Search Results (361)

This paper presents a novel dual-band flexible antenna, uniquely designed and extended to array as well as MIMO configurations for the Sub-6 GHz band. The single-element monopole antenna features a modified rectangular radiator with two L-strips and a reduced ground plane, enabling a compact dual-band response. The proposed four-element, two-port MIMO configuration is extended from the 1 × 2 array antenna, achieving an overall dimension of 57 × 50 × 0.1 mm³, making it exceptionally compact and flexible compared to existing rigid and bulkier designs. Operating in the 3.6–3.8 GHz and 5.65–5.95 GHz bands, the antenna delivers a high gain of 5.2 dBi and 7.7 dBi, outperforming many designs in terms of gain while maintaining the superior isolation of >22 dB utilizing a defected ground structure (DGS). The design satisfies key MIMO diversity metrics (ECC < 0.05, DG > 9.99) and demonstrates low SAR values (0.0702/0.25 W/kg at 3.75 GHz and 0.175/0.507 W/kg at 5.9 GHz), making it highly suitable for wearable and on-body communication, unlike many rigid counterparts. Fabricated on a flexible polyimide substrate, the antenna addresses challenges such as size, bandwidth, isolation, and safety in MIMO antenna design. The performance, validated through fabrication and measurement, establishes the proposed antenna as a superior alternative to existing MIMO designs for compact, high-performance Sub-6 GHz 5G applications. Full article

A Ka-Band, 26.5–40 GHz, omnidirectional metamaterial-inspired antenna was designed, built, and tested to develop a simple printed compact (10.3 mm × 10.3 mm × 0.0787 mm) multiple-point sensor for air pollution monitoring. This Ka-band antenna generated a dual band at 27.49–29.74 GHz and 33.0–34.34 GHz. The VSWR values within the two bands are less than 1.5. The radiation and total efficiency are 97% and 92% in the first band and they are both 96% in the second band. The maximum gain is between 3.26 and 5.50 dBi and between 5.09 and 6.52 dBi in the first and second bands, respectively. The dual band is the key to enhancing the sensor’s detection accuracy. This Omni MTM-inspired antenna/sensor can effectively detect toxic and neurotoxic metal particles, i.e., lead, zinc, copper, and nickel, in evidently polluted living environments, such as factory/industrial environments, with different particle/mass concentrations. This sensor can be adapted to detect metal pollutants in different environments, such as water or other fluid-based matrices, and can also be applied to long-range communication repeaters and 5G harvesting energy devices, to name a few. Full article

This paper proposes a dual-band antenna to support 5G communication with linear polarization and the global navigation satellite system (GNSS) band with circular polarization. A single inverted T-shaped patch antenna with a defective ground was designed on the Schott Foturan II (Ceramized 560 degrees) substrate. Then, an L-shaped stub and slot were inserted into the ground to achieve the 5G and GNSS bands. The antenna was then designed as a 1 × 2 multiple-input and multiple-output (MIMO) antenna to increase the directivity. A square ring-shaped frequency selective surface (FSS) was intended on the FR-4 substrate to improve the gain of the MIMO antenna. The FSS MIMO antenna increased the 3D gain from 2.8 to 5.4 dBi for the GNSS band and from 4.9 to 6.43 dBi for the 5G n79 band. The proposed antenna can receive and transmit the frequency bands covering sub-6 GHz 5G band n79 (4400–5000 MHz) and GNSS band E6 (1260–1300 MHz), respectively. A multi-port unmanned aerial vehicle antenna was fabricated, and its performance was characterized in terms of bandwidth, axial ratio, and gain. Full article

This paper presents a novel approach to synthesizing phased antenna arrays (PAAs) by combining Taylor-series expansion with neural networks (NNs), enhancing the PAA synthesis process for modern communication and radar systems. Synthesizing PAAs is crucial for these systems, offering versatile beamforming capabilities. Traditional methods often rely on complex analytical formulations or numerical optimizations, leading to suboptimal solutions or high computational costs. The proposed method uses Taylor-series expansion to derive analytical expressions for PAA radiation patterns and beamforming characteristics, simplifying the optimization process. Additionally, neural networks are employed to model the intricate relationships between PAA parameters and desired performance metrics, providing adaptive learning and real-time adjustments. A validation of the proposed method is performed on a dual-band 5G antenna, which exhibits marked resonances at 28.14 GHz and 37.88 GHz, with reflection coefficients of $S_{11}$ = −19 dB and $S_{11}$ = −19.33 dB, respectively. The integration of Taylor expansion with NNs offers improved efficiency, reduced computational complexity, and the ability to explore a broader design space. Simulation results and case studies demonstrate the effectiveness and applicability of the approach in practical scenarios. This work represents a significant advancement in PAA synthesis, showcasing the synergistic integration of mathematical modeling and artificial intelligence for optimized antenna design in modern communication and radar systems. Full article

With the rapid development of Wi-Fi 6/6E and dual-band wireless systems, there is an increasing demand for compact antennas with balanced high-gain performance across both 2.4 GHz and 5 GHz bands. However, most existing dual-band metasurface antennas face challenges in uneven gain distribution between lower/higher-frequency bands and structural miniaturization. This paper proposes a high-gain dual-band metasurface antenna based on an artificial magnetic conductor (AMC) array, which has a significant advantage in miniaturization and improving antenna performance. Two types of dual-band AMC structures are applied to design the metasurface antenna. The optimal antenna with dual-slot AMC array operates in the 2.42–2.48 GHz and 5.16–5.53 GHz frequency bands, with a 25% size reduction compared to the reference dual-band U-slot antenna. Meanwhile, high gains of 7.65 dBi and 8 dBi are achieved at 2.4 GHz and 5 GHz frequency bands, respectively. Experimental results verify stable radiation gains across the operation bands, where the total efficiency remains above 90%, agreeing well with the simulation results. This research provides an effective strategy for high-gain and dual-band metasurface antennas, offering a promising solution for integrated modern wireless systems such as Wi-Fi 6, Bluetooth, and MIMO technology. Full article

This paper presents a novel design of a compact dual-band dual-mode wearable antenna. The antenna is fed through a single coaxial feed probe, which excites TM₀₁ and TM₁₁ modes at 2.45 GHz and 5.8 GHz, respectively. These modes exhibit distinct radiation characteristics. The omnidirectional TM₀₁ mode at 2.45 GHz is suitable for on-body communication, while the directional TM₁₁ mode at 5.8 GHz is more appropriate for off-body communication. The antenna prototype was fabricated and measured. The measured performance is consistent with the simulations. Additionally, further simulations and measurements were conducted to verify the interactions between the proposed antenna and the human body. The results demonstrate that the proposed antenna exhibits significant potential as a candidate for wireless body area network (WBAN) communications. Full article

To address the inherent contradiction between low-profile design and high gain in traditional omnidirectional antennas, as well as the narrow bandwidth constraints of ENZ antennas, this study presents a dual-mode ENZ-FP collaborative resonant antenna array design utilizing a substrate-integrated waveguide (SIW). Through systematic analysis of ENZ media’s quasi-static field distribution, we innovatively integrated it with Fabry–Perot (F–P) resonance, achieving unprecedented dual-band omnidirectional radiation at 5.18 GHz and 5.72 GHz within a single ENZ antenna configuration for the first time. The directivity of both frequencies reached 12.0 dBi, with a remarkably low profile of only 0.018λ. We then extended this design to an ENZ-FP dual-mode beam-scanning array. By incorporating phase control technology, we achieved wide-angle scanning despite low-profile constraints. The measured 3 dB beam coverage angles at the dual frequencies were ±63° and ±65°, respectively. Moreover, by loading the impedance matching network, the −10 dB impedance bandwidth of the antenna array was further extended to 2.4% and 2.7%, respectively, thus overcoming the narrowband limitations of the ENZ antenna and enhancing practical applicability. The antennas were manufactured using PCB (Printed Circuit Board) technology, offering high integration and cost efficiency. This provides a new paradigm for UAV (Unmanned Aerial Vehicle) communication and radar detection systems featuring multi-band operation, a low-profile design, and flexible beam control capabilities. Full article

A circularly polarized (CP) textile antenna is investigated for concurrent on- and off-body wireless communications in the 2.38 GHz medical body area network and 5.8 GHz industrial, scientific, and medical bands in the wireless body area network. The proposed scheme consists of a square microstrip patch antenna (MPA), in which four shorting pins are employed to tune the two resonate modes of TM₁₀ and TM₀₀. Notably, the slant corners on MPA are cut symmetrically to realize unidirectional CP radiation, enabling off-body communication. Moreover, four rotating L-shaped parasite elements are loaded to excite the horizontal polarization mode (TM_hp), which is combined with the TM₀₀ mode to implement CP omnidirectional radiation along the human body. For verification, a proof-of-concept prototype with the dimensions of 45 mm × 45 mm × 2 mm was fabricated and characterized. The measured −10 dB impedance bandwidths of 2.5% and 6.7%, the 3 dB AR bandwidths of 2.5% and 2.7%, and the maximum realized gains of −2.8 and 6.8 dBic are achieved in dual bands, respectively. The experimental tests, such as human body loading, structural deformation, and humidity variation, were carried out. In addition, the wireless communication capability was measured and the radiation safety is evaluated. These performances show that the proposed antenna is an appropriate choice for multifunctional wearable applications. Full article

Millimeter-wave signals experience substantial path loss when penetrating common building materials, hindering seamless indoor coverage from outdoor networks. To address this limitation, we present the 28-GHz “Meta-Window”, a mass-producible, visible transparent device designed to enhance millimeter-wave signal focusing. Fabricated via metal sputtering and etching on a standard soda-lime glass substrate, the meta-window incorporates subwavelength metallic structures arranged in a rotating pattern based on the Pancharatnam–Berry phase principle, enabling 0–360$°$ phase control within the 25–32 GHz frequency band. A 210 mm × 210 mm prototype operating at 28 GHz was constructed using a 69 × 69 array of metasurface unit cells, leveraging planar electromagnetic lens principles. Experimental results demonstrate that the meta-window achieves greater than 20 dB signal focusing gain between 26 and 30 GHz, consistent with full-wave electromagnetic simulations, while maintaining up to 74.93% visible transmittance. This dual transparency—for both visible light and millimeter-wave frequencies—was further validated by a communication prototype system exhibiting a greater than 20 dB signal-to-noise ratio improvement and successful demodulation of a 64-QAM single-carrier signal (1 GHz bandwidth, 28 GHz) with an error vector magnitude of 4.11%. Moreover, cascading the meta-window with a reconfigurable reflecting metasurface antenna array facilitates large-angle beam steering; stable demodulation (error vector magnitude within 6.32%) was achieved within a ±40$°$ range using the same signal parameters. Compared to conventional transmissive metasurfaces, this approach leverages established glass manufacturing techniques and offers potential for direct building integration, providing a promising solution for improving millimeter-wave indoor penetration and coverage. Full article

In this study, a dual-band dual-beam shared-aperture reflector antenna based on a Cassegrain configuration is designed using a frequency-selective surface (FSS) subreflector. The antenna generates two shaped beams that operate at different frequencies and can spatially overlap. One beam contour can be independently optimized by properly designing the shape of the main reflector. The contour of the second beam is defined by optimizing the unit cell and geometry of the FSS-based subreflector once the shape of the main reflector is set. The reflector antenna design is cast as the optimization of a suitably defined cost function aimed at yielding the desired directivity performance in the regions of coverage. In order to validate the proposed solution, a set of numerical experiments was conducted using most of China and Shaanxi province as benchmark examples. Full article

To achieve multi-band coverage within limited space, reduce antenna types, and enhance communication capabilities, an eight-unit dual-band 5G MIMO antenna array is proposed based on a monopole structure. The antenna operates in two frequency bands (3.23–4.14 GHz and 4.31–5.3 GHz), covering the n78 and n79 bands for 5G applications. The dual-band and miniaturized design of the antenna elements is achieved through the slotting and branch-loading techniques. The orthogonal placement of corner antenna elements is implemented to reduce coupling and optimize spatial utilization, achieving isolation of over 16 dB between elements. The introduction of a metasurface structure further improved isolation by 2 dB and increased the peak gain of the antenna array to 11.95 dBi. A prototype is fabricated and tested, demonstrating the following performance metrics: isolation exceeding 18 dB, gain ranging from 6 to 12 dBi, envelope correlation coefficient below 0.05, channel capacity greater than 41 bps/Hz, diversity gain of approximately 10 dB, total active reflection coefficient below −24 dB, and radiation efficiency exceeding 72%. These results confirm the superior performance of the proposed antenna design. Full article

This paper presents the design of a dual-band filter and a diplexer using an extremely miniaturized substrate-integrated coaxial cavity (SICC) structure. The presented dual-band filter can function as a front-end circuit block connected to 5G antennae, enabling dual-passband operation for 5G applications. The diplexer is designed for use in 5G communication systems, positioned after the 5G antennae to facilitate the switching of transmitting (Tx) and receiving (Rx) signals between the Tx and Rx terminals. The main contribution of this work is the development of a highly miniaturized substrate-integrated coaxial cavity (SICC) to design a dual-band filter (DBF) and a diplexer. The circuit area of the proposed dual-frequency SICC is a mere 2.1% of its conventional substrate-integrated waveguide (SIW) cavity counterpart when operating at the same frequency. A dual-band filter and a diplexer are realized using two and three highly miniaturized SICC resonators, respectively. The dual-band filter is designed to have a transmission zero on each passband side to enhance signal selectively. At most in-band frequencies, the isolation between the diplexer’s channel bands exceeds 20 dB. A sample dual-band filter and diplexer have been fabricated for experimental validation, demonstrating excellent agreement between the measured and simulated data. To the best of the authors’ knowledge, the designed dual-band filter and diplexer achieve the highest circuit area efficiency within the categories of dual-band SIW cavity filters and diplexers. Full article

A low profile dual polarized transmitarray antenna, made of three identical layers, is proposed in this paper for Ku-band applications. The transmitarray comprises 22 × 22 symmetrical unit cells. A 3-bit phase compensation layer with less than α_T = 1.3 dB transmission loss and 2π transmission phase coverage for both linear polarized components at the central frequency f₀ = 12 GHz is designed. Moreover, for an incidence angle θ = 30°, the unit cell transmission loss is less than 2 dB; the transmission phase is close to the transmission phase at zero incidence angle θ = 0°. The fabricated transmitarray exhibits a measured peak gain of Gm₀ = 21 dB at the frequency f₀ = 12 GHz. The corresponding measured 1 dB gain bandwidth is BWg = 10.8% (11.1–12.4 GHz). The measured peak side lobe levels are SLL₀ = −20.8 dB at f₀ = 12 GHz. The transmitarray antenna can be used for beam steering up to an angle of γ_max = ±30° with a measured scan loss △G_MSL1 = 2.73 dB at f₁ = 12.4 GHz. Full article

Radio frequency identification (RFID) technology has gained significant attention in various industry sectors due to its potential for efficient inventory management, asset tracking, and object localization. Different RFID technologies are available; resorting to harmonic signals is currently less used but, recently, has gained interest in research activity. In this study, we present the design, prototype realization, and performance evaluation of a dual-band dual-polarized harmonic tag. The tag incorporates a dual-band matching circuit utilizing a zero-bias Schottky diode HSMS-2850 connected to a perturbed annular ring patch antenna. The antenna, in fact, is able to radiate in cross-polarization at the higher frequency. Through a comprehensive design methodology, including simulation optimization and prototype fabrication, we demonstrate the successful implementation of the tag. Measurements to validate the impedance matching properties, radiation patterns, and backscattering capability of the tag are also shown. Full article

The Finite Difference Time-Domain (FDTD) method is a powerful tool for electromagnetic field analysis. In this work, we develop a variation of the algorithm to accurately calculate antenna, microwave circuit, and target scattering problems. To improve efficiency, a single-field (SF) FDTD method is proposed as a numerical solution to the time-domain Helmholtz equations. New formulas incorporating resistors and voltage sources are derived for the SF-FDTD algorithm, including hybrid implicit–explicit and weakly conditionally stable SF-FDTD methods. The correctness of these formulas is verified through numerical simulations of a newly designed dual-band wearable antenna with an artificial magnetic conductor (AMC) structure. A novel antenna fed by a coplanar waveguide with a compact size of 15.6 × 20 mm² has been obtained after being optimized through an artificial intelligent method. A double-layer, dual-frequency AMC structure is designed to improve the isolation between the antenna and the human body. The simulation and experiment results with different bending degrees show that the antenna with the AMC structure can cover two frequency bands, 2.4 GHz–2.48 GHz and 5.725 GHz–5.875 GHz. The gain at 2.45 GHz and 5.8 GHz reaches 5.3 dBi and 8.9 dBi, respectively. The specific absorption rate has been reduced to the international standard range. In particular, this proposed SF-FDTD method can be extended to analyze other electromagnetic problems with fine details in one or two directions. Full article