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A novel design concept of multiple‐input and multiple‐output (MIMO) antenna with aiming to improve matching and port isolation at the same time is proposed. As the only additional component, a cross resonator is connected between the two patch antennas. The equivalent circuit model and calculation formula of resonant frequency of cross resonator in differential mode (DM) and common mode (CM) state are given, respectively. The same resonant frequency in the two states is the goal to want, and which is proved to be achievable by the relevant expression. Then, the two port antenna system can obtain good matching and high isolation. The coincidence between simulation and measured results brings the possibility of practical implementation. [ABSTRACT FROM AUTHOR]

In this article, a wideband base station antenna is designed. A new resonant mode is introduced into the antenna. Finally, four U‐shaped slots are added to the dipole of the antenna, and the antenna's third resonant mode is close to the first two resonant modes, which makes the antenna achieve wideband performance. The antenna is fabricated, and its performance is measured. The results show that the antenna has stable gain and radiation patterns. At the same time, the antenna works at 1.6–3.85 GHz with an impedance matching of −14 dB, and the relative bandwidth is 82%, the polarization isolation of the proposed antenna is better than −40 dB. [ABSTRACT FROM AUTHOR]

A novel concept of simultaneous matching, decoupling and miniaturization in multiple input multiple output (MIMO) antenna is proposed. Firstly, the integration of matching and decoupling can be achieved by making the resonant frequency of common mode (CM) and differential mode (DM) consistent. Then, the same resonant frequency of CM and DM will move to lower frequency through changing parameters value of the folded cross resonator. The MIMO antenna will operate normally at lower frequency with low mutual coupling without increase the volume. The operating frequency of antenna is reduced from 3 to 2.5 GHz of achieving 16.7% miniaturization, and the isolation is increased from 20 to 45 dB at 2.5 GHz at the same time. The measurement and simulation results are in good agreement, which verifies the correctness of the design. The goal of matching, decoupling and miniaturization for MIMO antenna will be completed without too much software optimization and other complex structures. [ABSTRACT FROM AUTHOR]

In this article, a simple dual wideband antenna with a novel feeding structure is designed based on two folded dipoles. Because of the particular antenna structure, the feeding structure of the antenna works as an impedance transformer. Then, four resonance modes are excited to achieve dual wideband performance, which brings a wide impedance bandwidth to the two pairs of dipoles. A prototype of the proposed antenna is fabricated and measured. Results show that the proposed antenna successfully supports the dual wideband operation of 1.4–2.7 GHz (63%) and 3.4–5.2 GHz (41%). [ABSTRACT FROM AUTHOR]

In this article, the realization method and operation mechanism of suppressing cross‐band scattering is introduced, firstly. And then, a SSRs‐loaded electromagnetic transparent antenna (ETA) is designed to suppress the scattering interference existing in the proposed dual‐band shared‐aperture antenna (P‐DBSA). The P‐DBSA is composed of the proposed ETA operating in the lower‐band (LB: 1.7–2.2 GHz) and a 2 × 2 array antenna operating in the higher‐band (HB: 3.4–3.6 GHz). The proposed ETA is obtained by etching folded split‐slot resonators (F‐SSRs) on the entire radiating arms of the LB antenna. In this way, the scattered field formed by the HB‐induced current distributed on the LB radiating arms can be self‐canceled, thereby HB radiation pattern restoration can be achieved. In addition, etching F‐SSRs will not cause the ETA to be difficult to match. The proposed decoupling method has the advantages of simple in structure, high integration, and easy to manufacture, and has important reference value for suppressing cross‐band scattering existing in DBSAs. [ABSTRACT FROM AUTHOR]

A low‐profile dual‐band dual‐polarized base station antenna array is proposed. The dual‐band array is backed by an artificial magnetic conductor (AMC) surface. The AMC achieves profile reduction to 0.159 λL0 in the low band (LB), but it acts as a bandpass metasurface in the high band (HB). The nested design of AMC unit cell creates two out‐of‐phase induced currents with lower intensities, enabling suppression and cancelation of HB scattered fields. The back cavities establish clear and independent radiating environments for the LB and HB antennas. They aid in further radiation pattern restoration and antenna profile reduction. The proposed antenna array was fabricated and experimentally measured. The simulated and measured results are presented. The operating principles of the proposed AMC and back cavities are also investigated. [ABSTRACT FROM AUTHOR]

This article presents a novel circularly polarized (CP) open‐ended waveguide antenna array based on additive manufacturing technology. It is a one‐dimensional four‐element linear array and has a single piece configuration. Its main body is made of dielectric material and partial surfaces are coated by copper films through electroplating to form necessary metal components. Regarding to each element, it is based on a circular waveguide and employs an inbuilt linearly tapered double‐ridge structure to act as a polarizer. To design such a polarizer, different shaped ridges are analyzed and a design evolution is presented and discussed. Compared to the conventional designs, the proposed element and array can avoid structure partitioning during the processing, and effectively reduce the fabrication difficulty and complexity, meanwhile, attain light weights. To validate the design idea, two prototypes corresponding to the element and the array are fabricated and tested. Experimental results indicate that their axial ratio bandwidth (ARBW) are 22% (8.9–11.1 GHz) and 11.8% (9.6–10.8 GHz), and the gain are 6.6 ± 1.1 and 10.6 ± 0.6 dBic, respectively. The proposed element and array could be potentially applied for satellite and other CP communication systems. [ABSTRACT FROM AUTHOR]

An antenna decoupling method based on modal control is proposed in this paper. Different from the previous characteristic mode decoupling methods, which excite one of the characteristic modes from each port, a pair of decoupling modes is excited simultaneously at each port. To validate our method, a head‐to‐head antenna pair is analyzed and designed. According to the characteristic mode analysis, an inductor‐loaded coupled sheet is introduced for the head‐to‐head antenna pair. Thus, the resonant frequencies of decoupling modes can be tuned individually. To further demonstrate the flexibility of our design, an eight‐element multiple‐input multiple‐output (MIMO) antenna composed of two integrated four‐element blocks is designed, fabricated, and measured. The proposed antennas show good impedance matching, isolation, and diversity performance varying from 3.35 to 3.71 GHz. Both simulated and measured results show the 8 × 8 MIMO system can achieve isolations of better than 11.5 dB and envelope correlation coefficients of less than 0.2 of each port. [ABSTRACT FROM AUTHOR]

This paper presents a wideband circularly polarized (CP) multibeam antenna array, which is with full azimuth scanning capability and operates in Ka band for 5G applications. It adopts a circular array configuration and consists of 18 elements with a simple structure. Regarding to each element, it is fed by a 90° bent rectangular waveguide and employs a simplified single dielectric slab polarizer to produce CP waves. Within the axial ratio bandwidth (ARBW), the proposed element can achieve a stable half power beamwidth (HPBW) of 29 ± 7°, while, the 3‐dB AR beamwidth is larger than the HPBW. By switching the active elements, the proposed array can realize 360° beam steering in azimuth plane, while, the HPBW and the 3‐dB AR beamwidth cover the entire plane. To simplify the fabrication process, dielectric and metal 3‐D printing technologies are employed for processing. Experimental results indicate that the proposed array can achieve a 40.5% 3‐dB ARBW which almost covers the entire Ka band from 26.2 to 39.5 GHz and a gain of 9.9 ± 1.5 dBic. The front‐to‐back ratio (FBR) of each beam is higher than 19 dB. In contrast to conventional designs, the proposed antenna features wide band, simple structure, and ease of fabrication. [ABSTRACT FROM AUTHOR]

In this article, a height‐reduction dual‐polarized antenna suitable for base station applications with a simple structure is proposed. By adopting the form of bilateral coupling feed, the height of the antenna has been significantly reduced. The working mechanism of height‐reduction of the antenna is given. The experimental results show that the antenna operates at 0.698–0.96 GHz for reflection coefficient <−12 dB with isolation (ISO) of more than 30 dB. It has a stable gain of 8.4 ± 0.6 dBi and a half‐power beamwidth (HPBW) of 66.8 ± 6.8° in the working band, and the height of the proposed antenna is only 0.115λ0, which is much smaller than the traditional 0.25λ0 (λ0 denotes the free wavelength corresponding to the center frequency). [ABSTRACT FROM AUTHOR]

A tri‐band dual‐polarized antenna array for base station applications is presented. The proposed tri‐band antenna array is devised by stacking the 1 middle‐band (MB) + 4 high‐band (HB) interleaved array above the low‐band (LB) patch antenna. The MB antenna yields partial reflection to the HB subarrays, enabling cross‐band and in‐band decoupling abilities without introducing additional decoupling layer. With the aid of spatial cancelation and partition, transmission nulls are successfully generated in the in‐band mutual coupling curves. Measured results show that good impedance matchings and polarization isolations are acquired in the operating bandwidths. The measured co‐ and cross‐polarized in‐band isolations in the HB are improved to >22.4 dB and >29.1 dB, respectively. The HB radiation patterns are well restored. [ABSTRACT FROM AUTHOR]

This paper presents a triple‐band composite antenna array for maritime application. It consists of a three‐element base station antenna array and a waveguide based satellite antenna, which are applied for near‐shore and long distance off‐shore communications, respectively. For the former, it is a ±45° dual polarized array with dipole radiators and covers 2G/3G/4G bands. The three elements are arranged in a form of half hexagon and attain 180° coverage of half power beamwidth (HPBW) in azimuth plane by switching the feeding ports. For the latter, it is a sequentially fed circularly polarized antenna operating in Ku‐band and has a wide HPBW through loading a dielectric structure. To validate the design idea, a prototype is fabricated and measured. Experimental results show that the base station antenna array achieves wide bandwidth of 49.14% from 0.66 to 1.09 GHz and 46.58% from 1.68 to 2.7 GHz with VSWR < 1.5. Meanwhile, the satellite antenna has a wide 3‐dB axial ratio (AR) bandwidth of 20.1% from 12.1 to 14.8 GHz with reflection coefficients lower than −15 dB. Within the band, the HPBW is larger than 90° and the 3‐dB AR beamwidth covers the HPBW. [ABSTRACT FROM AUTHOR]

A high‐isolation dual‐band base station antenna array is proposed. At first, a 5‐element high‐band (HB) dipole antenna array with inter‐element distance of 0.4 λH0 (the free‐space wavelength at the center frequency of the HB) is decoupled. With the main antenna decoupling surface (ADS), metal baffles and auxiliary ADS, the E‐plane and H‐plane couplings can be reduced to <−23.1 dB (<−11.4 dB without decoupling) and <−22.6 dB (<−14.8 dB without decoupling), respectively. The dual‐layer ADS design successfully resolves the contradiction between decoupling performance and matching. The ground plane of the 5‐element array is then exploited as the low‐band patch radiator, forming the proposed dual‐band antenna array. Measured results show that satisfactory cross‐band isolation (>33.1 dB), in‐band isolation (>22.2 dB) and polarization isolation (>30 dB) are obtained. Stable unidirectional radiation patterns are also acquired. [ABSTRACT FROM AUTHOR]

This article presents a circularly polarized (CP) endfire multibeam antenna with wide axial ratio (AR) beamwidth coverage. It is based on a dielectric loaded waveguide structure and consists of a 4 × 4 Butler matrix and four rhombic waveguide elements. Regarding to each element, it decomposes the incoming linearly polarized waves into two orthogonal modes with equal amplitude and obtains 90° phase difference between the two modes via their different dispersion characteristics to realize CP radiation. Study found that the proposed element has low cross‐polarization performance within a wide beamwidth, which contributes to realize wide 3‐dB AR beamwidth coverage in the multibeam array. In fabrication process, injection modeling and electroplating techniques are employed to construct the proposed antenna. By using this way, the structure splitting and misalignment problems, which usually existed in conventional designs, can be avoided, and the antenna weight can be maintained to a moderate level. Through the experiment, it is found that the proposed antenna can achieve an overlapped 3‐dB AR bandwidth of 10.7% from 9.7 to 10.8 GHz and a wide 3‐dB AR beamwidth coverage of 91°. [ABSTRACT FROM AUTHOR]

A wide‐band circularly polarized reconfigurable antenna based on a pure water dielectric patch antenna is proposed. By changing the shape of pure water in the plexiglass container symmetrically, the circularly polarized states of the antenna can be switched. And the available bandwidth of right‐hand circular polarization and left‐hand circular polarization remain unchanged. The interface between pure water and air with a great difference in relative dielectric constant is equivalent to an electrical wall. When feed with an L‐shaped metallic probe, the axial ratio of a wide band can be formed, and the impedance bandwidth of antenna can be fully utilized. Under the two circularly polarized states of the antenna, the measured results show that the 3‐dB axial ratio bandwidth is above 24.4% for |S11| < −10 dB, the radiation efficiency is concentrated at 58%–71%, and the maximum gain reaches 3.5 dBi. [ABSTRACT FROM AUTHOR]

A compact differentially fed dual‐polarized patch antenna with filtering performance is proposed for 5G applications. By utilizing the half‐wavelength standing current along the open‐ended microstrip line, the out‐of‐phase output signals are obtained. Utilizing the E‐shaped coupled resonator in series with the open‐ended microstrip line, balanced differential feeding with filtering property are realized, as excitation for the patch. The filtering patch antenna was fabricated for demonstration. Measured results show that the antenna has −15 dB impedance bandwidths of 13.7% (3.26–3.74 GHz) and 14.2% (3.25–3.75 GHz) for two polarizations, respectively, covering the 5G band (3.3–3.6 GHz). The patch antenna achieves good port isolation and cross‐polarization discrimination. In addition, the measured gain is higher than 6.8 dBi within operating band. Out of the operating band, the gain drops sharply, exhibiting a bandpass response. The out‐of‐band radiation suppression level of the proposed filtering patch antenna is larger than 16 dB. [ABSTRACT FROM AUTHOR]

In this article, dielectric loading is introduced as a method for miniaturizing dual‐polarized crossed dipole antenna. Specifically, the size, thickness, and relative permittivity of dielectric slab are considered as three critical parameters for antenna miniaturization. It is found that the three parameters have different loading effects on a crossed dipole, due to distinct modal current and field distributions. Furthermore, an antenna configuration loaded by 3‐layer dielectric slabs is proposed. Utilizing the slow‐wave property of dielectric loading, two miniaturized crossed dipole antennas with size of 40 mm × 40 mm (0.29 λ0 × 0.29 λ0) are devised, exhibiting an at least 21% size reduction over the previous dual‐linearly‐polarized crossed dipole antennas. Simulated and measured results demonstrate that the proposed antennas have wide bandwidth (1.71‐2.69 GHz), desirable impedance matching (VSWR <1.5), stable radiation pattern, and low gain loss. [ABSTRACT FROM AUTHOR]

Different from the traditional reconfigurable antennas, in which PIN diodes are just used as switches, a novel method for achieving the reactance tuning is proposed, in which the impedance characteristics of the PIN diode in different working states are used to realize elements sharing. The mechanism of element sharing is explained by mathematical analysis, firstly. Then, the novel method of realizing element sharing based on the impedance characteristics of PIN diode is explained. By this way, reactance tuning can be easily achieved using PIN diode. Finally, a 360° beam switchable dipole antenna array is designed to illustrate the feasibility of the proposed method. The results show that gains of 7.8 dBi, and FBRs (front‐to‐back ratios) of greater than 19 dB are achieved by the proposed antenna. In particular, the maximum gain drop of the proposed antenna is less than 0.72 dB when switching between different working modes. [ABSTRACT FROM AUTHOR]

A miniaturized, loop resonators (LRs)‐loaded, circularly polarized (CP) multi‐dipole antenna with wide axial‐ratio (AR) beamwidth is proposed and demonstrated in this article. The radiator of this CP antenna consists of two pairs of parallel dipoles loaded with four LRs at their corners. By increasing the length of the LR, or decreasing the coupling space between the dipole and the LR, the effective length of the dipole can be lengthened significantly and thus the working frequency can be reduced without increasing the whole aperture size. As a result, a miniaturized radiator structure is completed. A feeding network consisting of a T‐shaped coupling feeding structure and four coplanar striplines having different lengths are specially designed to feed these dipoles with approximately the same magnitude and 90° phase quadrature. What is more, a cavity reflector is employed to achieve a unidirectional radiation with wide axial‐ratio beamwidth. The radiator of the proposed CP antenna has a small aperture size of only 0.34λ0 × 0.34λ0, where λ0 is the free space wavelength at the working frequency. Measured results are in a good agreement with the corresponding simulated counterparts. Especially, the experimental results show that the antenna has achieved a wide AR beamwidth of 182° and 174° at the center frequency in the xoz and yoz planes, respectively. [ABSTRACT FROM AUTHOR]

A novel dispersion formulation of the 2D alternating-direction implicit (ADI) finite-difference time-domain (FDTD) method is presented. The formulation is based on an increasing process analysis of the monochromatic wave in free space. A numerical experiment scheme is designed to verify the accuracy of the proposed formulation. The results obtained from the proposed formulation are in a good agreement with those from the numerical experiments, and the proposed formulation is more accurate than those reported in the literature. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006. [ABSTRACT FROM AUTHOR]