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Two circularly polarized (CP) 2 × 2 array antennas based on the spoof surface plasmon polariton (SPP) and spoof localized surface plasmon (LSP) are proposed. The antenna I is fed by a feed network to increase the axial-ratio (AR) bandwidth. The spoof SPP and spoof LSP are introduced to increase the gain through energy localization, and the structure can suppress the cross-polarization to a certain extent and obtain a wider axial-ratio beamwidth. In addition, the electromagnetic band gap (EBG) is used to suppress surface waves to further increase the gain. The size of antenna I is 1.27λg × 1.27λg × 0.18λg. The impedance bandwidth and the AR bandwidth of antenna I are 72% (3.15–6.75 GHz) and 55% (3.97–6.72 GHz), respectively, and the peak gain is 11.11 dBi. The antenna II optimizes the distance between the two substrates according to antenna I to further increase the gain. [ABSTRACT FROM AUTHOR]

In this paper, a simple broadband circularly polarized (CP) patch antenna design is proposed. The antenna uses a 2 × 2 array fed by a sequential-phase feed network to improve the axial ratio (AR) bandwidth and gain, and an L-shaped slot is used to remove the coupling between the feed network and the radiation patches. Similarly, to reduce coupling, the height between two substrates is discussed as an important parameter. The proposed antenna is fabricated to verify the simulated results. Measured results show that the impedance bandwidth is 65.2% (1.68–3.31 GHz), the AR bandwidth obtained at the same time is 61.6% (1.86–3.39 GHz), and the effective relative bandwidth is 58% (1.86–3.31 GHz), and the peak gain is about 7.13 dBi at 2.7 GHz. [ABSTRACT FROM AUTHOR]

In this article, a 2×2 broadband circularly polarized antenna array using the sequential rotation (SR) technique in the feed network is presented. This antenna covers the 5G-band of 3.5–3.6 GHz and 4.8–4.9 GHz. So, it can be used for 5G-band communication [1]. The performance of the antenna is obtained by simulation and experiment, as follows: the bandwidth of S11 parameter below -10 dB is 3.7 GHz (3.3–7 GHz), and AR bandwidth (AR < 3 dB) is 2.4 GHz (3.5–5.5 GHz and 5.8-6.2 GHz), the maximum gain is about 10.2 dBi, and the gain is greater than 0 dBi in the range of 3.6–6.5 GHz. [ABSTRACT FROM AUTHOR]

With the rapid development of industrial production and aerospace, how to measure the plasma density has also developed rapidly. So a radio-frequency plasma transducer based on a three-layer dielectric substrate antenna with a high dielectric constant is introduced. The top and bottom layers are dielectric plates, which protect the internal antenna structure and improve the equivalent permittivity of the antenna. The middle layer is the structure layer of the designed antenna. And the antenna size is 3.8 × 2 × 1.8 mm3. When the plasma frequency changes from 0.3 GHz to 7 GHz, the corresponding dielectric substrate antenna resonant frequency (RF) changes from 4.076 to 5.213 GHz. The minimum unit is 0.1 GHz, and all the measurement accuracy is more than 90%. The method based on the effective dielectric constant of plasma will change under different plasma frequencies, so the RF of the antenna is different. In this paper, the radio-frequency plasma transducer is studied theoretically and analyzed numerically. [ABSTRACT FROM AUTHOR]

In this paper, a novel broadband flexible metamaterial absorber, which is based on high impedance surface (HIS), has been investigated. The polarization-insensitive absorber can suppress the backward RCS by about 10 dBm2. Numerically simulated results indicate that the HIS metamaterial absorber (HIS-MA) obtains 11.14 GHz wide absorption from 6.86 to 18 GHz with the absorption over 90%. The results of experiment coincide with simulations, which prove the feasibility of HIS-MA. The flexibility and absorption performance of the HIS-MA is demonstrated by simulating and measuring the absorptivity as the absorber is bended on cylinders, which can obtain some novel properties. The simulated results of bistatic RCS showed that the bistatic RCS of HIS-MA bended on a cylindrical object is reduced by nearly 10 dBm2compared with the conventional planar HIS-MA. The proposed absorber has more advantages in conformal applications than ordinary rigid absorber in its stealth property. [ABSTRACT FROM PUBLISHER]

In this paper, the magneto-optical Faraday effects in the properties of anisotropic photonic band gaps (PBGs) and surface plasmon modes for the three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) with body-centered cubic lattices are theoretically studied based on the modified plane wave expansion (PWE) method, in which the homogeneous Te (tellurium) spheres are immersed in the homogeneous magnetized plasma background, as the mixed polarized waves are considered. A more general case is investigated, and the anisotropic PBGs are not only for the left- and right-circular polarized waves but also for the mixed polarized waves. The equations for computing those anisotropic PBGs for all of the electromagnetic waves in such 3D MPPCs are theoretically deduced. Theoretical simulations show that the anisotropic PBGs and a flatbands region can be observed. Compared to the similar 3D MPPCs containing the isotropic dielectric or uniaxial material spheres, the largest PBG can be obtained as the extraordinary axis of inserted uniaxial material is along the Г-Hsymmetry line. The larger PBGs can also be achieved compared to the conventional PBGs for the right-circular polarized wave as the mixed polarized waves are considered. The interesting properties of surface plasmon modes can also be found, which are the upper edge of flatbands region cannot be tuned by the filling factor but almost can be linearly increased with increasing the plasma frequency and plasma cyclotron frequency, respectively. The effects of the filling factor, plasma frequency, and plasma cyclotron frequency (the external magnetic field) on the anisotropic PBGs are also investigated in detail. Theoretical simulations also show that such PBGs can be manipulated by the parameters as mentioned above. [ABSTRACT FROM AUTHOR]

In this paper, the surface plasmon modes and switching gaps of three-dimensional (3D) photonic crystals (PCs) with diamond lattices, which are composed of core isotropic dielectric spheres surrounded by plasma shells inserted in air, are theoretically investigated in detail based on a modified plane wave expansion method. The equations for computing band structures for such 3D PCs are presented. Our analyses show that the proposed double-shell structure can produce the complete photonic band gaps (PBGs) which can be worked as an optical switching by manipulating the parameters of such PCs. However, the switching state cannot be tuned by the plasma collision frequency. Numerical results also demonstrate that a flatbands region and the stop band gaps (SBGs) in the (1?0?0) and (1?1?1) directions which are above the flatbands region can be achieved. The SBGs also can be tuned by the parameters as mentioned above. There is also a threshold value for the thickness of plasma shell, which can make the band structures of the 3D PCs with double-shell structures similar to those obtained from the same PC structure containing the pure plasma spheres. In this case, the dielectric function of the inserted core sphere will not affect the band structures. It means that the PBGs can be achieved by replacing the pure plasma spheres with such double-shell structures to make fabrication possible and save the material in the realization. It is also noticed that the flatbands region is determined by the existence of surface plasmon modes, and the upper edge of flatbands region does not depend on the topology of lattice. [ABSTRACT FROM AUTHOR]

The Voigt effects in dispersive properties of three-dimensional magnetized plasma photonic crystals (magnetized plasma spheres immersed in dielectric background), composed of homogeneous dielectric and magnetized plasma with face-centered-cubic lattices are theoretically investigated based on the plane wave expansion method, as incidence electromagnetic wave vector is perpendicular to the external magnetic field. The equations for calculating the band diagrams are theoretically deduced. The influences of dielectric constant of dielectric, plasma collision frequency, filling factor, plasma cyclotron frequency, and plasma frequency on the dispersive properties are studied in detail, respectively, and some corresponding physical explanations are also given. From the numerical results, it has been shown that the photonic band gap (PBG) can be manipulated by plasma frequency, filling factor, plasma cyclotron frequency, and the relative dielectric constant of dielectric, respectively. However, the plasma collision frequency has no effects on the location and relative bandwidth of the PBG. The locations of two flatbands regions cannot be tuned by any parameters except for plasma frequency and plasma cyclotron frequency. [ABSTRACT FROM AUTHOR]

A broadband omnidirectional absorber which is realized by heterostructures containing a collision plasma layer and a ternary plasma Bragg mirror is theoretically investigated. A collision plasma layer and an appropriate dielectric layer are put on the top of the ternary plasma photonic crystals to obtain a broadband omnidirectional absorption. It is shown to absorb roughly 70% of all available electromagnetic wave in a relative omnidirectional absorption band width 0.58 GHz with plasma width 3 mm in PCs. The band edges are impacted by the range of reflection band gap and the absorption range for transverse magnetic (TM) wave decreases at large incidence. Compared with some previous designs, our proposed structure has a relative flatter total absorption spectrum over a broad frequency range in microwave. This kind of hererostructures offer additional opportunities to design novel optoelectronic devices. [ABSTRACT FROM AUTHOR]