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Measurement of Radiated Field from Transmitting Antennas Located in Various Environments
(2019-04-01)
Krairiksh, Monai
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Kittiyanpunya, Chainarong
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Limpiti, Thunyawat
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Tantisopharak, Tanawut
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Leekul, Prapan
In microcellular communications, the transmitting antennas can be installed at low heights above the ground. However, even for low elevation towers, installation cost is still high. One of the possible ways for the deployment of base station antennas is to install them near the ground in order to do away with the tower. The main purpose of this paper is to suggest installation of the radiating antennas near the ground and tilting their orientation toward the sky - a totally nonintuitive solution. It will be shown that such deployments have the potential of reducing slow fading and can further enhance the signal strength close to the radiating antenna. This paper provides measured data for the received fields to validate the theoretical conjecture of such a deployment in various environments. The measured results are presented for 245, 800, 1000, and 2400 MHz. It is illustrated that such an unorthodox deployment can result in a low cost for the installation of base station antenna as the towers are not necessary. This can be useful in restoring communications in emergency situations where minimum infrastructure exists.
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Sub-30 ppm/oC high-frequency temperature-compensated CMOS relaxation oscillator
(2018-07-02)
Sakphrom, Siraporn
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Limpiti, Thunyawat
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Wichaipanich, Noraset
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Thanachayanont, Apinunt
This paper describes the design and realization of a high-frequency temperature-compensated CMOS relaxation oscillator in a 0.35-µm CMOS technology. The proposed oscillator employs the current-controlled topology with a resistive source-degeneration transconductor and a current comparator in order to achieve high oscillation frequency and low power dissipation. Temperature compensation of the oscillation frequency is achieved by simulation results show that, at a nominal oscillation frequency of 32.48 MHz, the proposed oscillator exhibited a temperature coefficient of less than 28.41 ppm/oC over a temperature range of -40oC to +120oC, while consuming 241.5 µW from a 2.5-V single power supply voltage.
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In situ moisture content monitoring sensor detecting mutual coupling magnitude between parallel and perpendicular dipole antennas
(2012-03-06)
Limpiti, Thunyawat
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Krairiksh, Monai
This paper presents an in situ moisture content sensor based on a switched-polarization dipole antenna that detects the magnitude of mutual coupling between perpendicular and parallel polarizations. Three aspects of the sensor development are presented: a new closed-form calculation of mutual impedance of perpendicular polarization dipole antenna, an antenna design, and an investigation of performance enhancement. As the sensor detects only the magnitude of mutual coupling, it is low cost and low profile and needs less processing time. Thus, it is suitable for a closed-loop drying system. Our study has shown that the values of the dielectric constants measured by this sensor are comparable to the reference values from the transmission line technique in the previous work. However, there are significant differences in the values of the dielectric loss factors because the structure of the presented sensor is not a closed boundary like the transmission line sensor. Therefore, error compensation has been developed to correct the results. This sensor, in a closed-loop drying system, has shown good performance for in situ monitoring and real-time monitoring. Consequently, it is very suitable for monitoring the moisture content of paddy (rough rice). © 1963-2012 IEEE.
1
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A portable dielectric-property determination system using coupled antennas
(2008-11-06)
Mearnchu, Jhirat
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Limpiti, Thunyawat
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Torrungrueng, Danai
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Akkaraekthalin, Prayoot
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Krairiksh, Monai
This paper presents a dielectric-property determination system that measures magnitude of reflection and coupling coefficients of coupled antennas. They are plotted on a ε<inf>r</inf>′ ε<inf>r</inf>″ plane, and the intersection of these two quantities provides the value of ε<inf>r</inf>′ and ε<inf>r</inf>″. Measurement results of paddy validate the effectiveness of the proposed technique. The system provides accurate results. The error from the results of proposed system differs from the use of network analyzer of less than 4 %.
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Dielectric-property determination from measurement of magnitude of reflection and coupling coefficients of coupled antennas
(2008-10-06)
Mearnchu, Jhirat
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Limpiti, Thunyawat
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Torrungrueng, Danai
;
Akkaraekthalin, Prayoot
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Krairiksh, Monai
This paper presents a dielectric-property determination technique that measures the magnitudes of the reflection and coupling coefficients of coupled antennas. They are plotted on the ε′<inf>r</inf> ε″ <inf>r</inf> plane, and the intersection of these two quantities provides the values of ε′<inf>r</inf> and ε″<inf>r</inf> where ε′<inf>r</inf> is the real part and ε″<inf>r</inf> is the imaginary part of the relative complex permittivity. Measurement results of water validate the effectiveness of the proposed technique. This technique provides a compact measurement system and is suitable for localized dielectric determination. ©2008 IEEE.

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