Search

In this paper, based on the three‐dimensional frame structure between the antenna unit and the ground, a decoupling method, the current phase decoupler method, is proposed for the 5 G smartphone multiunit frame antenna. Using this method in a dual‐unit antenna, the additional current path reverses the phase of the coupled current flowing through the ground to the adjacent unit, while weakening the coupled current intensity and significantly suppressing the coupling between the units. The measured results show that the coupling is less than −28 dB, and the maximum efficiency is 85.53% without adding any lossy components. In an eight‐unit smartphone antenna system, the coupling of adjacent units can also be reduced below −24.6 dB with a maximum efficiency of 82.17%. This method has significant advantages over the existing decoupling methods and can be used as the preferred decoupling scheme for the future 5 G smartphone multiunit frame antenna. [ABSTRACT FROM AUTHOR]

A compact eight‐element frame antenna array covering the 5G n79 frequency band (4.4–5.0 GHz) has been proposed in this paper. Considering the demands in the application of 5G ultrathin smartphones, the antenna unit has been miniaturized and designed with a low profile. Each antenna unit occupies a distance of 11.1 mm on the long edge, and the profile height of each unit is only 3 mm. The antenna array consists of 8 identical monopole antennas. By loading an inverted E‐shaped slot on the ground plane and arranging the positions of the antenna units reasonably without the need for a decoupling structure, the antenna can achieve a low profile and compact design. Simultaneously, it can achieve excellent isolation and cover the entire n79 frequency band. The processed eight‐element antenna array has a −6 dB bandwidth ranging from 4.38 to 5.19 GHz. The isolation between all antennas is better than −13.9 dB. The total efficiency is between 48.66% and 90.57%, with an average efficiency of 68.6%. The ECC (envelope correlation coefficient) is less than 0.066. The antenna array is characterized by its small size, low profile, simple structure, easy manufacturing, and excellent radiation performance. It holds significant application value in the design of MIMO antennas for 5G ultrathin smartphones. [ABSTRACT FROM AUTHOR]

An electric current flowing through a bimetallic coil heats it up, and due to thermal expansion, the coil either unwinds or winds depending on the direction of net heat transfer and the specific heat capacities of the metals used. This means that by relating a certain measure of its mechanical displacement with current, the bimetallic coil can be used as an ammeter. Thus, a mathematical model relating the current to the time taken by the bimetallic coil to unwind a fixed displacement was developed and verified through experiments, which show a good agreement between theoretical and experimental values.

The Courant-Friedrich-Levy stability condition has prevented the conventional finite-difference time-domain (FDTD) method from being effectively applied to conductive materials because of the fine mesh required for the conducting regions. In this paper, the recently developed unconditionally stable alternating-direction-implicit (ADI) FDTD is employed because of its capability in handling a fine mesh with a relatively large time step. The results show that the unconditionally alternating-direction-implicit-finite-difference time-domain (ADI-FDTD) method can be used as an effective universal tool in modeling a medium regardless of its conductivity. In addition, the unsplit perfectly matched layer combined with the ADI-FDTD method is implemented in the cylindrical coordinates and is proven to be very effective even with the cylindrical structures that contain open conducting media. Index Terms--Alternating-direction-implicit-finite-difference time-domain (ADI-FDTD) method, highly conductive materials, perfectly matched layer (PML).

An unconditionally stable finite-difference time-domain (FDTD) method in the cylindrical coordinate system is presented in this paper. In it, the alternating-direction-implicit (ADI) method is applied, leading to a cylindrical ADI-FDTD scheme where the time step is no longer restricted by the stability condition, but by the modeling accuracy. In difference from the conventional ADI method, in which the alteration is applied in each coordinate direction, the ADI scheme here performs alternations in the mixed coordinates so that only two alternations in solution marching are required at each time step in the three-dimensional formulation. In difference from its counterpart in the Cartesian coordinate system, the cylindrical ADI-FDTD includes an additional special treatment along the vertical axis of the cylindrical coordinates to overcome singularity. Theoretical proof of the unconditional stability is shown and numerical results are presented to demonstrate the effectiveness of the cylindrical algorithm in solving electromagnetic-field problems. Index Terms--Alternating-direction-implicit (ADI) method, cylindrical coordinate system, finite-difference time-domain (FDTD) method, unconditional stability.