Tuntrakool, Sunti

Preferred name

Tuntrakool, Sunti

Alternative Name

Tuntrakool, S.

Main Affiliation

School of Industrial Education and Technology

sunti.tu@kmitl.ac.th

Now showing 1 - 7 of 7

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Polarization insensitive switchable metamaterial absorber/reflector for x-band applications
(2020-01-01)
Mustapha, M. G.
;
Rahim, M. K.A.
;
Murad, N. A.
;
Ayop, O.
;
Tuntrakool, S.
A unit cell of squared shaped polarization-insensitive switchable metamaterial absorber/reflector is presented. The structure operates at 10.20 GHz under both absorber mode and reflector mode configurations. Copper wire bridging the gaps to form a circular shape structure were used as switches for operation mode selections. The structure was designed on an FR4 substrate, and the incidental wave angles were varied from 0 to 50 degrees. The structure demonstrated almost 100% absorption at resonance, 3.314 GHz percentage bandwidth at 80% as an absorber. On the other hand, as reflector, it demonstrated almost a 90% reflection and a usable bandwidth of 3.327 GHz.
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UWB MIMO antenna design and analysis at millimetre wave frequencies
(2025-01-01)
Mohamad Nazer, Mohamad Aiman Hadi
;
Rahim, Mohamad Kamal A.
;
Murad, Noor Asniza
;
Samsuri, Noor Asmawati
;
Pramudita, Aloysius Adya
The Ultra-Wideband (UWB) antenna is widely used in radar systems due to its wide bandwidth and high diversity gain. However, UWB systems also experience challenges related to multipath fading. To address these issues, multiple-input-multiple-output (MIMO) technology has been introduced. To improve the performance of MIMO systems, it is essential for the elements within the MIMO antenna array to exhibit low correlation and high total efficiency. In this paper a design and simulation of a printed UWB antenna with additional MIMO implementation. The simulation results from three different MIMO configurations were systematically compared to assess their performance based on three parameters of MIMO: the Envelope Correlation Coefficient (ECC), Diversity Gain (DG), and Mean Effective Gain (MEG). In this proposal of the project, the evaluation of results is primarily cantered around the design of UWB antenna and analysis of the MIMO configurations.
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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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Integer- And fractional-order VCO using non-inertial amplitude stabilization and modern active elements
(2020-04-28)
Sotner, Roman
;
Petrzela, Jiri
;
Jerabek, Jan
;
Langhammer, Lukas
;
Polak, Josef
This paper introduces design of the linearly tunable quadrature voltage-controlled oscillator (VCO) using modern off-the-shelf active elements suitable for the design of electronically adjustable applications. The simplified topology was achieved using non-inertial stabilization of amplitude. It allows targeting adjustability of the oscillation frequency only into lossless integrator part of the topology. This arrangement simplifies the design and the tenability also. Derived symbolical expressions indicate that gain adjustment of used amplifiers (that are still in single path) does not influence amplitude and phase shift ratio of generated waveforms, which is a beneficial feature. The performances of the circuit are tested experimentally in band of units of MHz and results confirmed expected behavior. Initial study of the oscillator with fractional-order capacitors is presented and discussed. Results are supported by laboratory measurements.
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High input impedance voltage-mode universal filter and its modification as quadrature oscillator using VDDDAs
(2017-05-01)
Tuntrakool, Sunti
;
Kumngern, Montree
;
Sotner, Roman
;
Herencsar, Norbert
;
Suwanjan, Peerawut
The second order universal voltage-mode filter using voltage differencing differential difference amplifiers (VDDDAs) has been proposed. It has high input impedance voltage-mode biquad filter with orthogonal tune of natural frequency and quality factor. The proposed filter simultaneously provides five filter responses: low-pass (LP), high-pass (HP), band-reject (BR), all-pass (AP) and band-pass (BP) in the same circuit topology. The natural frequency and quality factor can be tuned electronically and orthogonally dc bias current. The output impedance at output nodes HP, AP and BR has low impedance which can connect to other circuit without the use of voltage buffers. The proposed filter consists of three VDDDAs, one grounded resistor and two grounded capacitors. This makes the proposed filter suitable for integrated circuit development. With slightly modifying the proposed filter, the voltage-mode qudrature sinusoidal oscillator with low output impedance and independent control of condition of oscillation (CO) and frequency of oscillation (FO) has been achieved. The results shown in this paper are from PSPICE simulation and experiment to validate the proposed circuits.
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Characterization of the koch fractal embedded hexagonal loop frequency selective surface structure for X-band application
(2020-11-01)
Mohamed Nafis, Nur Biha
;
Rahim, Mohamad Kamal A.
;
Ayop, Osman
;
Majid, Huda A.
;
Tuntrakool, Sunti
This paper presented the bandstop Koch fractal embedded hexagonal loop frequency selective surface (FSS) for the X-band application. The simulated transmission coefficient response () had been obtained by using CST software. The surface current distribution and the electric field density are illustrated to explain in detail the of the fractal based FSS structure. The proposed structure is highly insensitive towards angular stability and also polarization independent up to . The parametric analysis on the effect of the periodicity, width, and height of the fractal FSS structure on the has been illustrated and discussed thoroughly.
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Illuminance sensing in agriculture applications based on infra-red short-range compact transmitter using 0.35 μm CMOS active device
(2020-01-01)
Sotner, Roman
;
Jerabek, Jan
;
Polak, Ladislav
;
Petrzela, Jiri
;
Jaikla, Winai
This paper introduces a novel electronic system for simplex low-bitrate infra-red (IR) communication applications. The transmitter is implemented completely by analog building blocks, formed with the help of a recently fabricated chip that includes active elements allowing various modular interconnections. For the design of this chip, the ON Semiconductor C035~0.35μm I3T25 technology was chosen due to the trade-off between cost, efficiency and obtainable parameters. The designed transmitter operates as a voltage-to-duty cycle converter, using pulse width modulation that causes ON/OFF keying of the carrier signal for infra-red (IR) diode. The duty cycle variable between 7% and 83% is modulated by the input voltage (in the range of ±0.8 V) of the transmitter. The use case of the proposed concept in the measurement of illuminance within the range of 30 lx and 550 lx is also presented. The quality of the transmission was evaluated as the error between the transmitted and received values of the duty cycle (kept mostly below 10 %). The maximal power consumption of the transmitter reaches 180 mW.
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Tuntrakool, Sunti

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