A novel compact wideband dual-polarized printed dipole antenna for base station application is presented. The proposed antenna is composed of four assembled substrates. Two pairs of identical arrow-shaped conductive lines on the tophat substrate form two orthogonal polarized dipoles. Two baluns connected with 50 Ω coaxial cables are integrated on another two vertical substrates to excite the dipoles. The other horizontal board at bottom provides grounding. A rectangular box-shaped reflector is also used to enhance its stability in radiation patterns over the operating frequencies. It achieves 22% size reduction from the conventional printed half-wavelength cross-dipole, and 43.2% impedance bandwidth (VSWR<2), while maintaining a stable radiation pattern with measured Cross-Polarization Degradation (XPD) better than -22dB at boresight and an average peak gain of 8.4 dBi for a 65° Azimuth Beamwidth base station application at 700/800/900 MHz bands. With the scalable miniature structure, it may also find itself suitable for side-by-side multiband Multi-Input Multi-Output (MIMO) or Large-Scale Antenna (LSA) 5G base station applications. A 4x4 array prototype of the LSA is also designed and fabricated, and it achieves 27.8% impedance bandwidth (VSWR<1.5) with well decorrelated element performance and array XPD better than -20 dB across as large as 30° tilting range.
This paper presents the comprehensive design and analysis of a tri-band bandpass filter (BPF) based on a novel quad-mode defected ground structure resonator (QMDGSR) fed by two 50 Ω microstrip lines under the source-load coupling condition. Four transmission zeros (TZs) are produced in the proposed tri-band bandpass structure with two TZs beside each passband. All the four TZs are thoroughly analysed using equivalent circuit models based on the even-/odd-mode theory, and the corresponding equation for extracting the frequency of each TZ is developed and verified. The bandwidths (BWs) of the 1st and 3rd operating bands are broadened by incorporating the proposed triband bandpass structure with a traditional microstrip stepped impedance resonator (MSIR). Also, two additional TZs are generated due to the coupling between the feeding lines and the newly incorporated MSIR, which significantly result in the passband selectivity improvement. The lower and upper stopband rejections of the fabricated prototype are as high as 83.3 and 43.9 dB, respectively.
A low-radar cross section (RCS) coding metasurface (MS) with properties of absorption and diffusion for both normal and oblique incidences is proposed in this paper. The coding MS is composed of a miniaturized perfect metamaterial absorber (PMA) and a wideband artificial magnetic conductor (AMC) in a shared aperture. In addition, to avoid strong scattering energy appearing at specific directions, genetic algorithm (GA) is adopted to search the optimal layout of the two MS elements. Simulated and experimental results confirm the properties of coding MS and indicate the 6-dB RCS reduction bands under TE- and TM-polarized normal incident that waves are 6.28GHz-9.16GHz and 6.33GHz-9.41GHz, respectively.
In this work, we present a three-component hierarchical structure to simultaneously improve the red, green, and blue (RGB) light-extraction efficiency (LEE) of white light-emitting diodes (LEDs) based on color mixing method. With the help of 3D finite-difference time-domain (FDTD) simulations, the effects of the embedded photonic crystals (PhCs), the normal surface PhCs, and the nano-rods on the enhancement of RGB light extraction were investigated. The results were compared with those of the conventional planar LEDs and the normal surface PhCs LEDs over the whole visible spectrum. Results from the simulations demonstrated that the maximum LEE for the hierarchical structures LEDs gave 112%, 327%, and 284% RGB LEE enhancement, respectively, compared to that of the conventional planar LEDs, and achieved 104%, 191%, and 187% RGB LEE enhancement compared to that of LEDs with normal surface PhCs. The emission characteristics of the hierarchical structures LEDs were also revealed in detail by FDTD simulations. The results shown in this paper would do a favor for the design and fabrication of high efficiency LEDs.
In magnetic induction communication systems, channel capacity is often a major bottleneck that limits the system performance. This paper proposes a method to increase the channel capacity in such systems by means of an antenna array. A central challenge in the design of magnetic antenna arrays is to achieve low intra-array coupling along with high gain. These two properties are essential for increasing the channel capacity in comparison to single antenna communication systems of comparable volume. The method proposed in this paper utilizes circular loop antennas to reduce the intra-array coupling using magnetic flux cancellation. The mathematic approach employed in this paper considers each coil as a system of coupled inductors, where each inductor is a single turn loop, and the total coil self and mutual inductances are computed by summing the appropriate single turn loop inductances. Volume efficient coil topologies are identified, and an optimization method is proposed to minimize the intra-array coupling, subject to a required inductance. The proposed method allows to design volume efficient, up to 3×3, array, or pyramidal shaped 4×4 arrays. The results are verified experimentally using the multiple-frequency communication mode.
In this work, different configurations of electrically reconfigurable radial waveguides are presented: a configuration with pass/stop regions, a configuration with tunable narrowband filters and a configuration with integrated phase shifters. Potential applications for the different configurations are also proposed. First, the design and experimental results for a reconfigurable radial waveguide using PIN diodes and operating in the band 5.2-5.8 GHz (11%) are presented and discussed. Then, the principle of radial waveguide with tunable narrowband filters using varactors is described and an application for Frequency Modulated Continuous Wave (FMCW) radars is proposed. Finally, a new radial-line slot array antenna with electrically beam-steering ability is proposed.
An efficient method based on the recursive fast Fourier transform (FFT) to incorporate both the intra-band and inter-band conductivity terms of graphene into the finite-difference time-domain (FDTD) method is proposed. As it only requires numerical values of the conductivity, it not only does not enforce any restrictions on the conductivity models, but also can directly take into account material properties obtained from measurement. It reduces the total computational cost from O(N2) to O(Nlog2N) where N is the length of the unknown. The FDTD method is also modified and proven to retain the stability condition of the standard FDTD method.
A miniaturized frequency selective surface (MFSS) that has very stable performance is designed based on the stepped-impedance element (SIE) structure. Significant couplings can be introduced by overlapping one metallic layer above the SIE structure. The large overlapping areas between the two metallic layers is beneficial to further miniaturizing the element size. Therefore, the physical size of the MFSS unit cell can be reduced to 0.054λX0.054λ. In addition, the MFSS is proved to excellent stability towards incident angles (up to 75o) and polarizations. A careful equivalent circuit model is presented to explain the physical principle of the proposed design. Finally, a prototype is fabricated and tested, and the simulation results are in agreement with the experimental observations.
A compact ultra-wideband planar monopole antenna with a notched band at WLAN frequencies is presented. The antenna is fed using a finite ground coplanar waveguide and has a structure consisting of stair-shaped radiator and ground plane. The notched band is implemented by cutting two symmetrical narrow slits from the ground plane. The antenna is fabricated on a substrate with a dielectric constant of 4.4 and has a compact size of 18×26×1.6 mm3. Experimental and simulation results of the fabricated antenna are found to be in good agreement. The antenna achieves an average gain of 3 dBi and efficiency of more than 80% over the operational band. Time domain analysis, which includes the group delay response and fidelity calculation, implies that minimal distortion is introduced by the proposed antenna which makes it suitable for portable pulsed UWB systems.
Due to the influence of aerodynamic forces, the wing will be subjected to vibration and deformation. This will result in a severe performance degradation of the wing conformal antenna. To solve this problem, a new gain-phase error compensation method based on the deformation fitting of wing conformal antenna is proposed. In this proposed method, the array deformed shape curve is fitted through the gain error of the array, thus the position of each element can be calculated. Finally, by using the position of the elements to calibrate the gain-phase error, the corrected directions of arrival (DOA) estimation angle is obtained. Simulation results show that the proposed method can well reproduce the shape of the array, and effectively compensate the position error caused by the vibration of the wing conformal antenna.
The scattering of the electromagnetic waves by the spherical particles is discussed. Nanometer-sized dielectric spheres confined in a cluster are devoted to investigate the effect of the EM radiation on them. Incident wave is considered to be in visible light spectrum which facilitates multiple scattering calculation for nanoparticles. Radiation forces are discussed in terms of scattering pressure and Lorentz force, hence Discrete Dipole Approximation (DDA) and classical Mie theory is employed in radiation force computation and electromagnetic random multiple scattering analysis. Electric momentum of dipoles is defined in the term of A-1 term method. The radiation forces on particles are accurately calculated with computer codes. Extracted results can be applied to conscious deviation of spherical nanoparticles in clean rooms or similar mediums. The effect of the incident wave parameters and the orientation of spherical profile and particles in the cluster are predicted through various simulations.
A quarter-wavelength folded patch antenna is adopted as the passive wireless strain sensor for structural health monitoring (SHM) of bridges. It can be used for continuous surveillance and damage detection. According to theoretical formulations, strain simulation and experiments, it is found that a good linearity relationship can be achieved between normalized resonance frequency shift and the strain both in longitudinal and transverse directions. And the sensing sensitivity in longitudinal strain is better than that in transverse strain. Through conducting tensile experiments, we find that many factors can influence the strain sensitivity. To address this fundamental issue in antenna sensors for strain sensing, a new strain sensitivity experiment is proposed to take the influence of strain transfer ratio change under strain. The linear relationship of strain transfer ratio and deformation is obtained by sensitivity experiment. The corrected sensitivity in longitudinal and transverse strains is calculated based on the linearity. Furthermore, the Possion effect is taken into consideration to explain the opposite effects of experimental and simulated sensitivities in transverse strain.
A multi-band antenna with omnidirectional radiation performance is proposed, which consists of 9 elements to form the structure of hexagonal prism. According to the placement rule, the antenna elements can be divided into two groups, one of which is placed in parallel on spaced three surfaces of the prism and the other placed vertically on the remaining spaced three faces of the prism. Each parallel element consists of two coplanar microstrip radiating patches which are nested within each other for miniaturization. Two parallel microstrips connected by a grounded disc with shorting pin are placed between the two patches to optimize the isolations. Each vertical element consists of two improved dipoles with four arms and a BALUN located at the back of the substrate plate which constitutes the quasi-Yagi structure. The resonant frequencies of the proposed prismatic antenna are 3.45 GHz, 4.9 GHz, 5.8 GHz and15.2 GHz which can be used for low frequency bands of the fifth generation (5G) wireless communications and wireless local area networks (WLAN) as well as satellite communication applications.
A compact 2×1 multiple input multiple output (MIMO) antenna system is designed to operate in the LTE band 40 (2.3-2.4) GHz. The proposed antenna consists of two circular patches fed using microstrip line. The antenna was initially designed to resonate at 5 GHz. Size reduction of 55.17% compared to conventional patch antenna is obtained after the inclusion of circular complementary split ring resonator (CSRR) in the ground plane. The resonating frequency was shifted to 2.34 GHz, there by the board size is compact (50×25×1.6 mm3). The designed antenna covers a bandwidth of 2.3 to 2.374 GHz with a maximum return loss of -27 dB at 2.34 GHz and isolation of -33.5 dB between the ports. The simulated correlation coefficient is approximately zero, and the total active reflection coefficient is 0.142 at the resonating frequency which are within the acceptable limits. The realized gain for the antenna is -8.9 dB.
A plasmonic induced transparency (PIT) structure is proposed and numerically investigated using the finite difference time domain (FDTD) method, which is achieved by the destructive interference between two graphene nano ribbon resonators and the bus waveguide. The common three-level atom system is used to explore the physical origin of the PIT behavior. The simulation results show that the PIT at different modes can be excited or suppressed by choosing the proper coupling position of the resonators. The peak and bandwidth of the transparent window are controlled by the coupling distance between the resonators and the bus waveguide, and the transparent window can be freely tuned by adjusting the chemical potential of graphene. The tunable PIT effect may offer a new avenue for novel integrated optical switching and slow-light devices in THz and mid-infrared frequencies.
In this paper, a three-layer circuit structure based on double-sided parallel-strip lines (DSPSLs) is proposed to design one out-of-phase power divider (PD) with equal power division and harmonic suppression. This PD, which is composed of four DSPSLs, one middle conductor, and two grounded resistors, features transmission suppression at two specified frequencies and all the even-order harmonics. Closed-form design equations are derived based on the traditional even- and odd-mode methods, and the circuit scattering parameters are also given. Finally, a practical PD operating at 0.92 GHz is designed and fabricated. The measured results show that this PD has equal power division with out of phase, harmonic suppression, good ports matching, and high outputs isolation.
This paper presents the design of a flexible antenna using planar dipole with a reflector to achieve optimal radiation efficiency and low specific absorption rate (SAR) when the antenna is placed directly over the skin of body model. The antenna is designed for the 2.45 GHz frequency band. The parametric analysis of the proposed antenna is carried out. The proposed antenna achieves stable on-body performance: |S11| varies from -16.05 dB (on skin) at 2.47 GHz resonant frequency to -16.40 dB (on skin) at 2.47 GHz resonant frequency to -16.40 dB (in free space) at 2.44 GHz resonant frequency. It was found that the maximum 1 g average SAR value is only 0.23 W/kg for an input power of 100 mW when the antenna is placed directly over the skin of a three-layer body model, and radiation efficiency is 20.5%. The measured results are presented to demonstrate the validity of the proposed antenna.
Iron-nickel nanotubes consisting of 20% of Ni and 80% of Fe with an aspect ratio of about 100 were synthesized by electrochemical deposition in the pores of the polyethylene terephthalate ion-track membranes. The main morphological parameters such as composition, wall thickness and structural characteristics were defined. Macro- and micromagnetic parameters of FeNi nanotubes were determined.
Metamaterials left-hand negative refractive index has remarkable optical properties; this paper presents the results obtained from the study of a flat metamaterial lens. Particular interest is given to the interaction of electromagnetic waves with metamaterials in the structure of the lens Pendry. Using the new approach of the Wave Concept Iterative Process (WCIP) based on the auxiliary sources helps to visualize the behavior of the electric field in the metamaterial band and outside of its interfaces. The simulation results show an amplification of evanescent waves in the metamaterials with an index of n = -1, which corresponds to a resonance phenomenon to which the attenuation solution is canceled, leaving only the actual growth of these waves. This amplification permits the reconstruction of the image of the source with a higher resolution.
The propagation characteristics of a composite right/left-handed (CRLH) waveguide loaded with air-filled double ridge corrugations (DRCs) is studied intensively in this paper. It is analyzed from the perspective of electromagnetic (EM) fields other than equivalent circuit method used by many other CRLH structures. First, the EM fields inside the CRLH waveguide are derived theoretically based on the EM fields in the rectangular waveguide and the DRC, as well as the boundary conditions on the interface, respectively. Then the propagation characteristics of the CRLH waveguide including the dispersion relation, surface current and transmitted power are determined according to the EM fields. The properties of the surface current are focused on for analyzing the application possibility of this CRLH waveguide to the leaky-wave antennas (LWAs). The transmitted power of the CRLH waveguide is calculated to demonstrate the high power capacitance of this CRLH waveguide. All the theoretical results are veried through full-wave simulations.