This letter presents a wideband, high-gain, and low-profile dual-layer metasurface (MTS) circularly polarized antenna array for millimeter-wave applications. A modal-split synergistic frequency tuning strategy guided by characteristic mode analysis is proposed: By achieving controlled separation of orthogonal modes via H-shaped slots and utilizing the dual-layer MTS structure for synergistic tuning to broaden the modal bandwidth, this strategy fundamentally realizes the synchronized expansion of impedance and axial ratio (AR) bandwidths. In addition, a novel dual-layer LC decoupling resonator network is introduced to efficiently suppress array mutual coupling by generating antiphase compensating magnetic fields. Measured results of a 4 & times; 4 array prototype indicate that, with an ultralow profile of only 0.13$\lambda _{0}$, it achieves an impedance bandwidth of 39.20%, an AR bandwidth of 38.75%, and a peak gain of 20.45 dBic.

This paper proposes a Ka-band broadband circularly polarized (CP) antenna array with high cross-polarization discrimination (XPD). The design employs a four-layer stacked dielectric substrate structure, utilizing a 2 × 2 sequentially rotated (SR) array of substrate integrated cavity (SIC) magnetoelectric dipole elements as the core radiator. A double-layer substrate integrated waveguide (SIW) SR feeding network achieves precise 90 ^∘ phase delay at the center frequency, enabling the array to attain 30.33

This paper presents a low-profile Ku/Ka dual-band shared-aperture phased array antenna (SAPAA) that addresses conventional limitations in profile height, port isolation, and scanning angles through a hybrid-decoupling approach combining array decoupling surfaces (ADS) with defected ground structure (DGS), complemented by structural reuse techniques. The Ka-band elements utilize co-designed array decoupling surface layers integrated with DGS to effectively suppress surface current coupling, achieving wide-angle scanning capability of $$\pm 45^\circ$$ across the 32–36 GHz frequency band. For the dual-polarized Ku-band elements, feed matching is optimized through cross-shaped slots employing DGS structural reuse, demonstrating orthogonal port isolation exceeding 31 dB within the 14–18 GHz operational band while extending the scanning range to $$\pm 55^\circ$$ in both E- and H-planes. The antenna features an ultra-thin profile of merely 2.35 mm (0.28 $$\lambda _h$$ ), with measured inter-band isolation reaching 35 dB in the Ku-band and 18 dB in the Ka-band. Experimental verification confirms the design’s high performance and practical utility, offering a compact solution for multi-band integrated communication systems.

AbstractThis paper presents a novel millimetre‐wave (mmWave) 2D wide‐angle scanning (WAS) phased array antenna (PAA) based on decoupling surface (DS). The proposed element is a coaxial feeding stacked patch antenna structure that consists of an L‐shape coaxial probe, substrate integrated waveguide cavity, slot layer, radiating patch, DS and defective ground structure. The simulated impedance bandwidth for the element is 14.85% (26.18–30.34 GHz). The simulated result of the 2 × 2 array shows that the designed antenna based on DS achieves an isolation of ≥19 dB within the bandwidth. To validate the scanning capabilities of the proposed antenna, an 8 × 8 PAA prototype is fabricated and measured. The measured scanning range of the prototype achieves a 2D WAS range of ±56° at 27 GHz. The proposed antenna shows great potential in application scenarios, such as automotive radar and satellite communication due to its compact design and ability to achieve WAS in two dimensions.

A novel folded reflectarray and transmitarray antenna (FRTA), featuring a long distance, no diffraction, high mode purity, and low profile, is proposed to generate high-order Bessel beams carrying orbital angular momentum (OAM). First, two meta-atoms are designed for a full 2π phase coverage and amplitude variation from 0 to 1. Second, metasurfaces are constructed to adjust amplitude and phase independently, with a horn antenna integrated with the upper metasurface as a feeding source. Finally, the FRTA is simulated, fabricated, and measured to verify its generation efficiency of high-order Bessel OAM beams. The full-wave measurement results coincide well with the simulation results and theoretical derivation. The generated beam is more parallel and has a longer non-diffractive distance than conventional Bessel beams. In addition, mode l = 2, 3, 4 achieves approximately 80% mode purity, and more than 65% mode purity is achieved within 12–15 GHz, covering the 21.4% OAM bandwidth. Our study holds promise for applications in radar detection, beam forming, and wireless communications.

To realize the wide-angle beam-scanning characteristics of the dual-polarized base station antenna array, antenna elements are required to have a wide-beam property, and element spacing should be small. In this case, the strong mutual coupling between closely adjacent elements becomes the most critical issue. In this study, a combination of the multifunctional decoupling parasitic structure (MDPS) and the crown-type decoupling parasitic structure (CDPS) was introduced to the dual-polarized crossed-dipole antenna array to improve isolation between two adjacent elements. MDPS is critical for miniaturizing of the antenna unit, broadening its beamwidth, and decoupling between adjacent cross-polarized elements. The CDPS decouples adjacent co-polarized elements. The parasitic structure can be directly integrated into the antenna without introducing other structures between antenna units. Crucially, the proposed decoupling method does not degrade the beam-scanning capability of the antenna array. In this study, 1x 4 and 6x4 antenna arrays were designed, fabricated, and measured. The measured results revealed that the proposed antenna arrays can cover the 3.3-3.6-GHz 5G mobile service frequency band and exhibit an isolation greater than 20 dB between all adjacent units as well as a scanning angle of +/- 55 degrees.

Based on the all-metal structure of the crossed dipole antenna, the base station antenna with heat dissipation function is realized by introducing metal PIN structures of different heights between the radiator and the ground, on the radiator, and in the hollow part inside the radiator. Through the distribution of current on the surface of the antenna, the working principle of the antenna and the influence of the heat dissipation PIN structure on the radiation characteristics of the antenna are analyzed. The measurement results of the 3 × 3 antenna array show that the operating frequency band with voltage standing wave ratio (VSWR) less than 1.5 is 3.1–4.0 GHz. The gains of the central and edge elements in the array are greater than 5.6 dBi and 6.9 dBi, respectively. The front-to-back ratio is greater than 19 dB, the axial cross-polarization discrimination (XPD) is greater than 15 dB, and the XPD within the range of ±30° is greater than 10 dB. The thermal simulation results show that the maximum temperature of the proposed antenna array is lower than that of the microstrip antenna array and traditional dual-polarized dipole antenna array under the conditions of heat source power of 3.3 W, 14.1 W, and 18.8 W. The temperature differences between the proposed antenna and the microstrip antenna array are 18.6 °C, 76.2 °C, and 98.9 °C, while the temperature differences between the proposed antenna and the traditional dipole antenna array are 8.9 °C, 38.2 °C, and 50.9 °C. Under the above three power conditions, the difference between the maximum and minimum temperatures of the microstrip antenna array is 25.2 °C, 104.5 °C, and 136.8 °C, and the temperature difference of the traditional dipole antenna array is within 7 °C, while the proposed array is within 6.2 °C. All of this indicates that the proposed antenna array has strong thermal conductivity and heat dissipation performance.

A pair of semi-enclosed parallel-plate cavities are tilted at 45° and placed orthogonally to each other to form the dual-polarized antenna unit, which is fed by probe excitation. The simulation results show that the voltage standing wave ratio (VSWR) of the antenna is less than 1.5 in the 3.4-3.8 GHz frequency band, and the isolation between the two ports is greater than 21 dB. At the center frequency, the half-power beamwidth (HPBW) in the XOZ plane and YOZ plane are 108° and 107°, respectively.

The FSR with wide transmission band is realized by introducing a resistance layer above the bandpass FSS. The resistance layer is designed on the upper surface of the dielectric substrate and consists of a resistance film with a square structure, which provides the absorbing properties at high-frequency band. The bandpass FSS layer is designed on the upper and lower surfaces of the dielectric substrate, and four metal vias are introduced to connect the top and bottom structures together, providing good transmission properties at the low-frequency band. The designed FSR can provide a wide −3 dB bandwidth of 101% in the 1.73~5.25 GHz, and the −10 dB absorbing properties is achieved in the 8.31~12.14 GHz. Meanwhile, the structural dimension of the unit is about 0.03$\lambda \times 0.03\lambda$ ($\lambda$ being the central frequency of the transmission band) so that the good angular stability is obtained.

A dual-band shared-aperture antenna for both C-band (3.3-3.6GHz) and millimeter-wave band (24.25-29.5GHz) with a stacked and distributed 3D configuration is proposed in this communication. The C-band antenna is a dual-polarized microstrip antenna with a parasitic structure, and the millimeter-wave antenna is a $4 \times 4$ array of dipoles placed on the C-band antenna radiator. The C-band radiator also serves as the millimeter-wave ground plane, achieving structural reuse. The maximum gain of the C-band antenna is over 7dB, and the isolation between ports is over 45dB. The millimeter-wave antenna is linearly polarized, and the isolation between ports can reach over 20dB, allowing for beam scanning characteristics of ±55°.

A wideband compact printed dipole antenna array with an element size of 0.16 λ0 × 0.34 λ0 is proposed for millimeter-wave (mmW) applications, particularly for 5G applications. The two patches of the dipole are printed on two different layers to achieve a wide bandwidth of 50% (24–40 GHz) for SWR <2. Ground-signal-ground transmission line construction with a height difference between the feeding via and the two shorting vias is employed to achieve a relatively symmetrical radiation pattern. An antenna array consisting of the proposed antenna and a 1 to 8 substrate-integrated coaxial line feeding network is fabricated and measured. Simulations are also used to verify the beam scanning performance (up to ±50°). The proposed compact printed dipole antenna is a good contender for 5G mmW applications due to its wide band, compact size, and good beam scanning performance.

By introducing an equiangular spiral structure at the starting end of the Archimedes spiral, the input impedance of the antenna is reduced and the working bandwidth of the antenna is widened. Simultaneously, a curved spiral structure similar to a cosine wave is used to further reduce the dimensions of the antenna. The presented planar spiral antenna has a diameter of 94mm with a balun height of 18mm. In 1.2-12GHz the voltage standing wave ratio (VSWR) $\lt 2.$ And the axial ratio (AR) $\lt 3$ dB in 1.21-9.5GHz, and the peak gain range of right-handed circular polarization is between 2.5 and 4.9dB.

A low specific absorption rate (SAR) and high on-body efficiency tri-band smartwatch antenna is designed utilizing the theory of characteristic modes (TCM) of composite perfect electric conductors and lossy dielectric structures. The antenna works in the GPS frequency band, WLAN 2.4 GHz/Bluetooth frequency band, and 5G frequency band. After analyzing the characteristic modes of the antenna and human body in the above three frequency bands, the characteristic modes with small modal coupling coefficients (MCCs) are selected and excited. Due to the small mutual coupling between the antenna and the human body, the proposed antenna has good performance on both SAR and on-body efficiency. Its measured 10 g average body SAR is lower than 1.3 W/kg. When it is placed 0 mm above the body, its on-body efficiency is 9.3%–9.88% in the GPS frequency band, 12%–14.2% in the WLAN 2.4 GHz/Bluetooth frequency band, and 17.3%–20.1% in the 5G frequency band.

ABSTRACTAn inverted L-shaped antenna pair that can be applied to zero-ground-clearance mobile terminal equipment is presented. One inverted L-shaped antenna was placed on the frame of a mobile terminal and the other on the ground near the frame. The two antennas were placed in parallel, 4 mm apart, and a neutralisation line was introduced between them to achieve decoupling. The neutralisation line was integrated with an inverted L-shaped antenna introduced above the ground, which did not occupy any other installation space. The installation space occupied by the antenna pair was 17 × 8 × 6.2 mm3 (0.2 × 0.09 × 0.07 λ3). The measured results show that the − 6 dB impedance bandwidth of the antenna is 3.29–3.64 GHz, the isolation in the 3.3–3.6 GHz band is greater than 19.5 dB, the envelope correlation coefficient (ECC) is less than 0.3, and the antenna efficiency is 77.6–99.8%.KEYWORDS: Antenna pairMIMOmobile terminalneutralisation linezero ground clearance Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was supported in part by the National Natural Science Foundation of China (No. 61971335, No. 61401336).

In order to improve the heat dissipation capability of the 5G base station, the electromagnetic and thermal performances of a base station antenna array are co-designed by adopting all-metal electromagnetic band-gap (EBG) structures. The geometrical dimension of the EBG structure is determined through balancing the electromagnetic and thermal performances of the antenna array. The operating frequency band (voltage standing wave ratio (VSWR) $< $ 1.5) of the proposed antenna array can cover 3.4–3.8 GHz. Its realized gains, isolation, cross-polarized discrimination ratio, and half-power beamwidth are satisfactory compared with other state-of-the-art base station antennas. Most importantly, more than 9 $^{\circ }\mathrm{C}$ temperature reduction can be observed when comparing the heat dissipation capability of the proposed antenna array with the reference antenna array.

A compact 4-port antenna suitable for 5G band (3.4-3.6 GHz) is proposed. The antenna radiator consists of three open square ring structures with branches. Four antenna ports are introduced in an appropriate position of the radiator, and three decoupling inductors are introduced to realize decoupling between the ports. Based on the designed 4-port antenna as the unit, an 8 × 8 MIMO array is formed. The simulation results show that in the 3.4 – 3.6 GHz frequency band, the isolation of all ports is greater than 10.3 dB, the envelope correlation coefficient is less than 0.35, and antenna radiation efficiency is better than 45 %.

Radiation efficiency is one of the key parameters for smartphone antennas. However, the actual mechanism governing radiation efficiency remains unclear, and a few works have been published. This work is an attempt to extend the theory of characteristic modes (TCMs) to the lossy smartphone antenna for gaining insight into what causes efficiency variation and realizing efficiency improvement. Compared with the classical TCM, the CM analysis (CMA) adopted in this work has the capacity to handle lossy smartphone antenna. By using such an analysis approach, we find, quite interestingly, that suppressing the higher-order modes is an effective optimization strategy to enhance efficiency. Then, an optimized antenna with considerable improvement in efficiency is proposed. Finally, to meet the requirement of practical application, the additional LC circuit and through holes are introduced into this proposed optimized antenna. GSM 900 of 890–960MHz can be covered by this finally proposed antenna, and the measured peak total efficiency is improved from 26% to 43%. Due to the attractive features of small heights (4 mm) and tiny clearances (0.25 mm), the proposed designs are promising for application in a smartphone with a full-view display and thin profile.

In this paper, a three-band low specific absorption rate(SAR) smart watch antenna is designed. Firstly, the characteristic modes of the composite structure of the antenna and the lossy dielectric are calculated, and the low-SAR characteristics of the antenna are realized by exciting the low-coupling mode of the antenna in the Bluetooth band and the 3.5 GHz band. The -6dB bandwidth of the antenna can effectively cover 1565MHz-1585MHz, 2400MHz-2485MHz and 3400GHz-3600GHz. The total efficiency of the antenna in free space in all three frequency bands is greater than 80%. The 10g Body SAR of the antenna at 2440MHz is 1.05W/Kg, and the 10g Body SAR at 3500MHz is 1.3W/Kg.

A novel dual-polarized base station antenna for 5G applications is proposed in this paper. The antenna consists of a parallel plate waveguide and a dipole antenna, which are fed by an L-probe. To achieve a slant 45° dual-polarization, A dipole antenna is placed above the waveguide, and these are excited simultaneously. Arrange the waveguide periodically and exchange the directions of the dipole arms to form a ±45° dual-polarized antenna element. The simulation results show that the antenna has a good input impedance in the bandwidth of 3.39– 3.84 GHz and has high port-to-port isolation (>23dB). The antenna can be used as a heatsink antenna since it has an all-metal structure and the parallel plate can be utilized as a heatsink structure. Therefore, this antenna can be a promising contender for 5G services in a modern mobile communication system.

For a compact base station antenna array, the isolation between two co‐polarized adjacent elements and two cross‐polarized adjacent elements is relatively poor. The introduction of the array decoupled surface (ADS) on the top of the antenna and the introduction of parasitic structures between adjacent elements effectively improve the isolation of the co‐polarized and cross‐polarized adjacent elements. Array decoupled surface mainly suppresses the mutual coupling between the co‐polarized adjacent elements, and the parasitic structure mainly suppresses the mutual coupling between the cross‐polarized adjacent elements. Both simulated and measured results show that in the 3.3–3.6 GHz band, the return loss of all ports is better than 10 dB. By introducing the ADS and the parasitic patch structure, the isolation between two co‐polarized adjacent elements is improved from about 15 to 21.9 dB, and the isolation between two cross‐polarized adjacent elements is improved from about 13 to 22.4 dB. The isolation between two cross‐polarized elements in the same unit is greater than 27 dB.