Amir Djalalian-Assl
Here I report on comparisons between two different techniques in fabricating arrays of subwavelength cross-shaped apertures in metallic screens. The aim was to determine the most appropriate fabrication technique to be used considering the cost, ease of fabrication and accuracy in which the apertures were created. Some interesting physical effects are observed.
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In this paper, we present the design procedure of modulated metasurface leaky-wave antennas (MMLWAs) to generate coaxial superposition of vortex beams with several orbital angular momentum (OAM) states. Based on the Flat Optics (FO) technique and aperture field estimation (AFE) method, an analytical framework is proposed to facilitate the implementation of MMLWAs generating multiple topological charges in the OAM regimen. Furthermore, using the spectral analysis which has been derived from the proposed model, we have shown that the symmetry of aperture shape can affect the purity of the mode. …
Miniature varifocal lenses are crucial for many applications requiring compact optical systems. Here, utilizing electro-mechanically actuated 0.5-mm aperture infrared Alvarez meta-optics, we demonstrate 3.1 mm (200 diopters) focal length tuning with an actuation voltage below 40 V. This constitutes the largest focal length tuning in any low-power electro-mechanically actuated meta-optic, enabled by the high energy density in comb-drive actuators producing large displacements at relatively low voltage. The demonstrated device is produced by a novel nanofabrication process that accommodates meta…
We propose a feedback-assisted direct laser writing method to perform laser ablation of fiber optics devices in which their light-collection signal is used to optimize their properties. A femtosecond-pulsed laser beam is used to ablate a metal coating deposited around a tapered optical fiber, employed to show the suitability of the approach to pattern devices with small radius of curvature. During processing, the same pulses generate two-photon fluorescence in the surrounding environment and the signal is monitored to identify different patterning regimes over time through spectral analysis. T…
Tri-band Aperture-shared Antenna Array Using Scalable FSS-based Electromagnetic Transparent Structure
针对三频带孔径共享阵列中低频偶极子屏蔽导致中高频辐射恶化的问题，提出一种基于可扩展FSS的双频带电磁透明结构，用于构建低频偶极子，实现0.65-0.88/1.92-2.18/3.3-3.8 GHz三频带共享，且中高频增益偏差小于0.6 dB。
A Tri-Band Shared-Aperture Base Station Antenna Array Covering 5G Mid-Band and 6G Centimetric Wave Band
本文提出一种三频共享孔径天线阵列，覆盖5G中频带和6G厘米波频段，通过分段螺旋辐射器和谐振器实现宽频段低反射和高隔离性能。
A Wideband Tri-Band Shared-Aperture Antenna Array for 5G and 6G Applications
本文提出了一种宽频三频共享孔径天线阵列，通过分段螺旋辐射器和磁电偶极子结构，实现了对5G和6G频段的高效覆盖与低雷达截面性能。
In this paper, the design, realization, and demonstration of a broadband millimeter-wave imaging system based on the synthetic aperture radar technique (SAR) are discussed. The proposed system, operating within the frequency range of 25.3-30.8 GHz, consists of a tapered slot antenna as the transmitter and two half-circle antennas as the receivers. The size of the antenna is 19.5 * 8 mm with a maximum gain of 8.5 dB. The transmitter and the receiver antennas are printed on the same board. This feature leads to a highly compact and flexible configuration, enabling the applicability of the propos…
We present the design and fabrication of 3D printed holographic beamforming antennas. The antennas utilize additively manufactured hollow rectangular waveguides that feed radiating rectilinear slots inserted into the upper conducting wall. The lengths of the individual slots are altered to implement a holographic beamforming solution designed using a coupled dipole formalism. For rapid verification, the designed antennas are fabricated using a desktop dual-extrusion fused filament 3D printer. The body of each antenna and its inner conducting surface are respectively printed using polylactic ac…
A C-band microwave rectenna using aperture-coupled antenna array and novel Class-F rectifier with cavity
本文提出了一种基于 aperture-coupled 天线阵列和新型 Class-F 整流器的 C 频段 rectenna，实现了 72% 的微波到直流转换效率。
Numerical Investigation of a 3D End-Firing Antenna Array Based on Two-Photon Polymerization on Thin-Film Lithium Niobate for Optical Beam Steering
研究基于双光子聚合在薄膜铌酸锂上设计三维端射天线阵列用于光束转向，解决传统OPA设计权衡问题。通过提升聚合物天线实现二维光束转向并保持宽带优势，模拟展示高效传输及特定视场与波束宽度，为3D光子相控阵奠定基础。
We present the design, fabrication, and experimental characterization of a two-dimensional, dynamically tuned, metasurface aperture, emphasizing its potential performance in computational imaging applications. The dynamic metasurface aperture (DMA) consists of an irregular, planar cavity that feeds a multitude of tunable metamaterial elements, all fabricated in a compact, multilayer printed circuit board process. The design considerations for the metamaterial element as a tunable radiator, the associated biasing circuitry, as well as cavity parameters are examined and discussed. A sensing matr…
In this paper, we demonstrate a radiation-strength-chirped metasurface centimeter-long grating antenna, whose beam quality is approaching the diffraction limit in its footprint with 90 percent efficiency.Instead of chirping the duty cycle to tune radiation strength, which calls for non-scalable fabrication resolution, we design a 2D fish-bone surface grating with apodized width of the bone.The meta surface is made by silicon nitride on top of silicon waveguide to weakly perturb the mode. Moreover, a Monte Carlo Markov Chain(MCMC) algorithm is implemented to design the radiation strength profil…
We introduce and discuss a new approach to the phase retrieval of fields radiated by continuous aperture sources having a circular support, which is of interest in many applications including the detection of shape deformations on reflector antennas. The approach is based on a decomposition of the actual 2-D problem into a number of 1-D phase retrieval problems along diameters and concentric rings of the visible part of the spectrum. In particular, the 1-D problems are effectively solved by using the spectral factorization method, while discrimination arguments at the crossing points allows to…
Popup Arrays for Large Space-Borne Apertures
本文提出一种轻质柔性、可折叠卷曲并部署弹出的10GHz玻璃纤维复合材料偶极子阵列，验证其空间耐久性、电磁性能与可规模化制造能力。
This study presents a nonreciprocal-beam phased-array antenna constituted of phase-gradient patch radiators integrated with transistor-based nonreciprocal phase shifters. Such an antenna exhibits different beams for transmission and reception states. The proposed phased-array antenna provides power amplification for both transmission and reception states, which is of paramount importance in most practical applications. In addition, in contrast to the recently proposed time-modulated antennas, the proposed nonreciprocal-beam phased-array antenna introduces no undesired time harmonics and unwant…
Analysis, Design, and Fabrication of a High-Gain Low-Profile Metasurface Antenna Using Direct Feeding of Sievenpiper s HIS
本文提出并验证一种直接馈电 Sievenpiper HIS 单元的低剖面高增益 TMA，通过平行带状线简化结构，实现紧凑尺寸、0.77 口径效率及约 13.5 dBi 实测增益。
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