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In this paper, a dual-band 4-, 6-, and 8-element multiple-input multiple-output (MIMO) antenna arrays operating at the sub-6-GHz (LTE 42/43 and 46) bands for the fifth-generation (5G) smartphones are proposed. To realize these three MIMO applications in two LTE bands, miniaturized spiral and meander line-shaped strips coupled-fed patch antenna elements are printed on the front side of an FR4 system circuit board and are able to excite two resonance modes. Polarization and spatial diversity techniques are applied to these elements so that the enhanced isolation and reduced coupling effects can be attained. The proposed single antenna element besides 8-element antenna array has been fabricated and experimentally measured. Desirable simulated and measured S-parameters (reflection and transmission coefficients) are obtained for the antenna arrays over the working dual frequency bands. The diversity performance, such as the envelope correlation coefficient (ECC) and diversity gain (DG), has also been simulated and analyzed. Moreover, the performance results, antenna gain, and efficiency over the bands and radiation patterns at the specified resonant frequencies are also presented.

In this paper, an optimized circularly polarized (CP) antenna is proposed for operating in the LTE bands 42/43 applications. This CP antenna comprises three sections, the meander-line and L-shaped strip structures modeled on the front side of a Roger 3003 substrate, and on the back side a rotated H-shaped ground plane is printed. In order to further increase the antenna common bandwidth (CBW), that is the voltage standing wave ratio bandwidth (VRBW) and axial ratio bandwidth (ARBW), an offset-fed line on the front side and a shorting pin are used. A feasible solution of the optimized CP antenna with compact size is achieved by applying an optimization design methodology with a fitness function that takes into account the antenna performance parameters, CBW, or both the VRBW and ARBW in addition to the realized gain (RG). Two programs are operating in synchronous fashion for finding the optimal geometric antenna parameters, a particle swarm optimization (PSO) for implementing the fitness function in MATLAB and a CST MWS simulator tool for extracting the antenna performance parameters. The optimized antennas without and with shorting pin are obtained with a broadest CBW and feature of CP operation and an acceptable RG across the desired LTE 42 (3.4-3.6 GHz) and LTE 42/43 (3.4-3.8 GHz) band, respectively. The proposed two designed antennas, with and without shorting pin, are fabricated, and the measured results are in good agreement with the simulated ones. From measured results, a −10 B-S 11 impedance bandwidth (IBW) of 220 and 460 MHz (3.37-3.83 GHz), a 3-dB ARBW of 200 MHz (3.4-3.6 GHz) and 390 MHz (3.42-3.81 GHz) with respective maximum RG of 2.26 and 2.39 dBic are exhibited by the antennas without and with pin, respectively. The obtained 3-dB ARBWs and −10-dB IBWs make the proposed antennas entirely cover the LTE 42 or LTE 42/43 frequency bands.

This paper presents a dual wide-band band pass filter (DWB-BPF) by using two parallel, symmetrical micro-strip lines loaded by a centered resonator, consisting of a T- and a triangle-shaped geometry, attached at the lower and upper ends, respectively. The filter reveals good performance and both the passbands can be independently controlled by adjusting specific parts of the filter. The proposed BPF is simulated by using CST microwave studio package and the simulated result is verified experimentally with good agreement between the two results.  The fabricated prototype BPF demonstrates two passbands located at 2.3 GHz and 6.35 GHz center frequencies with 39% and 23.6% of 3-dB fractional bandwidth (FBW), respectively and a good insertion and return losses. The designed BPF can be targeted for wireless local area network (WLAN), WIFI and satellite communication systems.

In this paper, a patch antenna (PA) and its self-complementary structure, slot antenna (SA) are proposed and designed for directly matching the impedance of a rectifier at 2.45 GHz resonance frequency. The structures of these antennas comprise three sections, meandered-line, spiral, and a double-folded geometries, which make their geometrical parameters to be varied in easy manner according to design equations. In order to enhance both the desired level of a complex reflection coefficient of antenna at given resonance frequencies and the specified lower and higher frequencies constituting the impedance frequency bands, a new fitness function is presented. This fitness function is applied in designing broadband or multiband antennas having approximately perfect conjugate impedance matching with the impedance of a rectifier suitably used for RF Energy Harvesting (RFEH) application. An optimization design methodology based on two programs operating in synchronous manner, the particle swarm optimization (PSO) implemented in MATLAB simulation tool and a CST MWS Electromagnetic (EM) solver, is applied to the designed PA as an illustrative example. The simulation results reveal that our design methodology is helpful to obtain an optimized PA (OPA) having good impedance matching at the desired resonance frequency along with appropriate band. Measured result of the fabricated prototype is in good agreement with the simulated ones. Moreover, acceptable features such as small size, omnidirectional radiation, and broadband operation satisfy the (2.4-2.5 GHz) WLAN band, which strongly makes the OPA a good candidate for RFEH applications.