arXiv subjects

Somayeh Komeylian

Publications and source records attributed to Somayeh Komeylian.

5 recordsLinked to original sources

arXiv2026

Comparative Performance of Graphene-Enabled Transmitarray Antenna and Reflectors for Wide-Angle Terahertz Beam Steering

This work compares a hemispherical graphene-based transmitarray antenna with its planar reflector counterpart for wide-angle beam steering in the THz regime. The theoretical framework of the planar reflector is formulated and numerically evaluated, yielding an elevation beam-steering range of \pm60{\deg}. In contrast, the transmitarray extends the elevation steering range to \pm78{\deg} while maintaining full 360{\deg} azimuthal coverage. The planar reflector exhibits a larger HPBW variation of 26.48{\deg}, compared with 13.1{\deg} for the transmitarray, resulting in a broader reflected-beam distribution and reduced directional power density, directivity, and gain. Meanwhile, the transmitarray maintains a more stable and controllable beamwidth response with greater directional power concentration over a wide steering range. The performance advantages of the transmitarray are demonstrated through comparisons with experimental results reported in the literature for planar reflectors and antennas. We further provide a comprehensive assessment of the performance advantages of the transmitarray over planar configurations across the remaining metrics.

cs.NI↗

arXiv2026

Active Hemispherical Metasurface Transmitarray Antenna for Wide-Angle 3D Beam Steering and Target Tracking

A stacked multilayer hemispherical graphene-based transmitarray antenna operating at 250 GHz is developed to achieve wide-angle 3D beam steering. This work presents the first fully automated CST Studio Suite macro for constructing the multilayer hemispherical geometry and configuring 121 independently tunable graphene sectors. Numerical results confirm that the integration of voltage-controlled graphene sectors with FCC gold patches enables wide-angle beam steering, achieving an elevation scanning range of -78{\deg} to 78{\deg} in {\theta} and full 360{\deg} azimuthal coverage while maintaining stable radiation characteristics and broadband impedance matching (|S11| < -10 dB) with a relative bandwidth of 40%. The antenna achieves a directivity range of 11.38 - 14.72 dBi and an SLL range of -6.8 to -9.8 dB across all investigated steering directions. It also maintains high antenna efficiencies from 71% to 80% with a 5% degradation due to imperfections across the entire scanning range, making it a promising candidate in practical moving-target-tracking applications.

cs.NI↗

arXiv2026

Graphene-based Hemispherical Transmitarray Antenna for Wide-Angle Beam Steering and Ultrafast Moving Target Tracking

This work expands the application of dynamically tunable graphene to implement a hemispherical transmitarray antenna tailored for wide-angle electronic beam steering and ultrafast moving-target tracking at 250 GHz. The proposed hemispherical transmitarray antenna features a dynamically reconfigurable graphene-based multilayer configuration consisting of gold radiating patches, biased graphene sectors, hBN dielectric layers, and a centrally positioned hornfeed. The analytical framework of graphene-based reconfigurable metasurfaces including graphene surface-conductivity modeling, voltage-controlled surface impedance, transmission-coefficient, and conformal array-factor analysis, has been established for hemispherical transmitarray antenna for the first time. Moreover, the analytical and practical mapping between desired beam directions and the corresponding graphene bias voltages have been developed for the transmitarray antenna for the first time. Our transmitarray antenna possesses exceptional 3D beamsteering, providing wide-angle elevation scanning from -87 degrees to 87 degrees and full 360-degree azimuthal coverage. It also exhibits an antenna efficiency ranging from 68% to 80% with a 10% degradation.

cs.NI↗

arXiv2022

Implementation of the Digital QS-SVM-based Beamformer on an FPGA Platform

To address practical challenges in establishing and maintaining robust wireless connectivity such as multi-path effects, low latency, size reduction, and high data rate, the digital beamformer is performed by the hybrid antenna array at the frequency of operation of 10 GHz. The proposed digital beamformer, as a spatial filter, is capable of performing Direction of Arrival (DOA) estimation and beamforming. The most well-established machine learning technique of support vector machine (SVM) for the DoA estimation is limited to problems with linearly-separable datasets. To overcome the aforementioned constraint, in the proposed beamformer, the QS-SVM classifier with a small regularizer has been used for the DoA estimation in addition to the two beamforming techniques of LCMV and MVDR. The QS-SVM-based beamformer has been deployed in an FPGA board, as demonstrated in detail in this work. The implementation results have verified the strong performance of the QS-SVM-based beamformer in suppressing undesired signals, deep nulls with powers less than -10 dB in undesired signals, and transferring desired signals. Furthermore, we have demonstrated that the performance of the QS-SVM-based beamformer consists of other advantages of average latency time in the order of milliseconds, performance efficiency of more than 90\%, and throughput of about 100\%.

cs.NI↗

arXiv2022

Implementation of a Three-class Classification LS-SVM Model for the Hybrid Antenna Array with Bowtie Elements in the Adaptive Beamforming Application

To address three significant challenges of massive wireless communications including propagation loss, long-distance transmission, and channel fading, we aim at establishing the hybrid antenna array with bowtie elements in a compact size for beamforming applications. In this work we rigorously demonstrate that bowtie elements allow for a significant improvement in the beamforming performance of the hybrid antenna array compared to not only other available antenna arrays, but also its geometrical counterpart with dipole elements. We have achieved a greater than 15 dB increase in SINR values, a greater than 20% improvement in the antenna efficiency, a significant enhancement in the DoA estimation, and 20 increments in the directivity for the hybrid antenna array with bowtie elements, compared to its geometrical counterpart, by performing a three-class classification LS-SVM (LeastSquares Support Vector Machine) optimization method. The proposed hybrid antenna array has shown a 3D uniform directivity, which is accompanied by its superior performance in the 3D uniform beam-scanning capability. The directivities remain almost constant at 40.83 dBi with the variation of angle {\theta}, and 41.21 dBi with the variation of angle {\phi}. The unrivaled functionality and performance of the hybrid antenna array with bowtie elements makes it a potential candidate for beamforming applications in massive wireless communications.

cs.LG↗