Metamaterial Integrated Folded Dipole Antenna with Low SAR for 4G, 5G and NB-IoT Applications

A High-Performance Circularly Polarized and Harmonic Rejection Rectenna for Electromagnetic Energy Harvesting

This paper presents a novel circularly polarized rectenna designed for efficient electromagnetic energy harvesting at the 2.45 GHz ISM band. A compact antenna structure is designed to achieve high performance in terms of radiation efficiency, axial ratio, directivity, effective area, and harmonic rejection over the entire bandwidth of the ISM frequency band. The optimized rectifier circuit enhances the RF harvested energy efficiency, with an AC-to-DC conversion efficiency ranging from 36% to 70% for low-level input power ranging from -10 dBm to 0 dBm. The stable output of DC power confirms the suitability of this design for various practical applications, including wireless sensor networks, energy harvesting power supplies, medical implants, and environmental monitoring systems. Experimental validation, which includes both the reflection coefficient and radiation patterns of the designed antenna, confirms the accuracy of the simulation. The study found that the proposed energy harvesting system has a high total efficiency ranging from 53% to 63% and is well-suited for low-power energy harvesting (0 dBm) from ambient electromagnetic radiation. The proposed circularly polarized rectenna is a competitive option for efficient electromagnetic energy harvesting, both as a standalone unit and in an array, due to its high performance, feasibility, and versatility in meeting various energy harvesting requirements. This makes it a promising and cost-effective solution for various wireless communication applications, offering great potential for efficient energy harvesting from ambient electromagnetic radiation.

Focusing on the Development and Current Status of Metamaterial Absorber by Bibliometric Analysis

In this paper, a total of 4770 effective documents about metamaterial absorbers were retrieved from the Web of Science Core Collection database. We scientifically analyzed the co-occurrence network of co-citation analysis by author, country/region, institutional, document, keywords co-occurrence, and the timeline of the clusters in the field of metamaterial absorber. Landy N. I.'s, with his cooperator et al., first experiment demonstrated a perfect metamaterial absorber microwave to absorb all incidents of radiation. From then on, a single-band absorber, dual-band absorber, triple-band absorber, multi-band absorber and broad-band absorber have been proposed and investigated widely. By integrating graphene and vanadium dioxide to the metamaterial absorber, the frequency-agile functionality can be realized. Tunable absorption will be very important in the future, especially metamaterial absorbers based on all-silicon. This paper provides a new research method to study and evaluate the performance of metamaterial absorbers. It can also help new researchers in the field of metamaterial absorbers to achieve the development of research content and to understand the recent progress.

Low specific absorption rate quad-port multiple-input-multiple-output limber antenna integrated with flexible frequency selective surface for WBAN applications

This paper presents the design and analysis of a multiple-input-multiple-output (MIMO) textile antenna for wireless body area network (WBAN) applications. The MIMO antenna is comprised of four identical modified rhombus-shaped monopole antenna elements of size of 0.57 λ 0 ×   0.57 λ 0 ×   0.015 λ 0 , where λ 0 is the wavelength calculated at the lowest operating frequency. The antenna is backed by a 6 × 6 frequency selective surface (FSS) of dimensions of 0.84 λ 0 ×   0.84 λ 0 ×   0.015 λ 0 to improve gain and to reduce specific absorption rate (SAR). The antenna has an impedance bandwidth (S 11 ⩽ −10 dB) of 8.8 GHz (2.8–11.6 GHz) and isolation of >19 dB between the resonating elements. In order to assess the MIMO antenna’s flexibility, the bending analysis is performed for various bending radii. The obtained diversity metrics are: envelope correlation coefficient <0.5 dB, diversity gain <10 dB, channel capacity loss <0.4 bits s−1 Hz−1, and total active reflection coefficient <−10 dB. The performance of the antenna with and without FSS is investigated for gain enhancement and SAR reduction. With the help of FSS, the antenna gain is increased to 8.44 dBi, and the SAR reduced from 6.99 Watt kg−1 to 0.0273 Watt kg−1. The FSS achieves the highest efficiency of 96%. The designed antenna is suitable for smart textile applications due to its low SAR, high gain, and wider impedance bandwidth.

A slotted plus-shaped antenna with a DGS for 5G Sub-6 GHz/WiMAX applications

A slotted plus-shaped patch antenna (PSPA) with defected ground structure (DGS) is modelled and proposed for 5G Sub-6 GHz and WiMAX applications by using computer simulation technology (CST) MWS suite. The PSPA incorporates a rectangular slotted plus-shaped metal patch and a DGS. The PSPA is designed on a Rogers RT5880 (lossy) substrate with a compact dimension of 20 × 35 × 0.79 mm ³ . Its reflection coefficient is -52.06 dB resonating at 3.12 GHz and operates over a wider bandwidth of 2.56 GHz (2.67-5.23 GHz) to accommodate suitable Sub-6 GHz bands. The PSPA has a good gain (2.44 dB), directivity (2.53 dBi), and VSWR (1.005) at 3.12 GHz with omnidirectional radiation characteristics. The maximum efficiency of the proposed PSPA is about 98% for almost loss free power radiation. The apex of estimated gain and directivity are 4.65 dB and 4.95 dBi. The impact of different physical parameters on the antenna performance has also been studied and analysed in this paper. Initially, the proposed PSPA has been investigated by using time domain (TD) solver of CST then again it is buttressed by applying frequency domain (FD) solver of CST. Furthermore, the design has also been verified by high-frequency structure simulator (HFSS) as well as FEKO (a computational electromagnetics software). All the simulators show a very good agreement in results.

A co-polarization-insensitive metamaterial absorber for 5G n78 mobile devices at 3.5 GHz to reduce the specific absorption rate

Specific absorption rate (SAR) by next-generation 5G mobile devices has become a burning question among engineers worldwide. 5G communication devices will be famous worldwide due to high-speed data transceiving, IoT-based mass applications, etc. Many antenna systems are being proposed for such mobile devices, but SAR is found at a higher rate that requires reduced for human health. This paper presents a metamaterial absorber (MMA) for SAR reduction from 5G n78 mobile devices at 3.5 GHz. The MMA is co-polarization insensitive at all possible incident angles to ensure absorption of unnecessary EM energies obeying the Poynting theorem for energy conservation and thus ensuring smooth communication by the devices. The unit cell size of the absorber is 0.114 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda$$\end{document}λ making it design efficient for array implementation into mobile devices. This absorber has achieved a minimum of 33% reduction of SAR by applying to the 5G n78 mobile phone model, equivalent to SAR by GSM/LTE/UMTS band mobile phones and making it suitable for SAR reduction from next-generation 5G mobile devices.

A Road towards 6G Communication—A Review of 5G Antennas, Arrays, and Wearable Devices

Next-generation communication systems and wearable technologies aim to achieve high data rates, low energy consumption, and massive connections because of the extensive increase in the number of Internet-of-Things (IoT) and wearable devices. These devices will be employed for many services such as cellular, environment monitoring, telemedicine, biomedical, and smart traffic, etc. Therefore, it is challenging for the current communication devices to accommodate such a high number of services. This article summarizes the motivation and potential of the 6G communication system and discusses its key features. Afterward, the current state-of-the-art of 5G antenna technology, which includes existing 5G antennas and arrays and 5G wearable antennas, are summarized. The article also described the useful methods and techniques of exiting antenna design works that could mitigate the challenges and concerns of the emerging 5G and 6G applications. The key features and requirements of the wearable antennas for next-generation technology are also presented at the end of the paper.