• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.155-161
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• 2007

This paper presents the design simulation, implementation, and measurement of a miniaturized PCS / Satellite DMB dual-band stacked mompole antenna with a parasitic patch for mobile communication terminals. A stacked helix is realized by using a via hole with height of 0.4 mm and a diameter of 0.35 mm to connect upper- and lower-layer helix sections for a reduction of the dimensions of the antenna. In addition the stacked helix chip antenna is interleaved with a parasitic patch to achieve two different radiation modes. The ratio of the first frequency and the second frequency vary with the geometrical parameter of the parasitic patch. The fabricated antenna uses FR-4 substrate with a relative permittivity of 4.2. Its dimensions are $15.5{\times}7.6{\times}0.4 mm^3$. The measured impedance bandwidths (VSWR<2) are 240 and 250 MHz at the operating frequencies, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.123-130
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• 2016

In this paper, a novel flexible microfluidic metamaterial absorber is proposed for remote chemical sensor applications. The proposed metamaterial absorber consists of a periodic of split-ring-cross resonators(SRCRs) and a microfluidic channel. The SRCR patterns are inkjet-printed using silver nanoparticle inks on paper. The microfluidic channels are laser-etched on polydimethylsiloxane(PDMS) material. The proposed absorber can detect change of the effective permittivity at different liquids. Therefore, the absorber can be used for a remote chemical sensor by detecting change of the resonant frequencies. The performance of the proposed absorber is demonstrated with full-wave simulation and measurement results. The experimental results shows that the resonant frequency is 10.49 GHz at the empty channel. When ethanol and DI-water are injected into the channel, the resonant frequencies are 10.04 GHz and 8.9 GHz, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.179-186
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• 2008

Probing inside of concrete structures is one of the important steps in assessing condition of the structure. For the assessment, electromagnetic induction method and electromagnetic wave method are currently applied to the measurement of cover depth, and the detection of reinforcement embedded in concrete. To determine detection capability of locating reinforcement embedded in concrete, commercially available nondestructive testing (NDT) equipments have been tested. The equipments include electromagnetic wave system and electromagnetic induction system. In the tests, nine concrete specimens which have the dimensions of 1,000mm(length))${\times}$300mm(width) with thickness varying from 125mm to 150mm are used. The reinforcement are located at 45, 60, 100mm depth from the concrete surface. Horizontal reinforcement spacing has been set over 100mm. From the outcome, it is shown that error is increased as the diameter of reinforcement enlarge in case of using electromagnetic induction method. In case of using electromagnetic wave method, the detection of reinforcement embedded in deep is good in the view of reliability because of using the relative permittivity on the real cover depth.

• Journal of Radiation Protection and Research
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• v.41 no.2
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• pp.167-171
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• 2016

Background: TlBr is of considerable technological importance for radiation detection applications where detecting high-energy photons such as X-rays and ${\gamma}$-rays are of prime importance. However, there were few reports on investigating optical properties of TlBr itself for deeper understandings of this material and for making better radiation detection devices. Thus, in this paper, we report on the optical characterizations of TlBr single crystals. Spectroscopic ellipsometry (SE) and photoluminescence (PL) measurements at RT were performed for this work. Materials and Methods: A 2-inch TlBr single crystalline ingot was grown by using the vertical Bridgman furnace. SE measurements were performed at RT within the photon energy range from 1.1 to 6.5 eV. PL measurements were performed at RT by using a home-made PL system equipped with a 266 nm-laser and a spectrometer. Results and Discussion: Dielectric responses from SE analysis were shown to be slightly different among the different samples possibly due to the different structural/optical properties. Also from the PL measurements, it was observed that the peak intensities of the middle samples were significantly higher than those of the other two samples. With the given values for permittivity of free space (${\varepsilon}_0=8.854{\times}10^{-12}F{\cdot}m^{-1}$), thickness (d = 1 mm), and area ($A=10{\times}10mm^2$) of the TlBr sample, capacitances of TlBr were 6.9 pF (at $h{\nu}=3eV$) and 4.4 pF (at $h{\nu}=6eV$), respectively. Conclusion: SE and PL measurement and analysis were performed to characterize TlBr samples from the optical perspective. It was observed that dielectric responses of different TlBr samples were slightly different due to the different material properties. PL measurements showed that the middle sample exhibited much stronger PL emission peaks due to the better material quality. From the SE analysis, optical, dielectric constants were extracted, and calculated capacitances were in the few pF range.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.290-298
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• 2018

Herein, an S-band internally-matched power amplifier that shows a power capability of 300 W in a Long Term Evolution(LTE) band 7 is designed and fabricated using a CGHV40320D GaN HEMT from Wolfspeed. Based on the nonlinear model, the optimum source and load impedance are extracted from the source-pull and load-pull simulations at the fundamental and harmonic frequencies, and the harmonic impedance tuning circuits are implemented inside a ceramic package. The internally matched power amplifier, which is fabricated using a thin-film substrate with a high relative permittivity of 40 and an RF35TC PCB substrate, is measured at the pulsed condition with a pulse period of 1 ms and a duty cycle of 10%. The measured results show a maximum output power of 257~323 W, a drain efficiency of 64~71%, and a power gain of 11.5~14.0 dB at 2.62~2.69 GHz. The LTE-based measurement shows a drain efficiency of 42~49% and an ACLR of less than -30 dBc(excluding 2.62 GHz) at an average power of 79 W.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.5
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• pp.301-313
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• 2021

Theoretical background for the meaning of various piezoelectric properties can be easily found in a number of textbooks and academic papers. In contrast, how they are actually measured and characterized are rarely described, though this information would be the most important especially to the researchers who just started working on the field. It follows that this report was intended to provide a practical guidance for measuring basic but essential properties of ferroelectric-based piezoelectric materials. The discussion begins with how to measurement dielectric properties such as dielectric permittivity and loss (dissipation factor), followed by piezoelectric properties such as piezoelectric constants, electromechanical coupling factor, and quality factor as well as ferroelectric features, i.e., electric field dependent polarization hysteresis. Though our discussion here is limited to the techniques that are already well-standardized, it is expected to make a seed to be developed into more challenging and creative ones.

• Composites Research
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• v.35 no.3
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• pp.201-215
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• 2022

This paper presents the development of thin and lightweight ultra-high temperature radar-absorbing ceramic composites composed of an aluminosilicate ceramic matrix-based geopolymer reinforced ceramic fiber and sendust magnetic nanoparticles in X-band frequency range (8.2~12.4 GHz). The dielectric properties with regard to complex permittivity of ceramic/sendust-aluminosilicate composites were proportional to the size of sendust magnetic nanoparticle with high magnetic characteristic properties as flake shape and its concentrations in the target frequency range. The characteristic microstructures, element composition, phase identification, and thermal stability were examined by SEM, EDS, VSM and TGA, respectively. The fabricated total thicknesses of the proposed single slab ultra-high temperature radar absorber correspond to 1.585 mm, respectively, exhibiting their excellent EM absorption performance. The behavior of ultra-high temperature EM wave absorption properties was verified to the developed free-space measurement system linked with high temperature furnace for X-band from 25℃ to 1,000℃.