Metal metamaterials: The core of electrically-fed antenna multi-performance optimization

Abstract

Metamaterials, engineered materials with exceptional electromagnetic properties not found in nature, have emerged as a revolutionary technology for enhancing conventional electrically-fed antenna performance across multiple critical parameters. This paper comprehensively reviews the application of metal-based metamaterials as the core enabling technology for optimizing electrically-fed antenna characteristics. Key performance improvements demonstrated include: (i) Gain enhancement using zero-index, epsilon-near-zero (ENZ), mu-near-zero metamaterials, or metamaterial lenses/superstrates, achieving gains up to 22.4 dBi and directivity improvements; (ii) Bandwidth expansion overcoming the inherent narrow bandwidth limitations of traditional patch antennas, with techniques yielding bandwidths exceeding 64% and operational ranges covering 4−9.1 GHz; (iii) Isolation improvement in multiple input multiple output (MIMO) systems crucial for 5G/6G, utilizing metamaterial walls or decoupling structures to achieve isolation >28 dB and mutual coupling suppression exceeding 36 dB; (iv) Antenna miniaturization leveraging complementary double-negative metamaterials, capacitive loading, or slow-wave structures to achieve up to 60.7% size reduction while maintaining or enhancing performance; and (v) Radiation efficiency Improvement, particularly addressing challenges like losses in graphene plasmonic antennas using engineered ENZ metamaterial substrates. The paper details innovative designs such as Fabry−Pérot resonator antennas with chessboard metamaterial superstrates, hybrid metasurface arrays, and pattern-reconfigurable zeroth-order resonance metasurface antennas. Future prospects highlight the integration of metamaterials and electrically-fed antennas with 6G, terahertz technology, AI-driven adaptive beamforming, and conformal applications in stealth and autonomous systems, despite ongoing challenges in cost-effective manufacturing and electromagnetic control complexity. Metamaterials are conclusively positioned as a pivotal technology for next-generation high-performance, multifunctional, and miniaturized antenna systems.

Graphical abstract

Keywords

metal metamaterials / electrically-fed antennas / multi-performance optimization

1 Introduction

Research on metamaterials traces back to 1968 when Soviet scientist Veselago first proposed the concept of left-handed materials (LHMs) [1]. These materials possess negative permittivity (ε < 0) [2] and negative permeability (μ < 0) [3], predicting unique electromagnetic phenomena such as negative refraction [4], inverse Doppler effect, and inverse Cherenkov radiation [5]. However, constrained by the material synthesis technology of that era [6], this concept remained experimentally unverified for decades. It was not until the late 1990s that Pendry [7] of Imperial College London proposed an innovative structural design. By periodically arranging miniature metal wires [8] and split-ring resonators (SRRs) [9], he achieved equivalent negative permittivity [10] and negative permeability [11] in the microwave band, paving the way for experimental studies on LHMs. Subsequently, Professor David Smith [12] at the University of California, San Diego, building on Pendry’s work, successfully fabricated LHMs and observed negative refraction. This breakthrough rapidly attracted widespread attention in physics and engineering [13, 14].

In 2000, Professor R. Walser [15] from the University of Texas at Austin formally coined the term “metamaterials” to describe this class of artificially structured materials exhibiting extraordinary physical properties absent in natural materials [16]. The uniqueness of metamaterials lies in their ability to display anomalous physical characteristics, such as negative permittivity and negative permeability, through precise geometric design and dimensional control [17, 18], rather than chemical composition. These properties enable metamaterials to flexibly manipulate key electromagnetic wave parameters (amplitude [19], phase [20], and polarization [21]), thereby inducing a series of exotic physical phenomena [22]. With the rise of terahertz (THz) technology, the integration of metamaterials [23, 24] and THz technology emerged as a new research hotspot [25]. THz radiation occupies a unique band in the electromagnetic spectrum between microwaves and infrared [26]. Research in this band was long hindered by the scarcity of efficient THz sources [27] and detectors [28]. However, metamaterials provide diverse means for controlling THz wave amplitude [29], phase [30], polarization [31], and propagation [32], becoming crucial for developing THz functional devices. Terahertz time-domain [33] spectroscopy (THz-TDS) comprehensively characterizes the electromagnetic response of metamaterials [34], forming a synergistic relationship with metamaterial development and jointly advancing THz technology [35].

In the electrically-fed antenna domain, as shown in Fig. 1, metamaterial applications demonstrate revolutionary innovation [36]. Integrating metamaterials into antenna design enables significant improvements in gain [37], bandwidth [38], and isolation [39]. For instance, loading a metamaterial superstrate enhances antenna gain and directivity [40]. Utilizing metamaterial resonant properties expands bandwidth [41]. Designs based on metamaterial walls reduce coupling effects between antennas, improving isolation [42]. Furthermore, metamaterials play a vital role in antenna miniaturization, optimizing geometry and current distribution to reduce size without sacrificing performance [43]. They also improve radiation efficiency, enabling efficient operation over wider frequency ranges [44, 45].

Looking ahead, metamaterial antennas represent a cutting-edge frontier, driving innovation in wireless communications, radar detection, and smart devices through deep integration of materials science and electromagnetic theory. With 6G technology development and THz band exploration, metamaterial antennas are poised to play greater roles in high-frequency communication, smart structures, and green energy-saving applications. Although commercialization faces challenges like material processing costs and complex electromagnetic control, ongoing technological progress and cost reduction are expected to enable large-scale production. They will find widespread applications across various fields, serving as a core hub connecting the physical world and digital twins.

2 Metamaterial applications in electrically-fed antennas

2.1 Gain enhancement

In antenna design, metamaterials offer flexible integration: placed as a superstrate in front of/above the radiator [46], or embedded within the same substrate [47]. Adjusting their electromagnetic properties alters the radiation pattern, enhancing gain. Specifically, metamaterials boost gain via low-impedance properties [48], lens effects (high refractive index (HRI), gradient refractive index (GRIN), negative refractive index (NRI)) [49]. For example, loading a zero-index metamaterial (ZIM) layer on a microstrip patch antenna (MPA) increases gain by up to 8.57 dB (experimental data). Similarly, epsilon-near-zero (ENZ) and mu-near-zero (MNZ) metamaterials effectively enhance gain [50].

Different metamaterials offer distinct advantages: ZIM [51] and low-index metamaterials (LIM) concentrate radiated energy by altering the radiation pattern. ENZ/MNZ improve gain by enabling better impedance matching with free space, reducing reflection loss [52]. Low-impedance metamaterials minimize the air gap between antenna and metamaterial layer, enabling compact designs while maintaining gain [53]. Metamaterial lenses significantly improve directivity and gain via focusing effects [54], converting spherical waves to plane waves. Future research directions include exploring novel metamaterial structures for higher gain, combining metamaterials with other enhancement techniques [55] (e.g., multiple-input multiple-output (MIMO), beamforming), and developing metamaterial antenna systems for diverse frequency bands and applications [56].

For instance, Zheng’s team (AFEU) [57] studied simultaneous gain enhancement and radar cross-section (RCS) reduction in a Fabry−Pérot resonator antenna (FPRA) using a chessboard arranged metamaterial superstrate (CAMS) – traditionally conflicting objectives. They designed a CAMS based on two frequency selective surfaces (FSSs). The top surface reduces RCS via phase cancellation, while the bottom enhances gain based on FP cavity theory. The antenna schematic is shown in Figs. 2(a) and (b).

Results showed a 4.9 dB gain increase at 10.8 GHz, a 3-dB gain bandwidth of 9.4−11.1 GHz (16.58%), and significant RCS reduction over 8.0−18.0 GHz (peak reduction 39.4 dB). For arbitrary polarization, ~10 dB RCS reduction was achieved over 9.6−16.9 GHz (55.09%). In-band RCS was also reduced. Optimizing the CAMS structure, particularly the central aperture, improved impedance matching, further enhancing gain bandwidth and in-band RCS reduction shown in Figs. 2(c) and (d). This design is suitable for applications requiring low RCS and high gain (e.g., stealth platforms). The CAMS design is versatile and applicable to other antenna types. Figure 2(e) shows the prototype and the measurement environment.

Shaji and Anju [58] proposed an antenna design using a complementary metamaterial (CMTM) superstrate for broadband high gain. A unique 2 × 2 CMTM superstrate array was employed, with each unit featuring a complementary fractal G-shaped structure operating at 2.4 GHz. Fabricated on FR4 substrate (ε_r = 4.4, tanδ = 0.02), the unit was optimized for low reflection/high transmission over 2.2−3.2 GHz. The superstrate was placed above an MPA, with the optimal distance ~λ₀/11 (~11 mm at 2.4 GHz).

The operating principle relies on metamaterial properties, gain enhancement, and beam steering. The CMTM units achieve a near-zero imaginary part of refractive index over a wide bandwidth, reducing transmission loss. Interaction with the antenna’s radiated field enhances gain. Rotating the superstrate enables beam steering in the azimuth plane. This antenna exhibits several excellent characteristics. Firstly, within the frequency band of 2.2 GHz to 3.2 GHz, the antenna gain is enhanced by 2 dB to 5 dB, with a maximum gain enhancement of 5 dB (achieved at 2.35 GHz), realizing broadband gain enhancement. Secondly, the use of the metamaterial superstrate narrows the antenna’s beamwidth, thereby improving its directivity. Additionally, the antenna possesses beam steering capability; by rotating the metamaterial superstrate, beam steering can be achieved within the azimuth plane. Finally, the distance between the antenna and the metamaterial superstrate is optimized to λ₀/11 (where λ₀ is the free-space wavelength), ensuring optimal performance.

2.2 Bandwidth enhancement

Traditional patch antennas, while offering advantages like simple structure, ease of manufacture, and integration, have long been limited by their narrow bandwidth [59, 60]. Typically, traditional patch antennas have bandwidths of only 2% to 5% [61], severely restricting their application in systems requiring wide bandwidths [62]. To overcome this limitation, researchers have explored various methods to increase the bandwidth of these antennas [63]. These methods include using vias [64] and parasitic patches to introduce additional resonant points [65], thereby expanding bandwidth; and utilizing slots and bandgap structures to suppress surface wave propagation, reduce energy loss, and consequently improve radiation efficiency and bandwidth [66]. However, while these solutions improve bandwidth to some extent, they often increase antenna design complexity and volume, making it difficult to meet miniaturization and integration requirements. In this context, using metamaterials in various resonator unit forms presents a potential development strategy [67]. Specifically, metamaterials can expand antenna bandwidth by introducing additional resonant points, optimizing radiation patterns, and reducing energy loss. Simultaneously, due to their flexible design and tunability, metamaterials can achieve these performance improvements without significantly increasing antenna volume and complexity. Nevertheless, despite the significant potential of metamaterials in antenna design, their practical application still faces challenges [68]. For example, metamaterial fabrication processes are relatively complex and costly; and the integration methods with antennas need further optimization to ensure stability and reliability in real-world applications [69, 70].

Das and Sahu [71] designed a high-gain broadband resonant cavity antenna (RCA) in C-band using ray tracing. Artificial magnetic conductor (AMC) and square patches served as metamaterial units, laminated on a lossy commercial dielectric (ε_r = 4.4, t = 1.6 mm) to form a metasurface. A cylindrical dielectric resonator antenna (CDRA) feeding the cavity at 4.2 GHz (exciting HEM₁₁δ mode via 50Ω offset-coaxial feed) provided broadband high gain. The AMC-PRS layer (4 × 4 perfect electric conductor (PEC) grid + patches) was characterized via Ansys HFSS and Keysight ADS equivalent circuit. Optimizing unit size/array configuration yielded a 4 × 4 metasurface. Results: 22.4 dBi gain, ~5.1 GHz bandwidth, −10 dB impedance bandwidth over 4−9.1 GHz (72.72% ratio). Prototype testing confirmed simulations. Adding metasurface layers increased gain/bandwidth but added bulk.

Wang et al. [72] designed an innovative 2 × 1 dual-band MIMO antenna integrated with a metal line-based metamaterial wall (MLB-MW) [Fig. 3(a)]. Exploiting the MLB-MW’s mu-negative (MNG) property suppressed EM wave propagation, reducing coupling, and enhancing isolation. It also introduced resonances, extending bandwidth. Dual-band stop MLB-MW units were designed, with metal line length/layout controlling resonance. Optimal antenna-MLB-MW distance ensured resonance.

In the low-frequency band, mutual coupling reduces by 36 dB, while in the high-frequency band, it reduces by 11 dB, with corresponding |S₂₁| parameters below −15 dB and −20 dB respectively, fully satisfying 5G base stations’ high isolation requirements. Simultaneously, the operational bandwidth substantially extends: the low band expands from 3.54–4.01 GHz to 3.41–4.02 GHz (32% extension), and the high band expands from 4.72–5.08 GHz to 4.67–5.14 GHz (30% extension) [Fig. 3(b)]. Furthermore, the designed MIMO antenna maintains compact dimensions of 0.70λ₁ × 0.29λ₁ × 0.23λ₁ (λ₁: wavelength at lowest frequency), making it highly suitable for 5G base station scenarios. To validate the design methodology, an antenna prototype was fabricated and detailed measurements conducted in an anechoic chamber [Fig. 3(c)], showing good consistency with simulations, and confirming design feasibility/superiority. Radiation characteristics demonstrate excellent omnidirectionality in the xOz-plane at 3.6/4.8 GHz, with gain increasing at 270° (toward MLB-MW) and decreasing at 180° (yOz-plane rear), indicating superior radiation performance. This structurally simple, easily designed, and low-cost approach offers high practical value. The antenna shows strong 5G base station potential by meeting both high isolation and wide bandwidth requirements. Although introducing additional height, the MLB-MW uniquely achieves isolation enhancement and dual-band bandwidth expansion – an advancement unreported in prior studies. Future work may optimize the structure to reduce added height and explore applications in other wireless systems. In summary, through theoretical analysis, simulation, and experimental verification, this work comprehensively demonstrates the metamaterial wall-based dual-band MIMO antenna’s superior performance in isolation improvement and bandwidth enhancement, providing new design insights for 5G+ wireless systems.

Nie et al. [73] proposed a Hybrid Metasurface (HMS) antenna composed of a 4 × 4 array of square metal patches, fed by an H-shaped coupling slot and microstrip line [Fig. 4(a)]. To further enhance performance and meet practical application needs, a compact 2 × 2 antenna array was designed based on the HMS antenna unit. Adjacent units share edge patches, exciting additional low-frequency resonances to enhance the impedance bandwidth. To verify the design effect, the authors conducted detailed numerical simulations using the full-wave electromagnetic simulation software CST Microwave Studio and manufactured a 2 × 2 antenna array prototype for testing. The antenna prototype and Antenna measurement setup is shown in Figs. 4(b) and (c). Results show that the simulated impedance bandwidth of a single HMS antenna unit is 18.01% (4.96–5.94 GHz), while the impedance bandwidth of the 2 × 2 antenna array reached 28% (4.41–5.85 GHz), showing improvement over the single unit. Within the operating band, the array’s boresight gain is greater than 8.4 dBi, with a maximum gain of 13.4 dBi (simulated) and 12.1 dBi (measured). Furthermore, the radiation efficiency exceeds 80% (simulated) / 72% (measured) over the 4.6–5.6 GHz band [Fig. 4(d)]. Measurements also show that the boresight cross-polarization level is below −30 dB across the operating band, indicating good radiation characteristics. Compared to previously reported Metasurface (MS) antennas, the HMS antenna array is more compact while maintaining comparable or wider bandwidth, and the HMS unit has smaller size, lower cross-polarization level, and comparable gain.

In conclusion, the HMS antenna achieves broadband impedance matching by exciting dual-resonance modes and effectively suppresses surface waves through shorting pins, thereby significantly enhancing gain while reducing cross-polarization levels. The designed 2 × 2 antenna array features not only a compact structure but also excellent performance, making it highly suitable for 5G sub-6 GHz and WiFi systems. Furthermore, owing to its minimized dimensions, satisfactory performance, and ease of integration, the HMS antenna array serves as a promising candidate antenna for both 5G and WiFi applications.

Liu et al. [74] designed a single-layer vertically polarized (VP) metasurface antenna with broadband and omnidirectional radiation for 360° coverage [Fig. 5(a)]. Traditional omnidirectional antennas (dielectric resonator, monopole) have high profiles. Microstrip antennas offer low cost/profile but narrow bandwidth. Metasurface antennas, optimized via characteristic mode analysis (CMA), hold promise. CMA identified omnidirectional characteristic modes and analyzed current distributions. A 4 × 4 metal patch structure was proposed. Corner and edge patch sizes were adjusted to optimize mode behavior for effective single-probe excitation over a wide band. Probe and slot feeding were explored; single central probe feeding was chosen to reduce complexity/cost.

Results demonstrate that the optimized metasurface antenna exhibits high Characteristic Mode Significance (MS) and Modal Excitation Coefficient (MEC) over a broad frequency band, with the MS bandwidth of Characteristic Mode 3 significantly increased to over 60% [Fig. 5(b)]. Both simulations and measurements confirm an impedance bandwidth of 64% (simulated) and 64.2% (measured) within the 5.2–10.1 GHz range under the –10 dB criterion, accompanied by a gain of 5–7 dBi and consistently maintained excellent omnidirectional radiation patterns across the operating band, as illustrated in Fig. 5(c). These results validate the design effectiveness, confirming the antenna’s achievement of high impedance bandwidth and stable omnidirectional radiation over a wide spectrum. Compared to conventional omnidirectional patch antennas, the proposed design demonstrates distinct advantages in both bandwidth and structural simplicity. Consequently, this antenna architecture is well-suited for wireless communication systems requiring broadband omnidirectional radiation, such as indoor base stations and mobile communications, offering a novel antenna solution for the wireless communication field.

2.3 Isolation enhancement

Enhancing antenna isolation is crucial in wireless systems, especially for MIMO systems. It reduces mutual interference between elements, improving signal purity/quality and overall system performance. Common methods (hybrid techniques [75], resistive loading [76], EBG (Electromagnetic Band Gap [77]), DGS (Defected Ground Structure [78])) face challenges: design complexity, fabrication difficulty [79], added loss (resistive loading), frequency limitations [80]. Metamaterial-based isolation offers advantages: high isolation, potential gain enhancement, better efficiency, and reduced element spacing/edge distance [81].

Mark et al. [82] enhanced MIMO antenna isolation/gain using a metamaterial superstrate. Metamaterial units were printed on a substrate, assembled into a superstrate, and placed above the MIMO antenna. Two rectangular patch antennas with coaxial probe feed were designed. The superstrate reduces coupling by absorbing near-field magnetic components; units form DNG (Double Negative) metamaterial (ε < 0, μ < 0) in specific bands, further reducing coupling. It also creates a cavity effect, increasing reflectivity and gain. Results: > 10 dB isolation improvement (isolation > 24 dB) across WLAN band; peak gain increased from 6.3 dBi to 7.98 dBi; 3% bandwidth increase; efficiency > 84%. Measurements matched simulations. Envelope correlation coefficient (ECC) near zero confirms suitability for MIMO.

Khandelwal et al. [83] designed a compact 4-port CP MIMO diversity antenna using metamaterials and slow-wave structure. The chiral-shaped metamaterial with ring structure exhibited DNG properties, enhancing performance and reducing mutual coupling/size via slow-wave effect. Four identical microstrip lines (each with a port) embedded metamaterial units. Precise unit placement/spacing achieved high isolation, circular polarization (CP), and good gain. Simulations/measurements agreed. Performance: very low mutual coupling at resonance, high-quality CP radiation, satisfactory gain/diversity gain.

Tariq et al. [84] designed a compact four-port MIMO diversity antenna based on metamaterials, with the design progression illustrated in Fig. 6(a)(I). This antenna features circular polarization (CP) characteristics while effectively suppressing mutual coupling between ports. The design employs a chiral-shaped metamaterial unit embedded with a ring structure, fabricated on an FR-4 epoxy substrate. Multiple metamaterial units are implanted into the antenna’s ground plane: one at the center and two beneath each microstrip line. These metamaterial units serve dual functions: acting as a defected ground structure (DGS) to enhance antenna performance and incorporating a slow-wave structure to achieve both miniaturization and significant mutual coupling reduction. The slow-wave structure elongates the current path, enabling a more compact antenna at identical frequencies while simultaneously reducing port-to-port mutual coupling interference. The antenna comprises four identical microstrip lines, each corresponding to one port and embedded with metamaterial units. Through precise control of the metamaterial units’ positioning and spacing, the design achieves high isolation (> 28 dB), circularly polarized radiation, and satisfactory gain performance. The simulated reflection coefficient results in Fig. 6(a)(II) (S₁₁, S₂₂, S₃₃, and S₄₄) for the MIMO antennas show that the four antenna elements exhibit nearly identical performance, with a resonant frequency band covering 24.8 GHz to 26.15 GHz. Compared to the earlier two-element array, the bandwidth of the MIMO structure has narrowed, primarily due to near-field coupling effects between the antenna elements. Nevertheless, the authors note that the achieved bandwidth remains sufficient for millimeter-wave communication. Furthermore, the transmission coefficient results [as shown in Fig. 6(a)(III)] indicate good isolation between the different MIMO antenna ports. Specifically, the isolation between Antenna 1 and Antenna 2 is optimal across the entire operating band, with a minimum value of approximately −33 dB.

The S-parameters were measured using a Rohde and Schwarz ZVA 40 Vector Network Analyzer (VNA). Figure 6(b)(I) displays the measured reflection coefficients for Antenna 1 (Ant1) and Antenna 4 (Ant4). The results indicate that Ant1 operates in the frequency band of 24.7–26.4 GHz, achieving a –10 dB impedance bandwidth of 1.7 GHz. Similarly, Ant4 exhibits an operational band from 24.55 GHz to 26.5 GHz, with a wider impedance bandwidth of 1.95 GHz. Furthermore, the measured transmission coefficients in Fig. 6(b)(II) illustrate the isolation between Ant1 and Ant2, as well as between Ant1 and Ant3. A close agreement is observed between the simulated and measured data, with only minor discrepancies. These slight differences are primarily attributed to imperfections in the fabrication process and signal losses in the measurement cables. Comparison showed excellence in coupling suppression, CP performance, diversity. Flexible design applicable to different frequencies. Suitable for earth exploration satellites, radiolocation, radionavigation, space research.

Esmail et al. [80] proposed a dual-band MIMO antenna design employing a pentagonal monopole structure printed on a 0.508-mm-thick Rogers RT5880 substrate, achieving dual-band response at 5G’s 28/38 GHz frequencies with wideband characteristics. The antenna features compact physical dimensions of 5.5 mm × 5.4 mm × 0.508 mm (feedline excluded). The MIMO system comprises two symmetrically arranged radiating elements, with an embedded metamaterial array significantly reducing inter-element mutual coupling. A specifically designed dual-band metamaterial unit positioned between the radiating elements effectively enhances system isolation. Through optimization of the metamaterial unit’s dimensions and layout, high isolation levels of –39 dB at 28 GHz and –38 dB at 38 GHz were achieved. Comprehensive performance analysis including S-parameters, surface current distribution, radiation patterns, and gain demonstrates that compared to the metamaterial-free MIMO system, the metamaterial-embedded configuration exhibits outstanding mutual coupling suppression while maintaining favorable radiation characteristics and gain. Radiation efficiency exceeds 92% in both bands with omnidirectional radiation patterns. Critical metrics evaluation confirms exceptional performance: Envelope Correlation Coefficient (ECC) < 0.0001, Diversity Gain (DG) > 9.99 dB, Total Active Reflection Coefficient (TARC) < –22 dB, and Channel Capacity Loss (CCL) < 0.05 bit/s/Hz, indicating superior diversity performance suitable for high-speed data transmission systems.

Milias et al. [85] designed a compact monopole antenna [Fig. 7(a)] embedded with a complementary split-ring resonator (CSRR) for multiband operation. A rectangular patch placed beneath the monopole further reduces antenna size and enhances performance. Operating at 2.4–2.5 GHz, 2.9–4.8 GHz, and 5.1–6.5 GHz bands, the CSRR loading introduces new resonant modes. Meander-line structures exhibiting mu-negative (μ < 0) properties were designed as metamaterial units. Electromagnetic simulation tools optimized the meander-line geometry to achieve μ < 0 characteristics at target frequencies (2.4 GHz and 5.8 GHz) [Fig. 7(a)]. The optimized structures were integrated between two antennas to reduce coupling: one 2.4-GHz meander-line between antennas, and multiple 5.8-GHz meander-lines on the top and bottom layers of the antennas. These μ < 0 structures prevent electromagnetic wave propagation (real propagation constant) at specific frequencies, thereby suppressing inter-antenna coupling and achieving isolation enhancement through metamaterial-induced wave blocking. At 2.45 GHz, isolation improves from –11 dB to –26 dB; at 5.8 GHz, isolation enhances from –16 dB to –45 dB. The 5.8 GHz band demonstrates significant broadband isolation enhancement covering the entire 5–6 GHz range. The fabricated prototype of the two antennas and the measured S-parameters are shown in Fig. 7(b). The metamaterial integration minimally impacts antenna impedance matching and radiation efficiency, with radiation efficiency reduction limited to 2%–5%. This isolation enhancement solution adds no extra volume to the antenna platform, making it ideal for space-constrained applications.

Shabbir et al. [86] proposed a low-cost 16-port non-planar multiple-input multiple-output (MIMO) antenna system specifically designed for 5G applications, as illustrated in Fig. 8. The system is constructed around a 3D octagonal polystyrene block, with MIMO elements distributed across eight side faces while leaving the top and bottom surfaces vacant. Each MIMO antenna unit features a slotted microstrip patch design with stepped-chamfered feedlines and a defected ground structure (DGS), integrated on an FR-4 substrate measuring 22 mm × 20 mm to cover the 3.35–3.65 GHz 5G band. To enhance inter-element isolation, a near-zero-index epsilon-negative (NZI-ENG) metamaterial decoupling structure based on meander-lines was implemented on the bottom layer, working in conjunction with top-layer antenna units to achieve over 28 dB isolation for both cross and side-by-side element configurations. Furthermore, the authors validated key MIMO performance parameters through simulations and measurements: Total Active Reflection Coefficient (TARC) < –18 dB, Envelope Correlation Coefficient (ECC) < 0.1, and Channel Capacity Loss (CCL) < 0.3, all within acceptable ranges. The metamaterial unit’s design and analysis process – including geometric configuration, structural composition, and simulation setup – was detailed. Each unit combines square rings formed by meander-lines, T-shaped stubs, and circular split-rings, with HFSS simulations verifying effective stopband characteristics at 3.5 GHz. The authors also examined single-element design optimization, analyzing how patch geometry selection and ground plane modifications impact reflection coefficients.

In the implementation of the 16-port non-planar MIMO antenna system, the research team demonstrated the integration of antenna elements onto the octagonal polystyrene block, where copper sheets interconnect the ground planes of individual units to establish a common ground plane for all elements. The introduction of the NZI-ENG metamaterial decoupling structure effectively reduced mutual coupling between antenna elements, enhancing overall system performance. Simulation and measurement results validate that the antenna system achieves excellent impedance matching and low mutual coupling characteristics across the 3.5 GHz band.

2.4 Antenna miniaturization

Antenna miniaturization has been a key research focus for ~70 years. Early studies showed size reduction directly reduces bandwidth/efficiency due to impact on radiation Q-factor [87] and maximum achievable impedance bandwidth [88]. Recent efforts aim to shrink various antenna types while maintaining acceptable matching/bandwidth by altering electrical/physical properties [89]. Topology-based miniaturization techniques include: space-filling curves (fractals, meander lines) [90], engineered ground planes [91], reactive loading [92], slow-wave structures [93]. These optimize geometry [94], current distribution [95], electrical size [96]. Fractal antennas leverage self-similarity for longer current paths in limited space, lowering resonant frequency/size. Meander line antennas bend lines to fill space, used commercially (e.g., UHF RFID tags), but often sacrifice radiation efficiency. Material-based miniaturization uses: high-permittivity substrates, magnetodielectric substrates, metamaterials. High-ε substrates slow wave propagation, shrinking size but reduce efficiency and complicate matching. Magnetodielectric substrates aim to match intrinsic/air impedance for better efficiency but are difficult to realize. Metamaterials (artificial composites with ε < 0, μ < 0) improve small antenna performance (e.g., adding DNG shells to dipoles increases efficiency [97]). For broadband antennas, fractal trees/meander lines shrink size while maintaining bandwidth. For reconfigurable antennas, tunable elements (PIN diodes, reed switches) enable dynamic switching between configurations for multi-service platforms [98].

Thankachan et al. [99] specifically focused on complementary double-negative metamaterial (CDNG-MTM) structures, applying them to a circular microstrip patch antenna design as shown in Fig. 9(a) loading the CDNG-MTM structure successfully miniaturized the antenna, reducing its size by 60.7% while enabling dual-band operation at 2.4 GHz and 5.2 GHz – two widely used wireless communication bands. The design process began with a baseline circular patch antenna operating at 6.24 GHz, followed by CDNG-MTM integration to adjust its resonant frequencies and bandwidth. Simulation and experimental results demonstrate that the CDNG-MTM-loaded antenna achieves 10-dB impedance bandwidths of 1.63% at 2.4 GHz and 13.15% at 5.2 GHz, with key electrical parameters ka = 0.72 and Q_Chu = 4.07, confirming its classification as an electrically small antenna. Fabricated on low-cost FR4 substrate, the compact antenna (20 mm × 20 mm × 1.6 mm) exhibits peak gains of 3.8 dBi at 2.4 GHz and 2.9 dBi at 5.2 GHz [Fig. 9(b)]. Parametric analysis further reveals that the CDNG structure’s radius and slot length significantly influence resonant frequencies, whereas positional variations primarily affect higher-band resonance. Systematic adjustment of these parameters enables straightforward tuning across different wireless application bands. Finally, experimental validation of the antenna’s performance compared to conventional circular patch antennas confirmed that the CDNG-MTM-loaded antenna demonstrates significant advantages in size, operational frequency bands, and bandwidth. When benchmarked against other metamaterial-based microstrip patch antennas, this design also exhibits superior performance in compactness, bandwidth, and multiband characteristics.

Al-Bawri et al. [100] designed a metamaterial combining split-square and hexagonal unit cells, exhibiting mu-near-zero (MNZ), near-zero refractive index (NZRI), and epsilon-near-zero (ENZ) properties along the y-axis, while demonstrating wideband mu-negative (MNG) characteristics along the x-axis. By tuning electromagnetic parameters – permeability, permittivity, and refractive index – this metamaterial achieves effective control over electromagnetic wave propagation. Simulations and experimental verification confirm excellent impedance matching and broadband characteristics across the 26.4–29.1 GHz frequency range, making it highly suitable for 5G millimeter-wave communications.

Building upon this metamaterial, a 3 × 3 units MIMO antenna array was designed, as shown in Figs. 10(a) and (b), operating over the 24–30 GHz band with a continuous 6 GHz bandwidth. Through optimized element arrangement and metamaterial integration, the MIMO antenna achieves > 24 dB isolation with only 4 mm element spacing [Fig. 10(c)]. Furthermore, it demonstrates exceptional radiation performance: peak gain reaching 12.4 dBi, total efficiency exceeding 98%, and envelope correlation coefficient (ECC) < 0.0013 – indicating high diversity gain and channel capacity.

Juan et al. [101] proposed a miniaturized circularly polarized (CP) metasurface antenna unit utilizing capacitive loading technology, as shown in Fig. 11(a). By inserting a pair of capacitive-loaded strips diagonally across corner-truncated patches, a 56% unit size reduction was achieved. Building upon this miniaturized unit, a compact low-profile CP metasurface antenna was designed using a 4 × 4 array configuration with slot-coupled feeding. Compared to conventional CP metasurface antennas without capacitive strips, this design achieves 63% overall size reduction. Characteristic mode analysis (CMA) elucidated the CP radiation mechanism and demonstrated 6.5 dBi gain within the CP operating band. Parametric studies optimized antenna performance by analyzing how corner-truncation depth and strip length affect modal significance and phase difference, guiding the final design. The optimized antenna comprises two dielectric substrate layers: a top 4 × 4 miniaturized metasurface array and a bottom ground plane with slot-feed structure [Fig. 11(b)]. Simulations reveal 22% –10 dB impedance bandwidth (3–3.7 GHz) [Fig. 11(c)(I)], 8.5% 3 dB axial ratio (AR) bandwidth (3.33–3.63 GHz) [Fig. 11(c)(II)], and compact dimensions of 0.58λ₀ × 0.58λ₀ × 0.043λ₀ (λ₀: free-space wavelength), making it highly suitable for large-scale antenna array implementation.

2.5 Radiation efficiency improvement

Enhancing radiation efficiency is critical for antenna performance, directly impacting gain, bandwidth, and overall efficacy [102]. Primarily, high radiation efficiency enables more effective conversion of input power to radiated power, boosting gain for longer-range and clearer signal transmission [103]. Subsequently, radiation efficiency correlates strongly with bandwidth [104]; its improvement helps maintain stable performance across wider frequencies. Concurrently, in antenna miniaturization designs, sustaining radiation efficiency poses significant challenges as size reduction often compromises efficiency [105]. Thus, pursuing miniaturization necessitates focused efficiency enhancement to preserve holistic performance [106]. Finally, in multi-antenna systems (e.g., MIMO), while improved isolation reduces mutual interference, heightened radiation efficiency optimizes overall system performance. Consequently, radiation efficiency improvement constitutes a pivotal aspect of antenna design for achieving high-performance systems [107].

Traditional metal antennas excel in microwave bands but suffer significant radiation degradation in far-infrared regions due to thermal dissipation and skin effects, necessitating alternative materials. Graphene — a 2D honeycomb carbon crystal — attracts attention for supporting highly confined transverse magnetic (TM) surface plasmon polariton (SPP) waves. These SPP waves exhibit substantially reduced wavelengths compared to free space, facilitating device miniaturization, yet simultaneously causing notable radiation efficiency reduction. Amanatiadis et al. [108] analyzed substrate effects on graphene SPP wavelength and designed larger-footprint, higher-efficiency radiators for epsilon-negative (ENG) media. Theoretical and simulation studies revealed that theoretically ideal epsilon-near-zero (ENZ) dielectrics could significantly boost radiation efficiency. However, as natural ENZ media are nonexistent, artificial metamaterials were proposed. Comprising periodically arranged resonators, these metamaterials achieve tailored permittivity responses through geometric tuning.

For the novel graphene antenna, a modified OE1 resonator structure was employed. By incorporating interdigital capacitors and inductive spirals to reduce resonant frequency, greater resonator integration was achieved while maintaining compact dimensions. These resonators were embedded in a 3D array with silicon dioxide (SiO₂) background medium, forming an ENG/ENZ-characteristic metamaterial substrate. Full-wave simulations via the finite-difference time-domain (FDTD) method verified significant radiation improvement: compared to conventional SiO₂-based antennas, the new design exhibits over a fourfold increase in radiation efficiency.

Dhananjeyan [109] presents a compact (subwavelength scale) octagonal MIMO antenna system [Fig. 12(a)] designed for broadband applications operating in the 3.7–11 GHz frequency range. The antenna consists of two octagonal radiating elements, each fed by a 50 Ω microstrip line. By introducing a decoupling stub (25.6875 mm× 0.5 mm) between the radiators, the design achieves high isolation exceeding 15 dB despite an extremely close element spacing of only 3 mm. A modified ground plane structure is also employed to further extend the bandwidth and optimize impedance matching.

Performance measurements demonstrate excellent return loss (S₁₁/S₂₂ < –10 dB) [Fig. 12(b)(I)] and transmission isolation (S₁₂/S₂₁ < –15 dB) [Fig. 12(b)(II)] across the operating band, with a peak gain of 6.5 dBi. The MIMO performance metrics are outstanding, including a low envelope correlation coefficient (ECC < 0.2) [Fig. 12(c)(I)], high diversity gain (DG ≈ 9.8 dB) [Fig. 12(c)(II)], and low channel capacity loss (CCL ≈ 0.23 bps/Hz), indicating strong spatial diversity and channel reliability.

With advantages in size (16.2 mm × 25.6 mm), isolation performance, and wideband operation, this antenna outperforms many existing designs and is particularly suitable for space-constrained broadband wireless communication systems, such as 5G, UWB, and vehicular communications. The close agreement between simulation and experimental results confirms its practicality for real-world applications.

Esmail et al. [110] presents a metamaterial-based, highly isolated MIMO antenna designed for 5G millimeter-wave (mm wave) applications [Fig. 13(a)], featuring high gain and beam tilting capability. The antenna utilizes a bow-tie element fed by a substrate-integrated waveguide (SIW), operating in the 28 GHz band (26.5–29.5 GHz). To enhance gain, H-shaped metamaterial (MM) unit cells are integrated into the substrate, optimized via a trust-region (TR) gradient-based algorithm to achieve zero refractive index properties, resulting in a maximum gain of 11.2 dB at 29.2 GHz.

For MIMO implementation, two radiators are vertically arranged, and a modified square resonator (MSR) MM array is embedded between them to reduce mutual coupling and enable beam tilting. As shown in Figs. 13(b) and (c), through TR optimization, the design achieves exceptional isolation of up to 75 dB at 28.6 GHz and E-plane beam tilting of ±20° when switching excitation between ports. The antenna also demonstrates wide impedance bandwidth (26.2–30 GHz), low envelope correlation coefficient (ECC < 0.5 × 10^–4), and near-ideal diversity gain (≈ 10 dB). Experimental validation confirms good agreement between simulated and measured results. The proposed design offers a compact, low-profile, and high-performance solution for 5G mm Wave MIMO systems, outperforming existing designs in terms of isolation, gain, and beam steering capability.

2.6 Multifunctional metasurface antennas

Metasurface technology offers unique advantages for electromagnetic wave manipulation [111]. By integrating tuning mechanisms, dynamic metasurfaces further enhance radio wave control [112], demonstrating significant potential in satellite communications and near-field computational imaging [113]. However, traditional metasurface elements face efficiency limitations, particularly high ohmic losses during diode conduction states that substantially degrade overall radiation efficiency [114]. Conventional complementary electric-LC (CELC) elements exhibit efficiency challenges in radiation-ON/OFF states, especially high losses when current flows directly through conducting diodes [115].

To address this, Lin et al. [116] proposed an efficient reconfigurable metasurface element based on elliptical CELC structures [Fig. 14(a)]. The design incorporates waveguide-slot and back-cavity feeding structures to prevent direct current flow through diodes, significantly reducing ohmic losses. Simulation analysis validated the design’s feasibility, demonstrating substantial improvements in radiated power and reduced losses versus conventional elements in both diode states. Crucially, when half the diodes conduct, a 10-element dynamic metasurface antenna (DMA) achieves 75% radiation efficiency – a dramatic increase from 25% in traditional designs. Experimental measurements further verified practical performance: the proposed element achieves a 12 dB radiation gain difference between ON/OFF states, meeting critical DMA application requirements [Fig. 14(b)].

Wang et al. [117] proposed a novel miniaturized, aperture-shared, vertically polarized (VP), zeroth-order resonance (ZOR)-based metasurface antenna, as shown in Fig. 15(a). This antenna features pattern reconfigurability and is particularly suitable for 5G sub-6 GHz applications. The antenna design consists of a 3 × 3 units metasurface and a ground plane, printed on a two-layer F4BM220 substrate with a thickness of 20 mils per layer. Metallic screws are loaded at the four corners of the metasurface, serving as the shunt left-handed inductance for the mushroom units while also providing structural support. By inserting an SMA probe at the center, the parallel ZOR mode of the metasurface is excited to achieve VP omnidirectional radiation. U-shaped microstrip stubs are printed on the ground plane to introduce an additional resonant mode, thereby enhancing the impedance bandwidth. Furthermore, the antenna incorporates four metallic shorting vias with p−i−n diodes and their DC bias circuits implemented along the four sides of the metasurface, forming mushroom-like reflectors. By controlling the ON/OFF states of the p−i−n diodes, switching between omnidirectional and directional radiation patterns is achieved. The antenna’s operational principle is based on the excitation of the ZOR mode and its pattern reconfigurability. The mushroom units introduce the parallel ZOR mode through shunt left-handed inductance and series left-handed capacitance. Selecting an appropriate feeding method can excite this mode to realize VP omnidirectional radiation. Simultaneously, controlling the states of the p−i−n diodes alters the state of the mushroom-like reflectors, enabling switching of the radiation pattern, including omnidirectional coverage and eight horizontally scanned beams with 45° step increments.

This antenna possesses numerous excellent characteristics. Its compact size and low profile, as shown in Fig. 15(b), make it highly suitable for applications in space-constrained devices. Simultaneously, the antenna exhibits [Fig. 15(c)(I)] an 11.5% overlapping −10 dB impedance bandwidth, covering the B42/B43 LTE bands, meeting the 5G system’s demand for wider operating bandwidth. Under different radiation states, the antenna achieves a peak gain of 4.5 dBi [Fig. 15(c)(II)] and can realize omnidirectional coverage and 360° full-range beam scanning. Furthermore, the antenna design is flexible; by adjusting the size of the mushroom units and the ground plane, the tilted radiation pattern can be easily tuned.

The miniaturization and low-profile design of this antenna make it exceptionally well-suited for space-limited environments. Its wide bandwidth characteristic fulfills the 5G system’s requirement for high-speed data transmission. The pattern reconfigurability enables the antenna to flexibly switch radiation modes according to different application scenarios, thereby improving transmission quality and channel anti-interference capability. Additionally, the antenna design is simple, requiring neither complex multi-layer structures nor additional multi-port control circuits, thus reducing cost and complexity. Across different radiation states, the antenna consistently demonstrates good radiation performance, with both peak gain and radiation efficiency being relatively high.

Ren et al. [118] proposed an innovative broadband radar cross-section (RCS) reduction technique based on a composite metasurface, specifically targeting circularly polarized (CP) slot array antennas [Fig. 16(a)]. The antenna features a unique design comprising a multi-layered Frequency Selective Rasorber (FSR) integrated with a CP slot antenna loaded with a Polarization Rotation Reflecting Surface (PRRS). Positioned in the upper layer, the FSR absorbs out-of-band electromagnetic waves through its structure consisting of a lower Frequency Selective Surface (FSS) and an upper lossy layer; this lossy layer incorporates periodic metallic patterns with resistive loading for efficient wave absorption. The PRRS, loaded above the slot antenna, utilizes unit cells of metallic patterns printed on a dielectric substrate to convert incident linearly polarized (LP) waves into cross-polarized LP waves; arranged in a checkerboard configuration with a 180° phase difference between adjacent units, it achieves in-band RCS reduction via electromagnetic wave phase cancellation. As illustrated in Fig. 16(b), the antenna’s operation relies on dual RCS reduction mechanisms and CP radiation generation: the FSR provides out-of-band RCS reduction by absorbing arbitrarily polarized incident waves, while the PRRS enables in-band reduction through scattering cancellation. Simultaneously, a sequentially rotated feeding network at the antenna’s base delivers phase shifts of 0°, 90°, 180°, and 270° to generate CP radiation.

This antenna exhibits multiple superior characteristics, with its physical prototype shown in Fig. 16(a). Primarily, it achieves broadband RCS reduction with a bandwidth spanning from 3.2 GHz to 19.6 GHz, representing a 143.9% fractional bandwidth [Fig. 16(c)]. Secondly, the antenna maintains normal circularly polarized (CP) radiation at the center frequency of 12 GHz, demonstrating an axial ratio (AR) below 3 dB [Fig. 16(d)], which ensures well-preserved CP radiation performance. Furthermore, the design exhibits notable angular stability and polarization insensitivity, enabling effective mitigation against incident wave interference across varying angles and polarization states. The composite metasurface design successfully realizes broadband RCS reduction for the CP antenna while retaining excellent radiation characteristics, thereby addressing the narrow RCS reduction bandwidth limitation prevalent in current CP antenna research. Additionally, the antenna offers flexible design capabilities, allowing parameters of both the FSR and PRRS to be tailored according to specific requirements to achieve customized RCS reduction and radiation performance.

3 Prospects and challenges

Metamaterial antennas, as a frontier in antenna technology, are driving innovation in wireless communications, radar detection, and smart devices through the deep integration of materials science and electromagnetic theory. Current research has achieved prototypes of Dynamic Metasurface Array (DMA) antennas operating at 60 GHz millimeter-wave frequencies, enabling high-frequency reconfigurability via software-defined metamaterial elements. These antennas support real-time multi-beam switching and nanosecond-level beamforming, providing ultra-high-speed data transmission capabilities for 6G networks. For instance, a DMA prototype developed by UK scientists integrates high-speed interconnects and FPGA programming within a matchbox-sized volume, simultaneously generating multiple independent beams to ensure network coverage stability. Looking ahead, metamaterial antennas are poised to become critical infrastructure for 6G integrated space-air-ground networks, supporting high-bandwidth applications such as holographic imaging and telemedicine. Leveraging properties like negative refractive index and high transmittance, metamaterial antennas deliver breakthrough performance enhancements in 5G/6G scenarios. Experimental data indicates that metasurface antennas using magneto-dielectric composites can increase radiation efficiency by 30% while reducing inter-user interference through beamforming techniques. Notably, the integration of AI with metamaterials endows antennas with adaptive capabilities, allowing real-time network monitoring and dynamic beam steering to significantly improve spectral efficiency.

In military domains, the miniaturization and high-gain characteristics of metamaterial antennas have been applied in stealth aircraft and missile guidance systems. For example, a MIMO antenna based on zero-index metamaterials achieves a peak gain of 12.4 dBi in the 24−30 GHz band while maintaining over 99% radiation efficiency. For civilian applications, metamaterial antennas are reshaping communication device form factors: an airborne conformal antenna enhanced by metamaterial structures demonstrates 30% higher gain, 40% size reduction, and 50% coverage expansion. In autonomous driving, metamaterial antennas integrate sensing and communication functions, replacing traditional sensor systems to achieve “intelligent structure” breakthroughs.

Despite their immense potential, the commercialization of metamaterial antennas faces dual challenges of material processing costs and complex electromagnetic control. Current research focuses on two key directions: First, developing low-cost fabrication processes like hybrid 3D printing and micro-nano manufacturing for scalable metamaterial production; Second, advancing multi-physics coupled designs, such as heterogeneous integration of metamaterials with 2D materials (e.g., graphene) at terahertz frequencies. With global 6G R&D initiatives accelerating, metamaterial antennas are expected to achieve standardized applications around 2030, becoming core hubs connecting the physical world and digital twins.

As wireless technologies advance toward higher frequencies, the terahertz (THz) band emerges as a prime candidate for future ultra-high-speed communications due to its exceptional bandwidth potential. Metamaterial antennas for THz applications will become a major research focus, offering flexible electromagnetic response modulation essential for THz functional devices. However, high-frequency operation introduces challenges including signal attenuation and link losses. Future research will prioritize enhancing THz metamaterial antennas’ modulation efficiency and stability to overcome these barriers and enable practical deployment. Against a backdrop of increasing energy constraints, green and energy-efficient designs are becoming imperative. Future metamaterial antennas will emphasize low-power optimization through structural and material innovations while incorporating intelligent algorithms for dynamic energy management — adjusting operational states based on demand to minimize waste. This sustainable approach positions metamaterial antennas as key enablers for eco-friendly technology.

Manufacturing metamaterial antennas demands extreme precision, currently limiting large-scale adoption. Future efforts will refine fabrication techniques by leveraging 3D printing and micro-nano processing to ensure accuracy and consistency. As technology matures and costs decline, scalable production will transition metamaterial antennas from labs to widespread implementation. Concurrently, resolving compatibility issues with other systems and simplifying signal transmission/control complexities will enable holistic optimization, laying a robust foundation for ubiquitous metamaterial antenna applications.

Although metamaterial antennas demonstrate revolutionary performance potential, their future development still faces a series of severe challenges. Foremost among these is the bottleneck of high manufacturing costs and process complexity. The functionality of metamaterials heavily relies on the precise geometric structures of their subwavelength units, particularly in millimeter-wave and terahertz bands, where machining precision must reach micrometer-level accuracy. This makes traditional PCB processes inadequate, necessitating reliance on cutting-edge technologies such as electron-beam lithography, nanoimprinting, or high-precision 3D printing. Consequently, manufacturing costs remain high, production cycles are prolonged, and large-scale commercial applications are significantly hindered.

Furthermore, the co-optimization of multiple performance metrics presents another core challenge. Parameters such as gain, bandwidth, efficiency, and isolation in metamaterial antennas exhibit complex coupling relationships and even conflicts. For instance, miniaturization designs achieved through resonant principles often come at the expense of bandwidth, while the introduction of active devices for dynamic reconfigurability introduces additional ohmic losses, reducing radiation efficiency. Current designs heavily rely on empirical approaches and computationally intensive simulations, lacking systematic theoretical guidance and efficient multi-objective optimization tools. This makes the design of high-performance, multifunctional antennas akin to a difficult “tightrope walk”.

Lastly, the challenges of system integration and engineering applications cannot be overlooked. Efficiently integrating metamaterial antennas with active chips, feeding networks, and thermal management structures, while ensuring mechanical stability, thermal reliability, and electromagnetic compatibility in complex environments, is a critical threshold for practical application. For example, in reconfigurable designs, the introduction of control elements such as diodes alters surface current distribution, generates parasitic radiation, and increases system power consumption and thermal management difficulties. Future advancements must focus on developing heterogeneous integration technologies and multi-physics collaborative design methods to transform these advanced laboratory prototypes into truly reliable commercial products.

4 Summary

Metamaterials hold pivotal importance in conventional electrically-fed antenna applications, demonstrating critical significance across multiple dimensions. From a performance enhancement perspective, metamaterials’ unique electromagnetic properties provide opportunities for breakthroughs in antenna capabilities. They can significantly increase antenna gain, enabling antennas to deliver stronger signals under constrained power conditions, thereby expanding communication coverage and improving signal reception quality. Simultaneously, metamaterials allow precise control over radiation patterns, facilitating accurate beam focusing and directional transmission while reducing signal scattering in non-target directions. This substantially enhances communication efficiency and precision, proving particularly vital in complex electromagnetic environments and long-distance communications. Regarding miniaturization and integration, metamaterials play a crucial role. Traditional antennas face physical limitations in maintaining high performance while scaling down. Metamaterials, however, leverage their exceptional electromagnetic responses to transcend conventional design constraints, achieving smaller footprints and lighter weights without compromising — and often enhancing — performance. This attribute is essential for mobile devices, satellite communications, and aerospace applications, where it reduces power consumption, improves portability, and accommodates space-limited layouts.

Furthermore, metamaterials provide effective solutions for broadening operational bandwidth and enhancing inter-element isolation. As communication systems evolve toward multi-band and high-speed operation, metamaterials enable antennas to operate stably across wider frequency ranges, meeting diverse band requirements and simplifying system design. Concurrently, they improve isolation between antenna elements, minimizing signal interference and boosting overall performance and stability in multi-antenna systems. Additionally, the integration of metamaterials with dynamic reconfigurability grants antennas intelligent characteristics. Antennas can dynamically adjust beam direction, frequency, and polarization in response to environmental changes and communication demands, enabling adaptive communications and demonstrating exceptional flexibility and adaptability in complex, variable scenarios. From a cross-domain application standpoint, metamaterial antennas exhibit immense potential in emerging fields including radar detection, satellite communications, IoT, and autonomous driving. Their distinctive electromagnetic properties allow antennas to withstand more complex and demanding operational environments, propelling continuous innovation in related technologies, and establishing metamaterials as a pivotal driving force behind advancements in modern communication technology.

References

[1] R. Azim , M. T. Islam , and A. T. Mobashsher , Design of a dual band-notch UWB slot antenna by means of simple parasitic slits, IEEE Antennas Wirel. Propag. Lett. 12, 1412 (2013)

[2] C. Caloz,T. Itoh, Application of the transmission line theory of left-handed (LH) materials to the realization of a microstrip LH line, in: Proc. IEEE Antennas Propag. Soc. Int. Symp., pp 412–415, 2002

[3] A. Rahman , M. T. Islam , M. J. Singh , S. Kibria , and M. Akhtaruzzaman , Electromagnetic performances analysis of an ultra-wideband and flexible material antenna in microwave breast imaging: To implement a wearable medical bra, Sci. Rep. 6(1), 38906 (2016)

[4] S. M. Saeed , C. A. Balanis , C. R. Birtcher , A. C. Durgun , and H. N. Shaman , Wearable flexible reconfigurable antenna integrated with artificial magnetic conductor, IEEE Antennas Wirel. Propag. Lett. 16, 2396 (2017)

[5] M. T. Islam , M. Cho , M. Samsuzzaman , and S. Kibria , Compact antenna for small satellite applications, IEEE Antennas Propag. Mag. 57(2), 30 (2015)

[6] J. Batle , A. Farouk , O. Tarawneh , and S. Abdalla , Multipartite quantum correlations among atoms in QED cavities, Front. Phys. (Beijing) 13(1), 130305 (2018)

[7] K. Thenkumari , K. S. Sankaran , and J. Mathana , Design and implementation of frequency reconfigurable antenna for WiFi applications, Eng. Sci. 23(2), 876 (2023)

[8] G. Ma and P. Sheng , Acoustic metamaterials: From local resonances to broad horizons, Sci. Adv. 2, e1501595 (2016)

[9] X. Yu , . Mechanical metamaterials associated with stiffness, rigidity and compressibility: A brief review, Prog. Mater. Sci. 94, 114 (2018)

[10] H. Chen,C. T. Chan,P. Sheng, Transformation optics and metamaterials, Front. Phys. (Beijing) 7(3), 289 (2012)

[11] J. Tao and Q. Feng , Compact ultra-wideband MIMO antenna with half slot structure, IEEE Antennas Wirel. Propag. Lett. 16, 792 (2017)

[12] D. Cao , Y. Li , and J. Wang , Ka-band multibeam patch antenna array fed by spoof surface plasmon polariton butler matrix, IEEE Trans. Antennas Propag. 71(3), 2385 (2023)

[13] Y. T. Liu,K. W. Leung, 28 GHz substrate-integrated filtering dielectric resonator antenna array, IEEE Trans. Antenn. Propag. 70(10), 9900 (2022)

[14] S. Huang , . Compact broadband acoustic sink with coherently coupled weak resonances, Sci. Bull. 65(5), 373 (2020)

[15] L. Wang,S. Zhang,Y. Wang,Q. Zeng,Y. Zhang, Tunable and reconfigurable metasurfaces and metadevices, Front. Phys. (Beijing) 16(4), 43301 (2021)

[16] H. He, ., Topological negative refraction of surface acoustic waves in a Weyl phononic crystal, Nature 560(7716), 61 (2018)

[17] Z. Jiang,Z. Wang,L. Nie,X. Zhao,S. Huang, A low-profile ultrawideband slotted dipole antenna based on artificial magnetic conductor, IEEE Antennas Wirel. Propag. Lett. 21(4), 671 (2022)

[18] J. H. Ou , J. Huang , J. Liu , J. Tang , and X. Y. Zhang , High-gain circular patch antenna and array with introduction of multiple shorting pins, IEEE Trans. Antenn. Propag. 68(9), 6506 (2020)

[19] M. Wei , J. Wang , X. Wang , T. Liu , Y. Lu , and Y. Gao , Low-profile dual-band microstrip patch antenna with shorting pins, IEEE Antennas Wirel. Propag. Lett. 23(6), 1834 (2024)

[20] J. Kim and H. L. Lee , High gain planar segmented antenna for mm-wave phased array applications, IEEE Trans. Antenn. Propag. 70(7), 5918 (2022)

[21] Z. Liu , . Locally resonant sonic materials, Science 289(5485), 1734 (2000)

[22] X. Zhang and L. Zhu , Gain-enhanced patch antennas with loading of shorting pins, IEEE Trans. Antenn. Propag. 64(8), 3310 (2016)

[23] N. Fang , . Ultrasonic metamaterials with negative modulus, Nat. Mater. 5(6), 452 (2006)

[24] I. Khan , K. Zhang , L. Ali , and Q. Wu , Enhanced quad-port MIMO antenna isolation with metamaterial superstrate, IEEE Antennas Wirel. Propag. Lett. 23(1), 439 (2024)

[25] T. Shi,R. Chai,X. Chen,M. Li,T. Zhang,M. C. Tang, A low-profile, circularly polarized, metasurface-based antenna with enhanced bandwidth and stable high gain, IEEE Antennas Wirel. Propag. Lett. 22(2), 253 (2023)

[26] W. E. Liu , Z. N. Chen , and X. Qing , Broadband low-profile L-probe fed metasurface antenna with TM leaky wave and TE surface wave resonances, IEEE Trans. Antenn. Propag. 68(3), 1348 (2020)

[27] A. Valizade,C. Ghobadi,J. Nourinia,M. Ojaroudi, A novel design of reconfigurable slot antenna with switchable band notch and multiresonance functions for UWB applications, IEEE Antennas Wirel. Propag. Lett. 11, 1166 (2012)

[28] D. Samantaray , S. K. Ghosh , and S. Bhattacharyya , Modified slotted patch antenna with metasurface as superstrate for dual-band applications, IEEE Antennas Wirel. Propag. Lett. 22(1), 109 (2023)

[29] Y. Sun , Z. N. Chen , Y. Zhang , H. Chen , and T. S. P. See , Subwavelength substrate-integrated Fabry−Pérot cavity antennas using artificial magnetic conductor, IEEE Trans. Antenn. Propag. 60(1), 30 (2012)

[30] D. Samantaray,S. Bhattacharyya, A gain-enhanced slotted patch antenna using metasurface as superstrate configuration, IEEE Trans. Antenn. Propag. 68(9), 6548 (2020)

[31] Z. Wani , M. P. Abegaonkar , and S. K. Koul , High-low-epsilon biaxial anisotropic lens for enhanced gain and aperture efficiency of a linearly polarized antenna, IEEE Trans. Antenn. Propag. 68(12), 8133 (2020)

[32] M. Singh and M. S. Parihar , Gain improvement of Vivaldi MIMO antenna with pattern diversity using bi-axial anisotropic metasurface for millimeter-wave band application, IEEE Antennas Wirel. Propag. Lett. 22(3), 621 (2022)

[33] P. K. T. Rajanna,K. Rudramuni,K. Kandasamy, A high-gain circularly polarized antenna using zero-index metamaterial, IEEE Antennas Wirel. Propag. Lett. 18(6), 1129 (2019)

[34] K. Lu,Y. Ding,K. W. Leung, A new Fabry−Pérot resonator antenna fed by an L-probe, IEEE Trans. Antenn. Propag. 60(3), 1237 (2012)

[35] M. B. Kakhki , M. Mantash , A. Kesavan , M. M. Tahseen , and T. A. Denidni , Millimeter-wave beam-tilting Vivaldi antenna with gain enhancement using multilayer FSS, IEEE Antennas Wirel. Propag. Lett. 17(12), 2279 (2018)

[36] M. Li , X. Chen , A. Zhang , W. Fan , and A. A. Kishk , Split-ring resonator-loaded baffles for decoupling of dual-polarized base station array, IEEE Antennas Wirel. Propag. Lett. 19(10), 1828 (2020)

[37] T. Tuovinen , N. Tervo , and A. Parssinen , Analyzing 5G RF system performance and relation to link budget for directive MIMO, IEEE Trans. Antennas Propag. 65(12), 6636 (2017)

[38] J. Zhang,X. Ge,Q. Li,M. Guizani,Y. Zhang, 5G millimeter-wave antenna array: Design and challenges, IEEE Wirel. Commun. 24(2), 106 (2017)

[39] D. Liu , X. Gu , C. W. Baks , and A. Valdes-Garcia , Antenna-in-package design considerations for Ka-band 5G communication applications, IEEE Trans. Antennas Propag. 65(12), 6372 (2017)

[40] P. K. Mishra,D. R. Jahagirdar,G. Kumar, A review of broadband dual linearly polarized microstrip antenna designs with high isolation, IEEE Antennas Propag. Mag. 56(6), 238 (2014)

[41] M. Mirmozafari , G. Zhang , C. Fulton , and R. J. Doviak , Dual-polarization antennas with high isolation and polarization purity: A review and comparison of cross-coupling mechanisms, IEEE Antennas Propag. Mag. 61(1), 50 (2019)

[42] W. J. Chen,H. H. Lin, LTE700/WWAN MIMO antenna system integrated with decoupling structure for isolation improvement, in: 2014 IEEE Antennas and Propagation Society International Symposium (APSURSI), pp 689–690, IEEE, 2014

[43] M. Temiz , E. Alsusa , L. Danoon , and Y. Zhang , On the impact of antenna array geometry on indoor wideband massive MIMO networks, IEEE Trans. Antenn. Propag. 69(1), 406 (2021)

[44] C. He,X. C. Sun,X. P. Liu,M. H. Lu, Topological photonics in metamaterials, Front. Phys. (Beijing) 17(4), 42204 (2022)

[45] H. X. Xu , G. M. Wang , Z. Tao , and T. Cai , An octave-bandwidth Maxwell fish-eye lens antenna using three-dimensional gradient-index fractal metamaterials, IEEE Trans. Antenn. Propag. 62(9), 4823 (2014)

[46] S. Xiao , T. Wang , T. Liu , C. Zhou , X. Jiang , and J. Zhang , Active metamaterials and metadevices: A review, J. Phys. D 53(50), 503002 (2020)

[47] M. Farahani , J. Pourahmadazar , M. Akbari , M. Nedil , A. R. Sebak , and T. A. Denidni , Mutual coupling reduction in millimeter-wave MIMO antenna array using a metamaterial polarization-rotator wall, IEEE Antennas Wirel. Propag. Lett. 16, 2324 (2017)

[48] H. X. Xu , G. M. Wang , and T. Cai , Miniaturization of three-dimensional anisotropic zero-refractive-index metamaterials with application to directive emissions, IEEE Trans. Antenn. Propag. 62(6), 3141 (2014)

[49] H. X. Xu , G. M. Wang , M. Q. Qi , C. X. Zhang , J. G. Liang , J. Q. Gong , and Y. C. Zhou , Analysis and design of two-dimensional resonant-type composite right left-handed transmission lines with compact gain-enhanced resonant antennas, IEEE Trans. Antenn. Propag. 61(2), 735 (2013)

[50] Z. Tao,D. Bao,H. X. Xu,H. F. Ma,W. X. Jiang,T. J. Cui, A millimeter-wave system of antenna array and metamaterial lens, IEEE Antennas Wirel. Propag. Lett. 15, 370 (2016)

[51] A. K. Dwivedi , N. K. Narayanaswamy , K. K. V. Penmatsa , S. K. Singh , A. Sharma , and V. Singh , Circularly polarized printed dual port MIMO antenna with polarization diversity optimized by machine learning approach for 5G NR n77/n78 frequency band applications, Sci. Rep. 13(1), 13994 (2023)

[52] M. S. Sharawi , Current misuses and future prospects for printed multiple-input, multiple-output antenna systems, IEEE Antennas Propag. Mag. 59(2), 162 (2017)

[53] R. Li , G. DeJean , M. M. Tentzeris , J. Papapolymerou , and J. Laskar , Radiation pattern improvement of patch antennas on a large-size substrate using a compact soft-surface structure and its realization on LTCC multilayer technology, IEEE Trans. Antenn. Propag. 53(1), 200 (2005)

[54] J. Li , Y. Yuan , Q. Wu , and K. Zhang , Bi-isotropic Huygens’ metasurface for polarization-insensitive cross-polarization conversion and wavefront manipulation, IEEE Trans. Antenn. Propag. 72(3), 2445 (2024)

[55] R. Gonzalo , P. de Maagt , and M. Sorolla , Enhanced patch-antenna performance by suppressing surface waves using photonic-bandgap substrates, IEEE Trans. Antenn. Propag. 47, 2131 (1999)

[56] H. Boutayeb and T. A. Denidni , Gain enhancement of a microstrip patch antenna using a cylindrical electromagnetic crystal substrate, IEEE Trans. Antenn. Propag. 55(11), 3140 (2007)

[57] Y. Zheng , . Wideband gain enhancement and RCS reduction of Fabry−Pérot resonator antenna with chessboard arranged metamaterial superstrate, IEEE Trans. Antennas Propag. 66(2), 590 (2018)

[58] B. K. A. Shaji,P. Anju, Complementary metamaterial superstrate for wide band high gain antenna, in: Proc. IEEE Wireless Antenna Microw. Symp., Rourkela, India, pp 1–5, 2022

[59] F. Yang and Y. Rahmat-Samii , Microstrip antennas integrated with electromagnetic bandgap (EBG) structures: A low mutual coupling design for array applications, IEEE Trans. Antenn. Propag. 51(10), 2936 (2003)

[60] A. Jafargholi , A. Jafargholi , and J. H. Choi , Mutual coupling reduction in an array of patch antennas using CLL metamaterial superstrate for MIMO applications, IEEE Trans. Antenn. Propag. 67(1), 179 (2019)

[61] Y. Cho , J. J. Kim , D. H. Kim , S. Lee , H. Kim , C. Song , S. Kong , H. Kim , C. Seo , S. Ahn , and J. Kim , Thin PCB-type metamaterials for improved efficiency and reduced EMF leakage in wireless power transfer systems, IEEE Trans. Microw. Theory Tech. 64(2), 353 (2016)

[62] T. Cai , G. M. Wang , X. F. Zhang , Y. W. Wang , B. F. Zong , and H. X. Xu , Compact microstrip antenna with enhanced bandwidth by loading magneto-electro-dielectric planar waveguided metamaterials, IEEE Trans. Antenn. Propag. 63(5), 2306 (2015)

[63] M. Stocchi , Z. Cao , C. H. Joseph , T. Voss , D. Mencarelli , L. Pierantoni , C. B. Kaynak , J. Hebeler , T. Zwick , M. Wietstruck , and M. Kaynak , Gain enhancement of BiCMOS on-chip sub-THz antennas by mean of meta-cells, Sci. Rep. 12(1), 3946 (2022)

[64] X. M. Yang , X. G. Liu , X. Y. Zhu , and T. J. Cui , Reduction of mutual coupling between closely packed patch antenna using waveguide metamaterials, IEEE Antennas Wirel. Propag. Lett. 11, 389 (2012)

[65] A. M. Patel,A. Grbic, A printed leaky-wave antenna based on a sinusoidally-modulated reactance surface, IEEE Trans. Antenn. Propag. 59(6), 2087 (2011)

[66] R. W. Ziolkowski , . Composite medium with simultaneously negative permeability and permittivity, IEEE Trans. Antenn. Propag. 51(7), 2546 (2003)

[67] A. Dadgarpour , M. Sharifi Sorkherizi , and A. A. Kishk , High-efficient circularly polarized magnetoelectric dipole antenna for 5G applications using dual-polarized split-ring resonator lens, IEEE Trans. Antenn. Propag. 65(8), 4263 (2017)

[68] Y. Zhang,J. Y. Deng,M. J. Li,D. Sun,L. X. Guo, A MIMO dielectric resonator antenna with improved isolation for 5G mm-wave applications, IEEE Antennas Wirel. Propag. Lett. 18(4), 747 (2019)

[69] L. Sun , Y. Li , Z. Zhang , and H. Wang , Self-decoupled MIMO antenna pair with shared radiator for 5G smartphones, IEEE Trans. Antenn. Propag. 68(5), 3423 (2020)

[70] M. Farahani , J. Pourahmadazar , M. Akbari , M. Nedil , A. R. Sebak , and T. A. Denidni , Mutual coupling reduction in millimeter-wave MIMO antenna array using a metamaterial polarization-rotator wall, IEEE Antennas Wirel. Propag. Lett. 16, 2324 (2017)

[71] S. Das and S. Sahu , Design of high gain, broadband resonant cavity antenna with meta-material inspired superstrate, AEU Int. J. Electron. Commun. 100, 39 (2019)

[72] H. Wang , Q. Zheng , Q. Li , and X. X. Yang , Isolation improvement and bandwidth enhancement of dual-band MIMO antenna based on metamaterial wall, IEEE Antennas Wirel. Propag. Lett. 24(5), 1144 (2025)

[73] N. S. Nie,X. S. Yang,Z. N. Chen,B. Z. Wang, A low-profile wideband hybrid metasurface antenna array for 5G and WiFi systems, IEEE Trans. Antenn. Propag. 68(2), 665 (2020)

[74] S. Liu , D. Yang , Y. Chen , K. Sun , X. Zhang , and Y. Xiang , Design of single-layer broadband omnidirectional metasurface antenna under single mode resonance, IEEE Trans. Antenn. Propag. 69(10), 6947 (2021)

[75] S. S. Al-Bawri , M. T. Islam , M. S. Islam , M. J. Singh , and H. Alsaif , Massive metamaterial system-loaded MIMO antenna array for 5G base stations, Sci. Rep. 12(1), 14311 (2022)

[76] O. Luukkonen,S. I. Maslovski,S. A. Tretyakov, A stepwise Nicolson–Ross–Weir-based material parameter extraction method, IEEE Antennas Wirel. Propag. Lett. 10, 1295 (2011)

[77] F. Arshad,A. Ahmad,Y. Amin,M. A. B. Abbasi,D. Y. Choi, MIMO antenna array with the capability of dual polarization reconfiguration for 5G mm-wave communication, Sci. Rep. 12(1), 18298 (2022)

[78] H. Huang,X. Li,Y. Liu, 5G MIMO antenna based on vector synthetic mechanism, IEEE Antennas Wirel. Propag. Lett. 17(6), 1052 (2018)

[79] E. G. Larsson , O. Edfors , F. Tufvesson , and T. L. Marzetta , Massive MIMO for next generation wireless systems, IEEE Commun. Mag. 52(2), 186 (2014)

[80] B. A. Esmail and S. Koziel , High isolation metamaterial-based dual-band MIMO antenna for 5G millimeter-wave applications, AEU-Int. J. Electron. Commun. 158, 154470 (2023)

[81] P. Kumar , T. Ali , and M. M. Pai , Electromagnetic metamaterials: A new paradigm of antenna design, IEEE Access 9, 18722 (2021)

[82] R. Mark , N. Rajak , K. Mandal , and S. Das , Metamaterial based superstrate towards the isolation and gain enhancement of MIMO antenna for WLAN application, AEU Int. J. Electron. Commun. 100, 144 (2019)

[83] M. K. Khandelwal , Metamaterial based circularly polarized four-port MIMO diversity antenna embedded with slow-wave structure for miniaturization and suppression of mutual coupling, AEU Int. J. Electron. Commun. 121, 153280 (2020)

[84] S. Tariq,S. I. Naqvi,N. Hussain,Y. Amin, A metasurface-based MIMO antenna for 5G millimeter-wave applications, IEEE Access 9, 51805 (2021)

[85] C. Milias , R. B. Andersen , P. I. Lazaridis , Z. D. Zaharis , B. Muhammad , J. T. B. Kristensen , A. Mihovska , and D. D. S. Hermansen , Miniaturized multiband metamaterial antennas with dual-band isolation enhancement, IEEE Access 10, 64952 (2022)

[86] T. Shabbir,M. T. Islam,S. S. Al-Bawri,R. W. Aldhaheri,K. H. Alharbi,A. J. Aljohani,R. Saleem, 16-port non-planar MIMO antenna system with near-zero-index (NZI) metamaterial decoupling structure for 5G applications, IEEE Access 8, 157946 (2020)

[87] X. Gao , O. Edfors , F. Tufvesson , and E. G. Larsson , Massive MIMO in real propagation environments: Do all antennas contribute equally, IEEE Trans. Commun. 63(11), 3917 (2015)

[88] J. M. Gonzalez-Arbesu , S. Blanch , and J. Romeu , Are space-filling curves efficient small antennas, IEEE Antennas Wirel. Propag. Lett. 2(1), 147 (2003)

[89] J. Zhu , A. Hoorfar , and N. Engheta , Peano antennas, IEEE Antennas Wirel. Propag. Lett. 3(1), 71 (2004)

[90] D. Manteuffel and R. Martens , Compact multimode multielement antenna for indoor UWB massive MIMO, IEEE Trans. Antenn. Propag. 64(7), 2689 (2016)

[91] D. Guha , M. Biswas , and Y. M. Antar , Microstrip patch antenna with defected ground structure for cross polarization suppression, IEEE Antennas Wirel. Propag. Lett. 4(1), 455 (2005)

[92] S. Li , Z. N. Chen , T. Li , F. H. Lin , and X. Yin , Characterization of metasurface lens antenna for sub-6 GHz dual-polarization full-dimension massive MIMO and multibeam systems, IEEE Trans. Antenn. Propag. 68(3), 1366 (2020)

[93] P. L. Chi , R. Waterhouse , and T. Itoh , Antenna miniaturization using slow wave enhancement factor from loaded transmission line models, IEEE Trans. Antenn. Propag. 59(1), 48 (2011)

[94] C. R. Rowell,R. D. Murch, A capacitively loaded PIFA for compact mobile telephone handsets, IEEE Trans. Antenn. Propag. 45(5), 837 (1997)

[95] R. Azadegan,K. Sarabandi, A novel approach for miniaturization of slot antennas, IEEE Trans. Antenn. Propag. 51(3), 421 (2003)

[96] A. Kiourti,K. S. Nikita, A review of implantable patch antennas for biomedical telemetry: Challenges and solutions, IEEE Antennas Propag. Mag. 54(3), 210 (2012)

[97] N. Behdad and K. Sarabandi , Slot antenna miniaturization using distributed inductive loading, Proc. IEEE Antennas Propag. Soc. Int. Symp. 1, 308 (2003)

[98] M. Fallahpour and R. Zoughi , Antenna miniaturization techniques: A review of topology- and material-based methods, IEEE Antennas Propag. Mag. 60(1), 38 (2018)

[99] S. Thankachan and B. Paul , Dual band electrically small complementary double negative structure loaded metamaterial inspired circular microstrip patch antenna for WLAN applications, Appl. Sci. (Basel) 12(6), 3035 (2022)

[100] S. S. Al-Bawri , M. T. Islam , T. Shabbir , G. Muhammad , M. D. S. Islam , and H. Y. Wong , Hexagonal shaped near zero index (NZI) metamaterial based MIMO antenna for millimeter-wave application, IEEE Access 8, 181003 (2020)

[101] Y. Juan , W. Yang , and W. Che , Miniaturized low-profile circularly polarized metasurface antenna using capacitive loading, IEEE Trans. Antenn. Propag. 67(5), 3527 (2019)

[102] S. Xiao , T. Wang , T. Liu , X. Yan , Z. Li , and C. Xu , Active modulation of electromagnetically induced transparency analogue in terahertz hybrid metal-graphene metamaterials, Carbon 126, 271 (2018)

[103] D. R. Jackson , J. T. Williams , A. K. Bhattacharyya , R. L. Smith , S. J. Buchheit , and S. A. Long , Microstrip patch designs that do not excite surface waves, IEEE Trans. Antenn. Propag. 41(8), 1026 (1993)

[104] I. Papapolymerou , R. F. Drayton , and L. P. B. Katehi , Micromachined patch antennas, IEEE Trans. Antenn. Propag. 46(2), 275 (1998)

[105] J. G. Yook and L. P. B. Katehi , Micromachined microstrip patch antenna with controlled mutual coupling and surface waves, IEEE Trans. Antenn. Propag. 49, 1382 (2001)

[106] A. C. G. Gauthier and G. M. Rebeiz , Microstrip antennas on synthesized low dielectric-constant substrates, IEEE Trans. Antenn. Propag. 45(8), 1310 (1997)

[107] V. R. Komanduri,D. R. Jackson,J. T. Williams,A. R. Mehrotra, A general method for designing reduced surface wave microstrip antennas, IEEE Trans. Antenn. Propag. 61(6), 2887 (2013)

[108] S. A. Amanatiadis , T. D. Karamanos , and N. V. Kantartzis , Radiation efficiency enhancement of graphene THz antennas utilizing metamaterial substrates, IEEE Antennas Wirel. Propag. Lett. 16, 2054 (2017)

[109] R. Dhananjeyan , S. Ramesh , D. R. Kumar , and O. P. Kumar , Compact octagonal MIMO antenna system for broadband applications with enhanced isolation and wideband performance, Sci. Rep. 15(1), 18921 (2025)

[110] B. A. F. Esmail and S. Koziel , Design and optimization of metamaterial-based highly-isolated MIMO antenna with high gain and beam tilting ability for 5G millimeter wave applications, Sci. Rep. 14(1), 3203 (2024)

[111] D. Lin , P. Fan , E. Hasman , and M. L. Brongersma , Dielectric gradient metasurface optical elements, Science 345(6194), 298 (2014)

[112] G. Zheng , H. Mühlenbernd , M. Kenney , G. Li , T. Zentgraf , and S. Zhang , Metasurface holograms reaching 80% efficiency, Nat. Nanotechnol. 10(4), 308 (2015)

[113] A. V. Kildishev , A. Boltasseva , and V. M. Shalaev , Planar photonics with metasurfaces, Science 339(6125), 1232009 (2013)

[114] J. Hu,S. Bandyopadhyay,Y. Liu,L. Shao, A review on metasurface: From principle to smart metadevices, Front. Phys. (Lausanne) 8, 586087 (2021)

[115] X. Ni , N. K. Emani , A. V. Kildishev , A. Boltasseva , and V. M. Shalaev , Broadband light bending with plasmonic nanoantennas, Science 335(6067), 427 (2012)

[116] M. Lin,X. Huang,B. Deng,J. Zhang,D. Guan,D. Yu,Y. Qin, A high-efficiency reconfigurable element for dynamic metasurface antenna, IEEE Access 8, 87446 (2020)

[117] Z. Wang , S. Zhao , and Y. Dong , Pattern reconfigurable, low-profile, vertically polarized, ZOR-metasurface antenna for 5G application, IEEE Trans. Antenn. Propag. 70(8), 6581 (2022)

[118] X. Ren , H. Zhai , Y. Jia , M. Wang , and Y. Lei , Wideband RCS reduction for circular-polarized slot array antennas based on composite metasurface, IEEE Antennas Wirel. Propag. Lett. 23(12), 4867 (2024)

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