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A polarization‐insensitive frequency‐selective rasorber (FSR) with a high‐transmission passband and two wide absorption bands is proposed. The proposed FSR consists of an absorptive layer and a frequency selective surface (FSS) layer. The absorptive layer employs a four‐arm square spiral resonator with four fork shape resonators connected by lumped resistances to form broadband transmission and absorption. The FSS layer is formed by three metallic patches and two dielectric substrates, which are applied to generate a wide passband. The simulated results demonstrate that the 1‐dB transmission passband enables to obtain of 40.2% fractional bandwidth (FBW) from 9 GHz to 13.53 GHz, and the minimum in‐band insertion loss (IL) is 0.07 dB. Besides, the reflection bandwidth below −10 dB can reach 135% from 3.29 GHz to 16.90 GHz. Finally, the FSR's prototype is fabricated and measured. The results of measurement are fitted well with the simulated ones, which means that the proposed FSS can achieve broadband transmission and absorption. [ABSTRACT FROM AUTHOR]

A dual‐polarized wideband Fabry‐Perot (FP) antenna based on a wedge‐shaped phase correcting structure (WPCS) is proposed. The antenna adopts a wideband dual‐linear polarized slot‐coupled antenna as a primary antenna, and adopts a single‐layer FSS structure with positive reflection phase gradient characteristics as a partially reflecting surface (PRS) of the FP resonator, to optimally excite the FP cavity resonances within a wide operating band. Moreover, a small circular metal patch array is printed on the other side of the FSS unit structure. The small circular patch array effectively increases the reflection amplitude without changing the positive reflection phase gradient characteristics of the PRS, which improves the FP antenna gain. In addition, a highly graded WPCS is loaded in the resonant cavity to properly compensate the phase between different reflection paths inside the resonant cavity, which enhances the gain of the FP antenna in a wide band. Finally, the measured peak gains of the FP antenna under the excitation of Port 1 and Port 2 are 16.0 dBi and 15.89 dBi, respectively, and the gain enhancement can reach up to 3 dBi after loading the WPCS. The measured 10‐dB impedance‐matching operating bandwidth of dual‐polarized common coverage is 14.08 to 16.45 GHz (15.53%). [ABSTRACT FROM AUTHOR]

In this paper, an orbital angular momentum (OAM) metasurface antenna is proposed. Based on the idea of controlling the radiation and scattering simultaneously, the metasurface unit cells play two roles of radiating and scattering energy. For radiation, the metasurface unit cells are excited by two carefully designed phase shift networks (PSNs) at two orthogonal directions. Thus, OAM vortex waves with topological charge l = ±1 are generated at 7.48 GHz band. For scattering, the incident wave is deflected through the phase canceling scheme due to the anisotropy property of the metasurface unit cells. As a result, the in‐band radar cross section is reduced. A prototype of the antenna was fabricated and measured. The measurement results agreed well with the simulations. [ABSTRACT FROM AUTHOR]

A dual‐polarized substrate‐integrated hollow antenna (SIHA) and its cylindrically conformal phased array are proposed. The bandwidth of the proposed SIHA is 35%. The cylindrically conformal phased array with 24 SIHA subarrays can scan its beam in the whole horizontal plane and scan its beam within ± 60° in the vertical plane. The proposed array with wide band, wide‐angle scanning, and dual‐polarization characteristics is appropriate for millimeter‐wave base station applications. [ABSTRACT FROM AUTHOR]

This article presented a high selectivity and efficiency differential dual‐polarized filtering patch antenna. A square driven patch together with a square parasitic patch are utilized to obtain a filtering performance. By loading an upper parasitic patch with a cross slot in the center, a radiation null is introduced on the high side of the passband. Two pairs of slots with the same size of folded U‐shape are symmetrically etched on the diagonal of the driven patch, generating another radiation null on the low side of the passband. Thus, the antenna can achieve a good filtering gain response with two radiation nulls, realizing high selectivity. Additionally, as no extra filtering circuit is utilized, high radiation efficiency is also acquired. An antenna prototype is processed and measured, showing a bandwidth of 7.4%, high isolation of 32 dB, an antenna peak gain of 9 dBi and an efficiency of −0.29 dB in the center frequency. [ABSTRACT FROM AUTHOR]

Owing to the high cross‐polarization discrimination (XPD) and high isolation characteristics, differential excitation is often employed in dual‐polarized microstrip antennas. However, the number of excitation ports will be doubled, and the power dividers in the differential circuit will introduce additional loss, the differential excitation scheme is thus not suitable for dual‐polarized large‐scale MIMO antenna arrays. In this work, a novel dual‐polarized stacked microstrip antenna with trident‐shaped baluns is proposed for base station MIMO array development. The trident‐shaped balun is proposed to replace the traditional differential excitation structures, while keeping the merits of high XPD and high isolation. The proposed antenna operates in the frequency band of 3.3‐3.8 GHz. The profile height of the antenna is only 0.09λ0 (λ0 is the free‐space wavelength at the central frequency), which is much lower than traditional base station antennas (0.25λ0) in the sub‐6 GHz band. Moreover, a defective ground structure is implemented in a 2 × 2 MIMO antenna array to efficiently suppress the mutual coupling among antenna elements. Both simulated and measured results validate the design. Owing to its low‐profile height and low mutual coupling characteristic, the proposed design is a good candidate for sub‐6 GHz band base station MIMO array developments. [ABSTRACT FROM AUTHOR]

This article presents a compact broadband dual‐polarized antenna for use in the sub‐6 GHz 5G applications. The antenna is a novel magneto‐electric (ME) dipole with microstrip‐line aperture‐coupled feed, that is, it is composed of two orthogonal microstrip‐lines coupled with four shorted patches through a crossed slot for the broadband dual‐polarized radiation. The electric and magnetic dipole modes are formed by the shorted patches and the gap between the patches, respectively. Therefore, the antenna achieves a low‐profile. To reduce the back radiation at the aperture‐coupled feed and remain the low‐profile, the antenna is backed by a high impedance surface. The final design with an overall size of 50 mm × 50 mm × 12.5 mm (0.5λmin × 0.5λmin × 0.125λmin) has been fabricated and measured. The measurements result in a bandwidth of 33% (3.02‐4.02 GHz) for voltage standing wave ratio <1.5 and an isolation of >25 dB among the two ports. Its bandwidth covers the specific 5G NR n78 band (3.3‐3.8 GHz). In addition, the antenna achieved a broadside gain of 7.9‐8.5 dBi, a front‐to‐back ratio of >18 dB, and a cross‐polarization level of <− 20 dB across the operational bandwidth. [ABSTRACT FROM AUTHOR]

A broadband dual‐polarized end‐fire millimeter‐wave antenna array without ground clearance is proposed in this paper for 5G communication terminals. Horizontally polarized (HP) and vertically polarized (VP) radiation are realized using a quasi‐Yagi antenna and a substrate‐integrated waveguide cavity antenna, respectively. A multilayer dielectric plate for which the relative dielectric constant increases from top to bottom is used to achieve the HP antenna's end‐fire radiation without ground clearance. The VP antenna is implemented using the HP antenna, GND, and three rows of metallic vias. The HP and VP antennas are located in the same area, making the integrated design very compact. An inverted L‐shaped feeding structure was used to broaden the VP antenna's bandwidth with a low profile (0.12λL). Finally, a 4 × 1 array was processed to verify the proposed antenna. The measured results show that the overlapping bandwidth is 24 to 29.5 GHz (20.6%) for two polarization modes. The maximum gain varies between 7.6 to 9.1 and 6.5 to 9.1 dBi for the HP and VP modes, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a broadband dual‐polarized omnidirectional antenna with a simple feeding structure. It consists of a monopolar patch element for vertically linear polarization (VP) and a circular printed‐dipole array for horizontally linear polarization (HP). The monopolar patch antenna is loaded with shorting vias and coupled ring in order to broaden the VP bandwidth, nevertheless keeping a low profile. The printed dipoles with integrated balun are arranged on a circular substrate and incorporated with a 1‐to‐4 power divider for achieving the broadband HP omnidirectional radiation. One of the key features is to replace a shorting‐via in the monopolar patch by the coaxial line of the HP element, allowing a simple configuration and not affecting the VP radiation. The final design with a profile of 0.28λmin has been fabricated and measured. The measurements result in an overlapped impedance bandwidth of 25.4% (2.2‐2.84 GHz) and port‐to‐port isolation of >33 dB. Also, the antenna achieves the peak gain values of 8.0 and 5.6 dBi for the VP and HP radiations, respectively. [ABSTRACT FROM AUTHOR]

The contribution of this work is to propose a cavity-based antenna with both dual-polarization and bandpass filter characteristics. Proper cavity resonators and antenna based on the substrate integrated waveguide (SIW) technology are designed utilizing the low temperature co-fired ceramics (LTCC) for demonstration. By properly arranging and coupling the cavities, a shaping of filter-like response for the antenna gain and input return loss can be obtained. Measures for achieving a good isolation and a low cross-polarization level have also been taken into account during the design procedure. A 4th-order prototype working in the Ka-band is designed and fabricated. Investigations show that the antenna presents a good isolation below -29 dB across the operating bandwidth, together with a cross-polarization level lower than -25 dB at the center working frequency. The performance of the prototype has been verified in the measurement. [ABSTRACT FROM AUTHOR]

A wideband dual-polarized microstrip antenna is presented. By designing the coplanar parasitic patches and modified feed probes, antenna profile is decreased significantly. Shorted pins are used and 34 dB isolation between input ports is then achieved. A phase difference feed network is introduced to suppress higher-order modes and reduce the cross polarization to −27 dB. To verify the design, a prototype of the antenna is fabricated and experimentally studied. Measured results show that 30.3% operating bandwidth (VSWR < 1.5) and good dual linear polarization characteristics with a profile height as low as 0.08λ are achieved. Due to the very compact configuration, the proposed antenna is suitable for micro-base-station applications. [ABSTRACT FROM AUTHOR]

ABSTRACT A cavity-backed antenna with low-profile, dual-polarization, and wide operating bandwidth characteristics is proposed. In this design, two orthogonally positioned triangular bowtie antennas printed on a low-cost substrate are loaded onto a square cavity, so that two orthogonal linear polarizations can be excited. By further introducing four extended ground stubs from each side of the square cavity, the proposed antenna can also acquire low-profile characteristic of approximately 0.1λ (15 mm). To achieve good impedance matching, additional circular slots are introduced into each bowtie design. The measured results show that the proposed antenna can cover a wide operating bandwidth of 62% (2.0-3.8 GHz) with a VSWR of 2:1. Besides exhibiting good isolation (>20 dB) between the two feeding ports, desirable realized gains (6.0-10.5 dBi) over the wide operation band are also demonstrated. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:724-730, 2016. [ABSTRACT FROM AUTHOR]

In this paper, a novel broadband dual‐polarization patch antenna is proposed. Antisymmetric Γ feeding network is applied to excite the radiating patch etched on the upper side of the horizontal substrate, which could minimize the undesired radiation from the probe and extend the impedance bandwidth. For verifying the proposed approach, a prototype is fabricated and measured, the simulated and measured results show the antenna has a wide impedance bandwidth of 48% (1.66‐2.71 GHz) for S11 < −10 dB, as well as stable radiation gain around 9.5 dBi with low cross‐polarization. In addition, the total height of the antenna is only 0.17λ0 (λ0is the free space wavelength of central frequency) and high port‐to‐port isolation is better than 30 dB. The characteristics of the proposed antenna illustrate it can be an indication for a micro base station in the mobile communication system. [ABSTRACT FROM AUTHOR]