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Phased Transmitarray Antennas for 1-D Beam Scanning
摘要： A transmitarray antenna (TAA) fed by a phased array antenna (PAA) for one-dimensional (1-D) beam scanning is proposed at 10 GHz in this letter. The TAA is composed of two types of elements, i.e., the hexagonal subwavelength low-pass elements as well as the pure dielectric ones. The PAA feed is a 1-D printed dipole array loaded with the short-circuited dummy ones. The proposed PAA-fed TAA, with a feeding distance to TAA diameter ratio (H/D) of mere 0.375, achieves a peak simulated gain of 25.6 dBi at 0o scanning (corresponding to peak aperture efficiency of 57.5%) and a 3.13 dB gain drop for ±30o beam scanning, along with a ~2-dB beam crossover. The measured results agree reasonably well with the simulated ones, validating the proposed design.
关键词： periodic structures,phased array antennas,transmitarray antennas,Beam scanning
更新于2025-09-23 15:22:29
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The role of plasmonic excitations in the optical activity of periodic structures with configurational chirality
摘要： Broken mirror symmetry of chiral structures imposes a lack of mirror symmetry in the scattering pro?le. When an energy dissipation channel is introduced in the system, an overall optical activity arises. Plasmonic nanostructures, therefore, are an ideal platform to induce optical activity by means of constitutional or con?gurational chirality. We experimentally investigate the mechanism of plasmonically induced con?gurational chirality in a periodic monoclinic hole array with a broken mirror symmetry. The resulting optical activity of the structure is studied by using k-space leakage radiation measurements.
关键词： k-space leakage radiation measurements,plasmonic excitations,periodic structures,optical activity,configurational chirality
更新于2025-09-23 15:21:01
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Development of a Monitoring Strategy for Laser-Textured Metallic Surfaces Using a Diffractive Approach
摘要： The current status of research around the world concurs on the powerful influence of micro- and nano-textured surfaces in terms of surface functionalization. In order to characterize the manufactured topographical morphology with regard to the surface quality or homogeneity, major efforts are still required. In this work, an optical approach for the indirect evaluation of the quality and morphology of surface structures manufactured with Direct Laser Interference Patterning (DLIP) is presented. For testing the designed optical configuration, line-like surface patterns are fabricated at a 1064 nm wavelength on stainless steel with a repetitive distance of 4.9 μm, utilizing a two-beam DLIP configuration. Depending on the pulse to pulse overlap and hatch distance, different single and complex pattern geometries are produced, presenting non-homogenous and homogenous surface patterns. The developed optical system permitted the successfully classification of different pattern geometries, in particular, those showing single-scale morphology (high homogeneity). Additionally, the fabricated structures were measured using confocal microscopy method, and the obtained topographies were correlated with the recorded optical images.
关键词： homogeneity characterization,periodic structures,diffraction analysis,direct laser interference patterning,indirect surface characterization
更新于2025-09-16 10:30:52
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Longitudinal wave propagation in a one-dimensional quasi-periodic waveguide
摘要： The paper deals with the analysis of wave propagation in a general one-dimensional (1D) non-uniform waveguide featuring multiple modulations of parameters with different, arbitrarily related, spatial periods. The considered quasi-periodic waveguide, in particular, can be viewed as a model of pure periodic structures with imperfections. Effects of such imperfections on the waveguide frequency bandgaps are revealed and described by means of the method of varying amplitudes and the method of direct separation of motions. It is shown that imperfections cannot considerably degrade wave attenuation properties of 1D periodic structures, e.g. reduce widths of their frequency bandgaps. Attenuation levels and frequency bandgaps featured by the quasi-periodic waveguide are studied without imposing any restrictions on the periods of the modulations, e.g. for their ratio to be rational. For the waveguide featuring relatively small modulations with periods that are not close to each other, each of the frequency bandgaps, to the leading order of smallness, is controlled only by one of the modulations. It is shown that introducing additional spatial modulations to a pure periodic structure can enhance its wave attenuation properties, e.g. a relatively low-frequency bandgap can be induced providing vibration attenuation in frequency ranges where damping is less effective.
关键词： frequency bandgaps,quasi-periodic structures,elastic wave propagation,imperfections,dispersion relation,method of varying amplitudes
更新于2025-09-12 10:27:22
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Analysis of Scattering by Plasmonic Gratings of Circular Nanorods Using Lattice Sums Technique
摘要： A self-contained formulation for analyzing electromagnetic scattering by a significant class of planar gratings composed of plasmonic nanorods, which were infinite length along their axes, is presented. The procedure for the lattice sums technique was implemented in a cylindrical harmonic expansion method based on the generalized reflection matrix approach for full-wave scattering analysis of plasmonic gratings. The method provided a high computational efficiency and can be considered as one of the best-suited numerical tools for the optimization of plasmonic sensors and plasmonic guiding devices both having a planar geometry. Although the proposed formalism can be applied to analyze a wide class of plasmonic gratings, three configurations were studied in the manuscript. Firstly, a multilayered grating of silver nanocylinders formed analogously to photonic crystals was considered. In the region far from the resonances of a single plasmonic nanocylinder, the structure showed similar properties compared to conventional photonic crystals. When one or a few nanorods were periodically removed from the original crystal, thus forming a crystal with defects, a new band was formed in the spectral responses because of the resonant tunneling through the defect layers. The rigorous formulation of plasmonic gratings with defects was proposed for the first time. Finally, a plasmonic planar grating of metal-coated dielectric nanorods coupled to the dielectric slab was investigated from the viewpoint of design of a refractive index sensor. Dual-absorption bands attributable to the excitation of the localized surface plasmons were studied, and the near field distributions were given in both absorption bands associated with the resonances on the upper and inner surfaces of a single metal-coated nanocylinder. Resonance in the second absorption band was sensitive to the refractive index of the background medium and could be useful for the design of refractive index sensors. Also analyzed was a phase-matching condition between the evanescent space-harmonics of the plasmonic grating and the guided modes inside the slab, leading to a strong coupling.
关键词： plasmonics,refractive index sensors,scattering,bandgap structures,periodic structures
更新于2025-09-11 14:15:04
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A Wideband, Single-Layer Reflectarray Exploiting A Polarization Rotating Unit Cell
摘要： We present a new technique for designing wideband, single-layer reflectarray antennas. The proposed reflectarray exploits a wideband, polarization rotating unit cell that rotates the polarization of the reflected wave with respect to that of the incident wave by 90?. This unit cell and its mirror image were used as 1-bit spatial phase shifters capable of providing a 0?/180? phase shift over a wide bandwidth of 5.4-12.7 GHz. Using this, a reflectarray antenna with 1-bit phase quantization was designed to operate at X band with aperture dimensions of 28.8 cm × 28.8 cm and a focal length of 30 cm. A prototype of the proposed reflectarray was fabricated and characterized using a spherical near-field measurement system. We determined the antenna’s 3 dB gain bandwidth to be approximately 37.4% with a maximum realized gain of 24.2 dBi. Over its entire band of operation, the polarization purity of the antenna remains better than 13 dB and side-lobe levels of better than 12 dB were achieved.
关键词： periodic structures,Reflectarray antennas,polarization rotation,antenna arrays
更新于2025-09-10 09:29:36
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One-Step Leapfrog LOD-FDTD Method With CPML for Periodic Structures
摘要： For high efficient analysis of an obliquely incident plane wave on periodic structures, one-step leapfrog locally one-dimensional (LOD-FDTD) method is proposed in this letter. Firstly, by applying the LOD scheme into the improved split-field algorithm, unconditional stability can be achieved. And then, by introducing three auxiliary variables, the one-step leapfrog implementation for the LOD scheme is derived. Finally, the implementation of the convolutional perfectly matched layer (CPML) for the proposed method is derived. At last, numerical results are given to verify the accuracy and efficiency of the proposed method.
关键词： leapfrog scheme,periodic structures,locally one-dimensional finite-difference time-domain (LOD-FDTD) method,unconditional stability
更新于2025-09-09 09:28:46
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[IEEE 2018 12th International Conference on Communications (COMM) - Bucharest (2018.6.14-2018.6.16)] 2018 International Conference on Communications (COMM) - Applications of a Frequency Selective Surface Based on a Combination of a Jerusalem Cross and a Circular Ring
摘要： Screening applications of a frequency selective surface (FSS) built on a FR4 substrate with two metal periodic patterns are reported. The square shaped unit cell contains a Jerusalem Cross (Jcross) metal pattern on one face and a circular ring one on the other. Broadband, X band and WLAN filters are proposed and assessed for TE and TM plane wave incidence up to an angle of 45o. The operation of the FSS is demonstrated by computer simulation. Two commercial solvers are used to verify the consistency of the results.
关键词： periodic structures,electromagnetic screening,filtering,Frequency Selective Surface
更新于2025-09-09 09:28:46
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Two-Dimensional Periodic Leaky-Wave Antenna for Oblique Frequency Scanning
摘要： A design of two-dimensional (2D) periodic leaky-wave antenna (P-LWA) to achieve an oblique frequency scanning is presented. This property allows for the antenna to independently scan in two distinct planes using opposite ports. The proposed antenna consists in an array of one-dimensional (1D) P-LWAs terminated by a series feeding line, where the former provides to radiation and scanning in the axis of the 1D P-LWAs and the later provides to scanning in the perpendicular direction. The combined unit cell has four ports, which allows in addition to the oblique frequency scanning in two orthogonal planes scanning with a linearly-polarized pencil beams. The proposed design of the 2D P-LWA is validated via full-wave simulation.
关键词： periodic structures,oblique scanning,frequency scanning,leaky-wave antenna,pencil beam
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Miniaturized Spoof Surface Plasmon Polaritons Transmission Line
摘要： Based on via arrays, a novel miniaturized spoof surface plasmon polaritons (SSPPs) transmission line (TL) with enhanced slow wave effect is proposed in this paper. The proposed miniaturized SSPPs TL is a bilateral metal structure connected by via arrays, composed of a pair of low impedance slotlines, a pair of flaring transitions and a section of corrugated metal strip. Excited by low impedance slotline, the bilateral structure transmits SSPPs from 2 GHz to 10 GHz and obtains a strong slow wave effect. In this paper, the designed structure and sample fabrication are presented. Simulated and measured S-parameters match well. High transmission efficiency and the enhanced slow wave effect are obtained. Moreover, the proposed structure halves the size compared to conventional planar SSPPs TLs excited by coplanar waveguide. These features give important potentials to develop integrated SSPPs devices and slow wave circuits.
关键词： periodic structures,surface waves,miniaturization
更新于2025-09-04 15:30:14