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    A triple-band printed microwave absorber for WLAN/WiMAX applications
    (2017-10-19)
    Khoomwong, E.
    ;
    Soemphol, C.
    ;
    Phongcharoenpanich, C.
    This paper presents a triple-band printed-circuitboard microwave absorber for applications in 2.4GHz WLAN and 3.5/5.8GHz WiMAX bands. The absorber consists of simple geometries with tuning elements and chamfering, which can significantly reduce the modeling errors. The study and design processes are based on numerical simulations. The simulated results show the absorption bandwidths (at 50%) of 160MHz (2.36-2.52GHz), 160MHz (3.48-3.64GHz) and 520MHz (5.54- 6.06GHz). The absorptions at the center frequency of each band (i.e. 2.45, 3.55 and 5.78GHz) are also found feasible at 97.6%, 85.2% and 96.0%, respectively. From the study, the proposed absorber is applicable for a fairly wide-Angle of wave incidence and suitable for a number of applications in the specified bands. The main advantages of the proposed absorber are thin, simple and low-cost structure, which can be very useful for various applications in WLAN and WiMAX bands.
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    Dual-band conical-beam antenna using 3D monopole with symmetrical slot on the ground plane
    (2011-11-07)
    Phongcharoenpanich, C.
    ;
    Khoomwong, E.
    In this paper, the utilization of a conducting spherical monopole radiator as a dual-band conical-beam antenna is investigated. The multi-band property is achieved by adding a quarter-wavelength slot (stub) and a conducting cylindrical ring for matching and bandwidth enhancement of the second operating band. The design is investigated and summarized based on numerical experiments or simulations. It is found that the proposed antenna provides a conical-beam with the impedance bandwidths (S11 less than 10 dB) covering two bands of operating frequencies, 2.4 to 2.5 GHz and 5.15 to 5.825 GHz. The best-matched values of S11 are about 21 and 16 dB for the first and second operating bands, respectively. Gains of the antenna are reasonably applicable, about 3.1 and 7.1 dBi at the centers of the two operating bands above. The far-field radiation patterns are of conical-beam type as required, with the main beams directed at the same 45-degree elevation angle for both operating bands. A prototype antenna has been successfully fabricated and most of the experimental results are agreed well with ones from the simulations. The investigation of this antenna also guides us that a quarter-wavelength slot may be further applied for other multi-band applications. © 2011 IEEE.
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    Dual-band conical-beam antenna for IEEE 802.11 a/b/g applications
    (2010-12-01)
    Phongcharoenpanich, C.
    ;
    Khoomwong, E.
    In this paper, the utilization of a conducting spherical monopole radiator as a dual-band conical-beam antenna is investigated. The multi-band property is achieved by adding a quarter-wavelength slot (stub) and a conducting cylindrical ring for matching and bandwidth enhancement of the second operating band. The design is investigated and summarized based on numerical experiments or simulations. It is found that the proposed antenna provides a conical-beam with the impedance bandwidths (S11 less than -10 dB) covering two bands of operating frequencies, 2.4 to 2.5 GHz and 5.15 to 5.825 GHz. The best-matched values of S11 are about -21 and -16 dB for the first and second operating bands, respectively. Gains of the antenna are reasonably applicable, about 3.1 and 7.1 dBi at the centers of the two operating bands above. The far-field radiation patterns are of conical-beam type as required, with the main beams directed at the same 45-degree elevation angle for both operating bands. A prototype antenna has been successfully fabricated and most of the experimental results are agreed well with ones from the simulations. The investigation of this antenna also guides us that a quarter-wavelength slot may be further applied for other multi-band applications. © 2010 IEICE Institute of Electronics Informati.
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    Simulations of em fields inside the concentric conducting spherical cavity using the FD-TD in spherical coordinates
    (2000-01-01)
    Phongcharoenpanich, C.
    ;
    Khoomwong, E.
    ;
    Krairiksh, M.
    The finite-difference time-domain (FD-TD) method in spherical coordinates is introduced and utilized to simulate electromagnetic fields inside a concentric conducting spherical cavity. A stability criterion and analysis are also presented. Finally, some numerical results of mode patterns inside the cavity are illustrated and compared with analytical solutions.