Tuntrakool, Sunti

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Tuntrakool, Sunti
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Tuntrakool, S.
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sunti.tu@kmitl.ac.th

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    Broadband Reflective Metasurface at X-band Frequency Using Snowflakes Fractal Ring Design
    (2025-01-01)
    Yaziz, Nur Syahirah Mohd
    ;
    Rahim, Mohamad Kamal A.
    ;
    Samsuri, Noor Asmawati
    ;
    Zubir, Farid
    ;
    Tuntrakool, Sunti
    A broadband reflective metasurface has been designed to integrate inward and outward fractal Koch rings operating at X-band frequencies. The integration between the inward and outward fractal Koch ring creates the snowflake fractal shape that operates at a center frequency of 10 GHz. Based on the simulated results, the reflection values are 0.9 with the reflection phase of 1800 which is between 900 to -900. Overall, all resonance frequencies exhibit more than 90% reflected power, with bandwidth of 1.90 GHz that cover from 8.70 GHz to 10.60 GHz.
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    Dual-Band Reflective Metasurfaces for 5G mmWave Applications: Design, Analysis, and Waveguide Validations
    (2026-01-01)
    Mohammed, Sunusi Garba
    ;
    Samsuri, Noor Asmawati Binti
    ;
    Rahim, Mohamad Kamal B.A.
    ;
    Ripin, Nabilah Binti
    ;
    Taufiqqurrachman
    This paper presents a dual-band reflective metasurface unit cell for millimeter-wave RIS applications operating at 26 GHz and 28 GHz, covering the 5G n258 and n257 bands. The proposed design features a hybrid resonator structure to achieve a consistent phase trend and strong reflection performance across the 5G mmWave frequency band. To ensure stable dual-band performance of the unit cell, parametric optimization is conducted. The unit cell is investigated through Floquet simulations and WR-34 rectangular -to-square waveguide-transition-based full-wave simulations, followed by experimental validation using a fabricated WR-34 rectangular-to-square waveguide transition. The simulated resonances at 26 GHz and 28 GHz are experimentally observed at 26.7 GHz and 28.9 GHz, respectively, indicating minor frequency deviations. Measured results demonstrate reflection magnitudes of -1.80 dB at 26.7 GHz and -0.80 dB at 28.9 GHz, with corresponding phase responses of - 68° and -13°, and bandwidths of 5.12% and 6.07%, respectively.
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    Geometry-Driven Performance of Unit Cells in Multiband Reflective Metasurfaces: A Comparative Study
    (2025-01-01)
    Taufiqqurrachman
    ;
    Rahim, Mohamad Kamal B.A.
    ;
    Samsuri, Noor Asmawati Binti
    ;
    Wijayanto, Yusuf Nur
    ;
    Yaziz, Nur Syahirah Mohd
    A multiband reflective metasurface can be designed using a multi-ring resonator, where the resonator can take various shapes such as circular, square, hexagonal, triangular, and others. This paper presents a comparative study of unit-cell multiband reflective metasurfaces based on their geometric structure, focusing on reflection magnitude, reflection phase, and bandwidth performance of hexagonal and triangular shapes. Both proposed designs are designed and simulated at X-band frequencies using an F4BMX220 substrate with a thickness of 1.5 mm. Simulation results show that the hexagonal shape offers better reflection performance and a wider bandwidth compared to the triangular shape.
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    Comparison between Snowflake Fractal and Koch Fractal for Intelligent Reflecting Surface
    (2025-01-01)
    Yaziz, Nur Syahirah Mohd
    ;
    Rahim, Mohamad Kamal A.
    ;
    Samsuri, Noor Asmawati
    ;
    Zubir, Farid
    ;
    Tuntrakool, Sunti
    This paper compares two fractal metasurface designs for Intelligent Reflecting Surfaces at X-band which is with a snowflake-shaped fractal ring and a fractal Koch metasurface. The snowflake ring design with a 10GHz center frequency achieves very high reflectance (~90%) at resonance and a bandwidth of about 1.90 GHz. The Koch-fractal design response with a bandwidth of 2.10 GHz at a center frequency of 10GHz. The method for both fractal metasurfaces and a comparable on their reflection coefficients, phase behaviour, bandwidth and current distributions are discussed in section II and section III.