error rate (BER), the proposed deep learning based MC modeling method has an impressive modeling accuracy and perfect performance of decoupling. [ABSTRACT FROM AUTHOR]

The directional borehole radar can accurately locate and image the geological target around the borehole, which overcomes the shortcomings that the conventional borehole radar can only detect the depth of the target and the distance from the borehole. The directional borehole radar under consideration consists of a transmitting antenna and four receiving antennas equally distributed on the ring in the borehole. The nonuniformity caused by the borehole and sonde, as well as the mutual coupling among the four receiving antennas, will have a serious impact on the received signal and then cause interference to the azimuth recognition for the targets. In this paper, Finite difference time domain (FDTD), including the subgrid, is applied to study these effects and interferences, and the influence of borehole, sonde, and mutual coupling among the receiving antennas is found. The results show that, without considering the sonde and the fluid in the borehole, the one transmitting and one receiving borehole radar system does not have resonance, but the wave pattern of the reflected wave will have obvious distortion. For the four receiving antennas of the borehole radar system, there is obvious resonance, which is caused by the multiple reflections between the receiving antennas. However, when the fluid in the borehole is water and the relative permittivity of the sonde is low to a certain extent, the resonance disappears; that is, the generation of resonance requires a large relative permittivity material between the receiving antennas. When the influence of the sonde is considered, the resonance disappears because the relative permittivity of the sonde is low, which makes the propagation speed of the electromagnetic wave between the antennas accelerate and lose the conditions for resonance. In addition, the diameters of the sonde and the circular array of the receiving antennas can affect the received signal: the higher the diameter of the sonde and the higher the diameter of the circular array are, the better the differentiation of the received signal. The development of the research provides scientific guidance for the design and application of borehole radar in the future.

A method is presented to analyze the maximum power transfer efficiency of a wireless power transfer system and its electromagnetic fields via spherical modes. The Z-parameter and Y-parameter for two coupled antennas are derived using the antenna scattering matrix and an addition theorem. In addition, formulas for calculating the maximum power transfer efficiency and optimum load impedance are presented. A formula is derived to calculate the electromagnetic field generated by a wireless power transfer system from the antenna scattering matrix. [ABSTRACT FROM PUBLISHER]

A compact dual-port, multiple input-multiple output (MIMO) antenna array for handheld devices is introduced. The antenna structure consists of two quarter wavelength monopole slots etched on the ground plane of a printed circuit board (PCB) and a meandered slot cut between them. The meandered slot not only reduces the coupling between the two slot antennas, but also improves the bandwidth and efficiency of the array by acting as a radiating parasitic element. Simulated and measured results show that the meandered isolating slot allows the antennas to achieve wider bandwidth, higher efficiency, higher isolation and better diversity performance, compared to other types of isolating slots. [ABSTRACT FROM PUBLISHER]

This letter proposes a new mode-based method for estimating the channel characteristics of a near-field multiple-input–multiple-output (MIMO). When an antenna array composed of a short electric dipole and a small solenoidal loop is used, a 2\,\times\,2 near-field MIMO can be effectively constructed according to the orthogonality of the TM10 and TE10 modes. By using the proposed method, the transmission characteristics of the MIMO and the mutual coupling effect at the antenna array can be easily calculated. In addition, the capacity of the MIMO can also be calculated by using the analysis results. [ABSTRACT FROM PUBLISHER]

The directional borehole radar can accurately locate and image the geological target around the borehole, which overcomes the shortcomings that the conventional borehole radar can only detect the depth of the target and the distance from the borehole. The directional borehole radar under consideration consists of a transmitting antenna and four receiving antennas equally distributed on the ring in the borehole. The nonuniformity caused by the borehole and sonde, as well as the mutual coupling among the four receiving antennas, will have a serious impact on the received signal and then cause interference to the azimuth recognition for the targets. In this paper, Finite difference time domain (FDTD), including the subgrid, is applied to study these effects and interferences, and the influence of borehole, sonde, and mutual coupling among the receiving antennas is found. The results show that, without considering the sonde and the fluid in the borehole, the one transmitting and one receiving borehole radar system does not have resonance, but the wave pattern of the reflected wave will have obvious distortion. For the four receiving antennas of the borehole radar system, there is obvious resonance, which is caused by the multiple reflections between the receiving antennas. However, when the fluid in the borehole is water and the relative permittivity of the sonde is low to a certain extent, the resonance disappears; that is, the generation of resonance requires a large relative permittivity material between the receiving antennas. When the influence of the sonde is considered, the resonance disappears because the relative permittivity of the sonde is low, which makes the propagation speed of the electromagnetic wave between the antennas accelerate and lose the conditions for resonance. In addition, the diameters of the sonde and the circular array of the receiving antennas can affect the received signal: the higher the diameter of the sonde and the higher the diameter of the circular array are, the better the differentiation of the received signal. The development of the research provides scientific guidance for the design and application of borehole radar in the future. [ABSTRACT FROM AUTHOR]

A new method for modeling correlated noise in receiving antenna arrays for direction-of-arrival (DOA) estimation is introduced. The array noise is divided into a coupled and an uncoupled components which originate from the array environment and the internal circuitry of the antenna elements, respectively. While the uncoupled noise power can be determined a priori and be removed from the array received power, the antenna mutual coupling in the coupled noise component can be decoupled in the same way as the antenna mutual coupling in the signals. This results in a very simple but effective MUSIC DOA estimation algorithm. Simulation results are presented to validate and demonstrate the performance of the new method. [ABSTRACT FROM PUBLISHER]