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This communication presents a millimeter-wave wideband dual-polarized low-temperature cofired ceramics (LTCC) antenna array based on metasurfaces (MSs) for beam-scanning applications. Benefiting from the wideband and large-freedom property of MS-based structures, a novel ±45° dual-polarized wideband MS-based antenna (MSA) element with high isolation is designed. The antenna element is fed by two orthogonal striplines on different layers, through a crosslike dog-bone slot and a narrow slot, respectively, to realize the two polarizations. The feeding structure consists of slot–stripline–slot–stripline from top to bottom and is specially designed to improve the polarization isolation of the antenna element. The proposed MSA element is compactly arranged with a small distance ($ < 0.5\lambda$) to construct a 4 $\times $ 4 array integrated in an LTCC package, where via walls with metal ring strips are loaded between adjacent elements to reduce the gain fluctuation. Consequently, the array can achieve a good beam-scanning capability over a wide band of 19.5% with a maximum scanning angle up to ±55° and a small gain variation of less than 3 dB. Meanwhile, the active $S$ parameters almost always remain below −10 dB, enabling good impedance matching when scanning at all angles. With these features, the proposed design has potential for application in 5G base-station systems. [ABSTRACT FROM AUTHOR]

A novel low-profile wideband dual-circularly polarized metasurface antenna based on a traveling-wave sequential feeding mechanism is proposed. It consists of 4 × 4 rectangle metasurface cells and is excited by a simple two-port traveling-wave feeding network, which includes four rotated Z-shaped slots etched on the ground and a ring feeding line, to provide stable sequential phases of 0°, 90°, 180°, 270° for realizing dual-circular polarizations. By changing the width of four Z-shaped slots, the equal amplitude of two orthogonal electric fields can be achieved and good right- and left-handed circular polarization (RHCP, LHCP) can be realized accordingly in a wideband. Moreover, a metasurface is utilized as a radiator to improve the impedance bandwidth (IMBW) as well as radiation performance. For demonstration, one prototype with an overall size of 0.88λ0 × 0.88λ0 × 0.06λ0 centered at 5.3 GHz is fabricated and measured. The measured results show that the proposed low-profile antenna realizes a large 10-dB IMBW of 38.4% (4.33–6.39 GHz) and 46.6% (6.17–6.70 GHz), 3-dB axial-ratio bandwidth of 38.4% and 39.3%, respectively, for RHCP and LHCP states. In addition, the polarization isolation is over 12 dB in the entire band of interest. [ABSTRACT FROM AUTHOR]

This article presents a novel broadband dual-polarized filtering patch antenna array using low-temperature cofired ceramic (LTCC) process for 5G millimeter-wave (mmW) applications. The filtering antenna element is implemented using a ± 45° polarized patch antenna fed by two pairs of differential L-type probes. An additional square ring and open strips are connected to each probe, resulting in radiation nulls and realizing the lower/upper stopband rejection level over 24 dB with skirt selectivity. The cross coupling among these structures not only introduces filtering responses, but also contributes to broadening the passband of 24.25–29.5 GHz covering 5G n257/n258/n261 bands. The antenna performance is validated by equivalent circuits based on transmission line models, which reveals clearly the principles of filtering antenna step by step and provides guidelines for further designs. The proposed filtering antenna element is expanded to a $4\times 4$ filtering antenna array with shunt-fed feeding networks. The spacing between elements is $0.48~\lambda _{0}$. The measured results demonstrate that the array performs good filtering characters including high stopband rejection, high selectivity, and wide upper stopband up to 40 GHz, where the antenna efficiency (considering radiations from all the directions) is less than 5%. In addition, the differential feeds provide symmetric radiation patterns with low cross-polarized counterparts. Compared with other reported works, the proposed filtering antenna/array has excellent performances of wideband, high stopband rejection and wide upper stopband for potential 5G mmW applications. [ABSTRACT FROM AUTHOR]

A novel method of dual-band dual-beam control (DDC) is proposed and applied in metasurface antennas (MSAs). Based on this DDC method, the feeding network employed in MSAs can realize independent forward and/or backward radiation of two bands. Combining the metasurface cells and feeding network, the desired bands and the corresponding beam angles of MSAs can be controlled. The symmetrical two-port feeding network consists of uniformly spaced slots in the ground and a bent microstrip line beneath the slots, so that two identical beams are realized. The radiation direction of the two bands can be implemented independently by adjusting the distance of the slots and length of the bent line simultaneously. To verify the design strategies, two prototypes (MSA A and MSA B) with different performance are designed, respectively. As a result, the proposed MSAs can achieve independent beam angels of two bands with low profile and compact design. The above good features make the proposed MSAs potential candidates in base-station antennas of high-capacity wireless communication system. [ABSTRACT FROM AUTHOR]