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A compact multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) that is suitable for internet of things (IoT) sensor networks is proposed with reduced coupling between elements. Two rectangular-shaped DRAs have been placed on the opposite sides of a Rogers substrate and each is fed using a coplanar waveguide (CPW) feed with slots etched in a dedicated metal ground plane that is located under the DRA. Moreover, locating the elements at the opposite sides of the substrate has improved the isolation by 27 dB without the need to incorporate additional complex structures, which has reduced the overall antenna size. Furthermore, a dual band operation is achieved since each antenna resonates at two frequencies: 28 GHz and 38 GHz with respective impedance matching bandwidths of 18% and 13%. As a result, the corresponding data rates are also increased independently. In addition to the advantages of improved isolation, compact size and dual band operation, the proposed configuration offers a diversity gain (DG), envelope correlation coefficient (ECC) and channel capacity loss (CCL) of 9.98 dB, 0.007, 0.06 bits/s/Hz over the desired bands, respectively. A prototype has been built with good agreement between simulated and measured results.

A compact four-port multiple-input multiple-output (MIMO) staircase rectangular patch antenna with inverse U-shaped resonators and a modified defected ground structure (MDGS) is presented for dual-band wireless communication applications. The antenna integrates four identical radiating elements placed orthogonally to achieve low mutual coupling and enhanced diversity. Fabricated on an FR-4 substrate with dimensions of 38 × 38 × 1.6 mm 3 , the design operates over two bandwidths (|S₁₁|< − 10 dB) of 6.8–8.9 GHz and 10.3–12.0 GHz, resonating at 7.9 GHz and 11 GHz, respectively. The structure achieves peak gains of 7.36 dBi and 5.82 dBi. MIMO performance is validated with an ECC below 0.01, DG greater than 9.95 dB, CCL below 0.02 bits/s/Hz, isolation exceeding 25 dB, mean effective gain (MEG) between − 9 dB and − 6 dB, and low TARC values. Simulated and measured results exhibit strong agreement, confirming the antenna’s potential for compact high-performance wireless devices within micro- and nanoscale integrated systems. The proposed design addresses key challenges in MIMO systems, such as minimizing mutual coupling, achieving wide dual-band operation, and maintaining compact size for integration in modern wireless devices.

This article presents an ultra-compact (1.02λ × 1.02λ mm 2 ) and highly isolated 8-port MIMO antenna designed for NR-n46 and n79 bands, as well as licensed assisted access (LAA). A systematic study was performed to choose an optimal antenna (Design-3) among all designs (Design-1, Design-2, and Design-3) after systematic study (parametric study and circuit theory analysis) of Ref. design-1, Ref. design-2, Ref. design-3 and Ref. design-4. An optimal and proposed antenna geometry consists of two orthogonal radiators on the top and a novel ground plane (rectangular ring, centered annular ring and plus shaped slot) at the bottom of each corner of the dielectric substrate to create a perfectly matched 8-port antenna. The proposed antenna demonstrates a wideband frequency operation of 700 MHz within the 4.75–5.45 GHz range, specifically in the sub-6 GHz 5G band. It resonates at 5.2 GHz, achieving an isolation of 33 dB, a gain of 4.7 dB, and a radiation efficiency of 92.5%. The MIMO characteristics, including ECC, DG, TARC, MEG, and CCL, were evaluated and found to be within acceptable parameters. The antenna was fabricated, tested in a laboratory setting, and its performance was validated against simulated results.

In this paper, a portable tri-band MIMO antenna with 1 × 1 and 2 × 2 inputs and outputs is developed for wireless applications. A decagon-shaped ring and two U-shaped radiating structures make up the proposed antenna, which can generate three resonance frequencies. Without utilizing any decoupling structures, the suggested antenna achieves improved isolation. The coplanar waveguide structure supplies all of the antennas, which are printed on the front side of the FR-4 substrate, which has a surface area of 18 × 18 mm. The suggested antenna serves a wide range of applications, including WLAN (5.2 GHz), Wi-max (5.5 GHz), and 5G n34 band, with an impedance bandwidth of − 10 dB over 1.98–2.03 GHz, 3.55–3.70 GHz, and 4.8–6.4 GHz (2 GHz). For tri-band MIMO antenna, the gain is (0.28 dB, 1.3 dB and 2.7 dB) and efficiency is (80%, 83%, and 91.5%). For MIMO, tri-band antennas are placed in rotational symmetry with respect to the adjacent ports. Distance between MIMO tri-band antenna is 20 mm. Isolation for tri-band MIMO antennas is (− 40 dB, − 28.5 dB and − 27 dB). ECC for tri-band MIMO antenna is 0.003. The fabricated antenna and simulated results agree quite well. As a result, the suggested antenna can be employed for WLAN and 5G applications.

In this paper, a microstrip Wilkinson power divider (MWPD) based on particle swarm optimization (PSO) algorithm is designed, simulated, and fabricated using novel resonators. In addition, attenuators and open-ended stubs are incorporated to generate a broad cut-off band and reduce unwanted harmonics. The proposed power divider has a central frequency of 1 GHz. The performance of each used resonator is analyzed based on lumped-element circuit models.The L and C parameters of the equivalent circuit of the used resonators are predicted and optimized with the assistance of the PSO method. The subsequent phase was the fabrication of the proposed MWPD, after which its performance was evaluated in the light of the results obtained from the simulation. It was discovered that there was a high degree of concordance between the two. On the other hand, the fabricated circuit has several benefits, including a suitable S 12 of − 3.15 dB, a high return loss of less than − 24 dB at the operating frequency, a compact size of 0.058 λ g  × 0.064 λ g , and the ability to remove undesired harmonics. The results show a high level of suppression of the unwanted harmonics (up to the 16th harmonic) and a great responsiveness in the passband, while having very low ripple. As a result, the proposed circuit may be used in a wide variety of electronic devices, such as radar transmitter and receiver circuits, and many other high-frequency systems.

Fifth generation (5G) technology aims to provide high peak data rates, increased bandwidth, and supports a 1 millisecond roundtrip latency at millimeter wave (mmWave). However, higher frequency bands in mmWave comes with challenges including poor propagation characteristics and lossy structure. The beamforming Butler matrix (BM) is an alternative design intended to overcome these limitations by controlling the phase and amplitude of the signal, which reduces the path loss and penetration losses. At the mmWave, the wavelength becomes smaller, and the BM planar structure is intricate and faces issues of insertion losses and size due to the complexity. To address these issues, a dual-layer substrate is connected through the via, and the hybrids are arranged side by side. The dual-layer structure circumvents the crossover elements, while the strip line, hybrids, and via-hole are carefully designed on each BM element. The internal design of BM features a compact size and low-profile structure, with dimensions of 23.26 mm × 28.92 mm (2.17 λ0  ×  2.69 λ0), which is ideally suited for the 5G mmWave communication system. The designed BM measured results show return losses, Sii and Sjj, of less than −10 dB, transmission amplitude of −8 ± 2 dB, and an acceptable range of output phase at 28 GHz.

This work proposes a new compact triple-band triangular patch antenna for RF energy harvesting applications in IoT devices. It is realized on Teflon glass substrate with a thickness of 0.67 mm and a relative permittivity of 2.1. Four versions of this antenna have been designed and realized with inclinations of 0°, 30°, 60° and 90° to study the impact of the tilting on their characteristics (S11 parameter, radiation pattern, gain) and to explore the possibilities of their implementation in the architectures of electronic equipment according to the available space. The antenna is also realized on waterproof paper with a thickness of 0.1 mm and a relative permittivity of 1.4 for biomedical domain. All the antennas (vertical antenna, tilted antennas and antenna realized on waterproof paper) have a size of 39 × 9 mm2 and cover the 2.45 GHz and 5.2 GHz Wi-Fi bands and the 8.2 GHz band. A good agreement is obtained between measured and simulated results. Radiation patterns show that all the antennas are omnidirectional for 2.45 GHz and pseudo-omnidirectional for 5.2 GHz and 8.2 GHz with maximum measured gains of 2.6 dBi, 4.55 dBi and 6 dBi, respectively. The maximum measured radiation efficiencies for the three antenna configurations are, respectively, of 75%, 70% and 72%. The Specific Absorption Rate (SAR) for the antenna bound on the human body is of 1.1 W/kg, 0.71 W/kg and 0.45 W/kg, respectively, for the three frequencies 2.45 GHz, 5.2 GHz and 8.2 GHz. All these antennas are then applied to realize RF energy harvesting systems. These systems are designed, realized and tested for the frequency 2.45 GHz, −20 dBm input power and 2 kΩ resistance load. The maximum measured output DC power is of 7.68 µW with a maximum RF-to-DC conversion efficiency of 77%.

This article demonstrates a compact wideband four-port multiple-input-multiple-output (MIMO) antenna system integrated with a wideband metamaterial (MM) to reach high gain for sub-6 GHz new radio (NR) 5G communication. The four antennas of the proposed MIMO system are orthogonally positioned to the adjacent antennas with a short interelement edge-to-edge distance (0.19λmin at 3.25 GHz), confirming compact size and wideband characteristics 55.2% (3.25–5.6 GHz). Each MIMO system component consists of a fractal slotted unique patch with a transmission feed line and a metal post-encased defected ground structure (DGS). The designed MIMO system is realized on a low-cost FR-4 printed material with a miniature size of 0.65λmin × 0.65λmin × 0.02λmin. A 6 × 6 array of double U-shaped resonator-based unique mu-near-zero (MNZ) wideband metamaterial reflector (MMR) is employed below the MIMO antenna with a 0.14λmin air gap, improving the gain by 2.8 dBi and manipulating the MIMO beam direction by 60°. The designed petite MIMO system with a MM reflector proposes a high peak gain of 7.1 dBi in comparison to recent relevant antennas with high isolation of 35 dB in the n77/n78/n79 bands. In addition, the proposed wideband MMR improves the MIMO diversity and radiation characteristics with an average total efficiency of 68% over the desired bands. The stated MIMO antenna system has an outstanding envelope correlation coefficient (ECC) of <0.045, a greater diversity gain (DG) of near 10 dB (>9.96 dB), a low channel capacity loss (CCL) of <0.35 b/s/Hz and excellent multiplexing efficiency (ME) of higher than −1.4 dB. The proposed MIMO concept is confirmed by fabricating and testing the developed MIMO structure. In contrast to the recent relevant works, the proposed antenna is compact in size, while maintaining high gain and wideband characteristics, with strong MIMO performance. Thus, the proposed concept could be a potential approach to the 5G MIMO antenna system.

In this article, the compact, ultra-wideband and high-gain MIMO antenna is presented for future 5G devices operating over 28 GHz and 38 GHz. The presented antenna is designed over substrate material Roger RT/Duroid 6002 with a thickness of 1.52 mm. The suggested design has dimensions of 15 mm × 10 mm and consists of stubs with loaded rectangular patch. The various stubs are loaded to antenna to improve impedance bandwidth and obtain ultra-wideband. The resultant antenna operates over a broadband of 26.5–43.7 GHz, with a peak value of gain >8 dBi. A four-port MIMO configuration is achieved to present the proposed antenna for future high data rate devices. The MIMO antenna offers isolation <−30 dB with ECC of <0.0001. The antenna offers good results in terms of gain, radiation efficiency, envelop correlation coefficient (ECC), mean effective gain (MEG), diversity gain (DG), channel capacity loss (CCL), and isolation. The antenna hardware prototype is fabricated to validate the performance of the suggested design of the antenna achieved from software tools, and good correlation between measured and simulated results is observed. Moreover, the proposed work performance is also differentiated with literature work, which verifies that the suggested work is a potential applicant for future 5G compact devices operating over wideband and high gain.

In this article, a compact super-wideband flexible textile antenna is proposed. It operates over an extremely broad frequency range from 3.16 to 50 GHz. The proposed design is characterized by its simple geometry, consisting of an offset rectangular patch, which is incorporated with three slots to enhance its performance, while a circular parasitic patch is positioned on the opposite side of the substrate. The proposed antenna prototype is fabricated on a footprint of 30 mm × 25 mm × 1 mm, which measures an electrical dimension of 0.31λ 0  × 0.26λ 0  × 0.012λ 0 at 3.16 GHz. As per measurements, a wide bandwidth of 15.82:1 from 3.16 to 50 GHz is achieved with a peak gain of 7.70 dBi at 23.05 GHz. Furthermore, the ADS software is employed to create and analyze the equivalent circuit model of the designed antenna whose simulation studies are executed using CST software. The suggested antenna's overall performance is described by investigating the effects of structural bending and also proximity to the human body. Moreover, it provides acceptable values of specific absorption rate, ensuring lower absorption, which are under the safety standard limits for RF exposure. The measured results correlate with simulated results. Owing to its simple topology, compact size, super-wideband behavior, and high gain, endorse its suitability for low-power requirement applications in the real world.