A compact four-port (2 × 2) millimeter-wave (mm-wave) microstrip MIMO antenna front-end is presented for 5G New Radio (NR) Internet of Things (IoT) edge and aerial connectivity in the FR2 bands. Rather than serving as a standalone electromagnetic structure, the proposed design targets short- to medium-range IoT gateway and UAV-assisted deployment scenarios where front-end hardware performance directly governs achievable link reliability and coverage. The antenna integrates a flower-shaped radiator with an evolved defected ground structure (DGS) combining a circular complementary split-ring resonator (CSRR), rotated rectangular slots, and cross-elliptical slots to achieve a wide impedance bandwidth, high realized gain, and strong inter-element isolation without multilayer superstrates or external decoupling networks. Fabricated on a 0.508-mm-thick Rogers RT/Duroid®5880 substrate with an overall footprint of 37.7 × 37.7 mm2, the antenna covers the 5G NR n258 (24.25-27.50 GHz) and n257 (26.50-29.50 GHz) bands, providing an aggregate impedance bandwidth of approximately 13.5 GHz. Measured results demonstrate a peak realized gain of 9.8 dBi, average gain of approximately 8.7 dBi across the operating band, radiation efficiency between 85%-88%, and inter-port isolation exceeding 26 dB. Excellent MIMO performance is achieved with an envelope correlation coefficient (ECC) below 0.002, diversity gain close to 10 dB, and low channel capacity loss. Beyond antenna characterization, a deployment-oriented link-budget analysis grounded in measured gain and efficiency, together with large-scale path loss modeling, is performed to translate the validated hardware performance into achievable link margins under realistic FR2 propagation conditions. The results confirm that the proposed MIMO front-end provides sufficient link feasibility for compact, high-capacity 5G mm-wave IoT edge devices operating in dense and aerial deployment environments.

Implantable devices play a vital role in IoT-based healthcare, creating the need for compact, multi-band antennas that support high data rates for biotelemetry. This study presents a miniaturized dual-band, dual-port MIMO implantable antenna designed for wireless capsule endoscopy (WCE) and deep tissue applications. The antenna is integrated within a capsule-type device and has compact dimensions of 11.5×6×0.6mm3. It operates in the Industrial, Scientific, and Medical (ISM) bands of 433.1–434.8 MHz and 902–928 MHz. The proposed antenna supports the transmission of high-quality images and video over a considerable distance. Miniaturization and high isolation are achieved using carefully designed meandered lines. This design avoids the use of shorting vias or ground-plane slots, which simplifies the structure and reduces back radiation. As a result, it eliminates the need for a complex decoupling network to enhance isolation. This antenna is the first reported MIMO implantable design to operate in the lower ISM bands while maintaining an ultra-compact size. Following a detailed simulation-based analysis, a prototype was fabricated. The measured results showed excellent agreement with simulations. The antenna provides impedance bandwidths of 61 MHz (466–405 MHz) and 112 MHz (846–958 MHz), and measured gains of –40.2 dBi and –35 dBi at 433 and 915 MHz, respectively. Specific absorption rate (SAR) analysis was conducted to ensure compliance with IEEE safety standards. A link margin study was also performed, demonstrating reliable communication for high data rates of 1, 78, and 120 Mbps, with a minimum coverage distance of 10 meters based on SAR constraints. To assess diversity performance, envelope correlation coefficient (ECC) and diversity gain (DG) were evaluated and found within acceptable limits. The antenna also exhibits pattern diversity at both operational bands. The proposed design offers a reliable and compact solution for high-data-rate, SAR-compliant biotelemetry in modern IoT-based healthcare systems.

Wideband millimeter-wave (mm-wave) coverage is essential for the high-speed, low-latency communication required in next-generation 5G New radio (NR) Internet of Things (IoT) systems. This study develops a T-shaped four-element, highly compact wideband multiple-input multiple-output (MIMO) antenna covering the mm-wave n260 (37–40 GHz) and n259 (42–43.5 GHz) bands for 5G NR IoT applications. The antenna is designed on a 0.76 mm-thick Rogers RO4350B substrate with overall dimensions of$28\times $28 mm2 ($3.3\times 3.3~\lambda 2$). For design simplicity, a T-shaped patch backed by a full-ground plane is devised to serve as the radiator of a single-element antenna with the dimensions of (Ls$\times $Ws) mm2, optimized through a systematic three-step design process for improved performance. Moreover, the design has evolved into a$4\times 4$orthogonal MIMO configuration, achieving improved gain, polarization diversity, and higher data rates, with each element exhibiting wideband characteristics across 11.5 GHz (36.5–48 GHz) with high gains of 9.8 dBi and 6.6 dBi at n260 and n259 5G mm-wave bands, respectively. Additionally, arc-shaped complementary split-ring resonators (CSRR) are integrated into the ground plane to significantly enhance the gain while effectively reducing mutual coupling, remarkably achieving a maximum gain of 9.8 dBi. Furthermore, the MIMO antenna exhibits an envelope correlation coefficient of less than 0.10 between any two MIMO elements encountering the required condition of ¡0.5, ensuring good diversity gain of 9.99 dB, minimum isolation of 18 dB, and total efficiency of 86% at mm-wave n260 band and 89% at mm-wave n259 band. The measured and simulated results are in good agreement, confirming its viability for future 5G mm-wave IoT devices.

The emergence of 5G and beyond 5G (B5G) technologies has paved the way for the interconnectivity of devices in the form of internet of things (IoT). This results in the transfer of huge amounts of data and requires systems (particularly antennas) capable of handling high data rates and exhibiting large channel capacity, high gain, and beam steerability to enhance the signal-to-noise ratio (SNR). However, many studies on antenna designs for 5G and IoT applications target some of the above properties and fail to incorporate all of them in a single design. This work proposes a massive multiple-input-multiple-output (mMIMO) sub-array formed by a linear combination of four dielectric resonator antennas (DRAs) in a 1 × 4 linear array. The DRA array is fed by three separate unequal corporate power dividers (to reduce the side lobe level), resulting in a 3 × 3 MIMO array offering a three-fold increase in channel capacity as compared to the single port array. The proposed subarray can generate three high-gain beams independently steerable in the desired directions. The proposed array operates in the lower sub-6 GHz band with a measured impedance bandwidth of 900 MHz (3.0 GHz to 3.9 GHz). The three ports, P1, P2, and P3, provide a measured maximum gain of 8.2, 7.8, and 6.8 dBi, with -18 dB of side lobe level (SLL). The measured inter-port isolation is better than 15 dB for all the ports resulting in the achievement of the envelope correlation coefficients lower than 0.15 and diversity gain (DG) greater than 9.5 dB in the band of interest. Additionally, the link budget analysis confirmed that the proposed mMIMO subarray can establish a reliable link up to 230 m, 260 m, and 175 m for ports P1, P2, and P3, respectively, with an input power of 21 dBm. To the best of the author’s knowledge, this is the first mMIMO subarray that has a 1 × 4 linear array arrangement and is fed by three independent ports, resulting in a 3 × 3 mMIMO subarray, suitable for the base stations, femtocell, and indoor access points applications in 5G and IoT scenarios.

The employment of broadband/dual-band ultrahigh frequency (UHF) radio-frequency identification (RFID) tag antennas contributes to the growth of RFID technology, with many potential implications, such as the increase of international trade, and reducing costs thereof. This study presents all reported articles on RFID tags for metal objects that can work seamlessly across different countries. Moreover, it addresses all available approaches to design of wideband/dual-band metal-mountable tag antennas and showcases the techniques used to expand the tag bandwidth. The relevant works were gathered by applying a designated query ‘(“tag antenna*” OR “RFID tag*”) AND (metal*) AND (“broadband” OR “wideband” OR “dual band” OR “tri band”)’ in three scientific research engines (Web of Science, IEEE Xplore, and Scopus). The final set is determined on the basis of the exclusion and inclusion criteria, revealing 38 articles. The selected papers were categorized into five groups based on the tag structure, and all techniques utilized to widen the bandwidth of each specific structure. This taxonomy attempts to provide a deeper insight into the considered topic through a comprehensive presentation. The bandwidth measurement criterion, which is 3-dB return loss (RL) bandwidth is selected due to showing an adequate reading distance on the edge of the bandwidth. In addition, the criterion clarifies the operation frequencies that facilitate the worldwide operation of the RFID technology. This article fosters adaptation of suitable regulations to support the use of RFID systems, and researchers to design proper metal-mountable tags, which must be assessed based on operating frequencies, performance, size, cost, and compatibility with the targeted applications.

Electromagnetic simulation tools have been playing an increasing role in the design of contemporary antenna structures. The employment of electromagnetic analysis ensures reliability of evaluating antenna characteristics but also incurs considerable computational expenses whenever massive simulations are involved (e.g., parametric optimization, uncertainty quantification). This high cost is the most serious bottleneck of simulation-driven design procedures, and may be troublesome even for local tuning of geometry parameters, let alone global optimization. On the one hand, globalized search is often necessary because the design problem might be multimodal (i.e., the objective function features multiple local optima) or a reasonably good initial design may not be available. On the other hand, the computational efficiency of popular algorithmic approaches, primarily, nature-inspired population-based algorithms, is generally poor. Combining metaheuristics procedures with surrogate modelling techniques and sequential sampling methods alleviates the problem to a certain extent but modelling of nonlinear antenna responses over broad frequency ranges is extremely challenging, and the aforementioned solutions are normally limited to rather simple structures described by a few parameters. This paper proposes a novel approach to global optimization of multi-band antennas. The major component of the presented framework is the knowledge-based inverse surrogate constructed at the level of response features (e.g., frequency and level locations of the antenna resonances). The surrogate facilitates decision-making process of inexpensive identification of the most promising regions of the parameter space, and a rendition of the good-quality initial design for further local tuning. Our methodology is validated using three examples of dual- and triple-band antennas. The average optimization cost is only 150 full-wave antenna analyses while ensuring precise allocation of the antenna resonances at the target frequencies. This performance is demonstrated superior over both local optimizers and population-based metaheuristics.

During the last five years, several methods have been proposed for handling nonlinear constraints using evolutionary algorithms (EAs) for numerical optimization problems. Recent survey papers classify these methods into four categories: preservation of feasibility, penalty functions, searching for feasibility, and other hybrids. In this paper we investigate a new approach for solving constrained numerical optimization problems which incorporates a homomorphous mapping between n-dimensional cube and a feasible search space. This approach constitutes an example of the fifth decoder-based category of constraint handling techniques. We demonstrate the power of this new approach on several test cases and discuss its further potential.