In this study, we propose a design of a multi-band slot antenna array applicable for fourth-generation (4G) and fifth-generation (5G) smartphones. The design is composed of double-element square-ring slot radiators fed by microstrip-line structures for easy integration with radio frequency (RF)/microwave circuitry. The slot radiators are located on the corners of the smartphone printed circuit board (PCB) with an overall dimension of 75 × 150 mm2. The proposed multiple-input multiple-output (MIMO) antenna is designed to meet the requirements of 4G and 5G mobile terminals with essential bandwidth for higher data rate applications. For −10 dB impedance bandwidth, each single-element of the proposed MIMO design can cover the frequency ranges of 2.5–2.7 GHz (long-term evolution (LTE) 2600), 3.45–3.8 GHz (LTE bands 42/43), and 5.00–5.45 GHz (LTE band 46). However, for −6 dB impedance bandwidth, the radiation elements cover the frequency ranges of 2.45–2.82 GHz, 3.35–4.00 GHz, and 4.93–5.73 GHz. By employing the microstrip feed lines at the four different sides of smartphone PCB, the isolation of the radiators has been enhanced and shows better than 17 dB isolation levels over all operational bands. The MIMO antenna is implemented on an FR-4 dielectric and provides good properties including S-parameters, efficiency, and radiation pattern coverage. The performance of the antenna is validated by measurements of the prototype. The simulation results for user-hand/user-head impacts and specific absorption rate (SAR) levels of the antenna are discussed, and good results are achieved. In addition, the antenna elements have the potential to be used as 8-element/dual-polarized resonators.

Multi-Band MIMO Antenna Design with User-Impact Investigation for 4G and 5G Mobile Terminals

The design and development of a compact tapered slot antenna (TSA) for the fifth generation (5G) phased array communications is described in this manuscript. The proposed low-profile TSA element is designed on a Rogers RT 5880 (?=2.2 and ?=0.0009) dielectric to work in the frequency range from 21 to 23 GHz. The configuration of the employed TSA antenna elements is composed of a slot-line flare from a small gap to a large opening, matching to free space’s wave impedance. Eight TSA elements with well-defined endfire radiation patterns have been used on the top portion of a mobile-phone PCB to form a 1×8 linear phased array. The TSA elements are fed by hockey-stick baluns. In addition, the radiation performance and SAR characteristics of the phased array 5G antenna in the vicinity of user’s hand & head have been investigated in this study. The results show that the proposed design provides good characteristics in terms of S-parameters, antenna gain, efficiency, SAR, and beam steering, which fit the need of 5G cellular communications.

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Small-Size Tapered Slot Antenna (TSA) Design for use in 5G Phased Array Applications

An interesting stabilizing variant of the biconjugate A-orthogonal residual (BiCOR) method is investigated for solving dense complex non-Hermitian systems of linear equations arising from the Galerlcin discretization of surface integral equations in electromagnetics. The novel variant is naturally based on and inspired by the composite step strategy employed for the composite step biconjugate gradient method from the point of view of pivot-breakdown treatment when the BiCOR method has erratic convergence behaviors. Besides reducing the number of spikes in the convergence history of the norm of the residuals to the greatest extent, the present composite step BiCOR method can provide some further practically desired smoothing behavior towards stabilizing the numerical performance of the BiCOR method in the case of irregular convergence.

Investigating the Composite Step Biconjugate A-Orthogonal Residual Method for Non-Hermitian Dense Linear Systems in Electromagnetics

In this paper, a low-SAR metamaterial-embedded planar monopole antenna is introduced for a wireless communication system. A printed monopole antenna is designed for modern mobile, which operates in GSM, UMTS, LTE, WLAN, and Bluetooth frequency bands. A metamaterial structure is designed to use in the mobile handset with a multi-band printed monopole antenna. The finite integration technique of the CST microwave studio is used in this study. The measurement of antenna performances is taken in an anechoic chamber, and the SAR values are measured using COMOSAR system. The results indicate that metamaterial structure leads to reduce SAR without affecting antenna performance significantly. According to the measured results, the metamaterial attachment leads to reduce 87.7% peak SAR, 68.2% 1-g SAR, and 46.78% 10-g SAR compared to antenna without metamaterial.

Low-SAR metamaterial-inspired printed monopole antenna

─ The bistatic electromagnetic scattering from the composite model of a three-dimensional (3-D) arbitrarily shaped object located above a two -dimensional (2-D) Gaussian rough surface is analyzed in this work. The object suited above is assumed to be a perfect electric conductor (PEC) while the rough surface is dielectric. Firstly, the Poggio, Miller, Chang, Harrington, Wu and Tsai (PMCHWT) integral equations, electric field integral equation (EFIE) are implemented and extended on the rough surface and on the surface of the object respectively. Then, the method of moments (MoM) combined with Galerkin method is introduced to discretize the integral equations to the matrix form using RWG basis function. Due to the memory requirement and computational complexity of traditional MOM are 2 ( ) O N ( N is the number of unknowns), the rank based 3-D Multilevel UV method (3DMLUV) is employed to reduce memory and CPU time overhead. The 3DMLUV has been successfully applied in the scattering of PEC targets, however, when the object or rough surface become dielectric, the fast fill-in method proposed in Reference [19] often breaks down due to the oscillatory nature of the gradient of Green’s function. Therefore, the ACA is applied to speed up the filling of the impedance entries required in 3DMLUV because of its algebraic nature. The efficiency and accuracy of the proposed method are demonstrated in a variety of scattering problems. Index Terms Composite model, bistatic scattering, PMCHWT, 3DMLUV, ACA

A Hybrid 3DMLUV-ACA Method for Scattering from a 3-D PEC Object above a 2-D Gaussian Dielectric Rough Surface

One of the most important obstacles that portable antennas are facing is their harmful effect on the user's body. In this paper, besides proposing a UWB vest antenna with a bandwidth of at least 500MHz, we try to reduce the specific absorption ratio (SAR) due to the proposed antenna on the human body. In order to achieve the mentioned goal, we modeled the human body after designing the antenna. In order to have simulation results closer to reality, we have used a 3-layer model of the human body instead of the 1- layer model. In our model of the human body, all of the body parts, except the torso, are modeled with three layers of bone, fat, and muscle. Since the torso has a different structure from other body parts and is close to the place of the antenna feed, we modeled it using four layers of air, bone, fat and muscle. As the next step in our simulation process, the antenna was installed on the human body and then the antenna parameters and its SAR were obtained again. In the last stage, SAR due to the proposed antenna is reduced using metamaterial.

Design and SAR Reduction of the Vest Antenna using Metamaterial for Broadband Applications

─ An improved MM-PO-UV hybrid method is developed to calculate the bistatic scattering from the two-dimensional (2-D) composite model of an electrically large ship (ELS) on a one-dimensional (1-D) rough sea surface at a low grazing angle (LGA). The subdivision of the MM and PO region is performed flexibly according to the physical considerations. The MM region contains not only the ship but also a small portion of the neighboring sea region where the surface currents need to be modeled accurately. An iterative solution BiCGSTAB is adopted to solve the final matrix equation of a large dimension caused by the ELS. Then, a UV matrix decomposition technique is applied as the fast algorithm to accelerate the matrix-vector productions and the matrix elements filling in. The improved method makes it possible for the Monte-Carlo simulation of large-scale complex target/rough surface problems under an LGA. The accuracy is validated in comparison with the traditional MOM method. Index Terms ─ LGA, MM-PO hybrid method, target/rough surface scattering, UV.

A. A. Heydari

Papers

Design and SAR Reduction of the Vest Antenna using Metamaterial for Broadband Applications

An Improved MM-PO Method with UV Technique for Scattering from an Electrically Large Ship on a Rough Sea Surface at Low Grazing Angle