Sakonkanapong, Arnon
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Item type:Publication, Broadband circularly polarized microstrip patch antenna using circular artificial ground structure and meandering probe(2020-01-01); ; Fukusako, TakeshiTo enhance axial ratio (AR) bandwidth, this research proposes a circularly polarized (CP) single-fed microstrip patch antenna using a circular artificial ground structure (AGS) and meandering probe. To achieve broader AR bandwidth, the circular AGS is populated with rectangular unit cells and partially cut unit cells along the circular contour, while the meandering probe is used to improve the impedance bandwidth. Simulations are performed and results compared with that of conventional rectangular-AGS antenna. The simulation results show that the circular-AGS antenna, given 62 mm circular ground plane, achieves broader impedance (5.12 - 9.00 GHz and 54%), AR (5.21 - 8.27 GHz and 45%) and gain bandwidths (3.85 - 7.00 GHz and 58.06%), in comparison with the rectangular-AGS antenna (4.50 - 7.45 GHz and 49%; 4.52 - 7.42 GHz and 21%; and 4.00 - 6.80 GHz and 51.58% for impedance, AR and gain bandwidths). The circular-AGS antenna is capable of converting linear polarization in the off-axial ratio band into circular polarization. To verify, a circular-AGS antenna prototype is fabricated and experiments undertaken. The experimental impedance, AR and gain bandwidths of the circular-AGS antenna are 47.82% (5.17 - 8.42 GHz), 43.81% (5.24 - 8.17 GHz) and 60.74% (3.75 - 7.00 GHz). The proposed circular-AGS antenna can achieve broader AR bandwidth and is thus ideal for broadband CP applications. The novelty of this research lies in the use of circular AGS to effectively enhance AR bandwidth, as opposed to rectangular AGS which is conventionally used in CP polarizers. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Numerical analysis of heat transfer and tissue deformation in liver cancer during microwave ablation: A comparison of bioheat and porous media models(2025-08-01); Rattanadecho, PhadungsakThis study presents a numerical comparison of microwave ablation using the Pennes bioheat and porous media models in a deformed liver cancer geometry. A single slot coaxial antenna operating at 2.45 GHz with a power of 10 W for 10 min was simulated using the finite element method, incorporating electromagnetic wave propagation, heat transfer, and tissue deformation. Validation against published experimental data and a mesh independence test confirmed the accuracy of the model. Results indicate up to a 6.7 % higher specific absorption rate in the porous media approach, contributing to a temperature difference of approximately 10–13 % at 10 min compared to the Pennes model. Peak von Mises stress increased by more than 2 Pa in tumor regions, and necrosis progression differed between the models. While both models predicted complete tumor cell death, the Pennes bioheat approach consistently reached thresholds sooner in both tumor and adjacent healthy tissue. These findings highlight the role of tissue porosity and convection in heat transport and deformation, demonstrating the porous media model's improved predictive capability for longer ablation durations and its potential for optimizing treatment protocols. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Near-Field HF-RFID and CMA-Based Circularly Polarized Far-Field UHF-RFID Integrated Tag Antenna(2020-01-01); This research proposes an integrated high-frequency (HF) and ultrahigh-frequency (UHF) passive radio frequency identification (RFID) tag antenna for near-field (13.56 MHz) and far-field (920-925 MHz) communication. This tag antenna is advantageous for the applications with lossy material in the near-field communication and mitigates polarization loss in the far-field communications. The HF-RFID tag antenna is of square spiral structure, and the circularly polarized UHF-RFID structure consists of a square loop radiator with cascading loop feeding and shorted stub. The structure of HF-RFID tag antenna situated inside the circularly polarized UHF-RFID tag can avoid the significant effect of the near-field magnetic coupling from the square loop. The UHF-RFID tag antenna is realized by using characteristic mode analysis for wideband circular polarization. The HF-RFID structure is conjugate-matched with NXP NT3H2111 chip, and the UHF-RFID structure is conjugate-matched with NXP G2X chip. Simulations were carried out, and an antenna prototype was fabricated. The experimental results reveal that the radiation pattern of UHF-RFID tag antenna is bidirectional with a gain of 0.31 dBic. The impedance bandwidth covers the frequency range of 903-944 MHz, and the axial ratio in boresight direction at 922.5 MHz is 1.67 dB, with the axial ratio bandwidth over 863-938 MHz. The maximum near-field and far-field reading ranges are 4.9 cm and 8.7 m. The proposed integrated dual-band passive tag antenna is operationally ideal for HF-RFID and UHF-RFID applications. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Elliptical ring antenna excited by circular disc monopole for UWB communications(2020-01-01); This research proposes a compact elliptical ring antenna excited by a circular disc monopole (CDM) for ultra-wideband (UWB) communications. In the study, time- and frequency-domain pulse distortions of the antenna in the transmission mode were characterized by magnitude and phase of the antenna transfer function (H<inf>rad</inf>). The results showed that the gain and magnitude of H<inf>rad</inf> in the boresight direction are sufficiently flat with linear phase response. The average antenna gain is 3.9 dBi over the UWB spectrum. The antenna also exhibits low pulse distortion with the correlation factors (ρ) of 0.98 and 0.93 for the fifth-order derivative Gaussian pulse and modulated Gaussian pulse with 6 GHz band rejection. The CDM-excited elliptical ring antenna possesses several attractive features, including wide bandwidth, flat gain, compactness, low cost, and low distortion.