• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.267-274
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• 2005

This paper presents the fabrication of surface acoustic wave (SAW)-based pressure sensor for long-term stable mechanical compression force measurement. SAW pressure sensor has many attractive features for practical pressure measurement: no battery requirement, wireless pressure detection especially at hazardous environments, and easy other functionality integrations such as temperature, humidity, and RFID. A $41^{\circ}$ YX $LiNbO_3$ piezoelectric substrate was used because of its high SAW propagation velocity and large values of electromechanical coupling factors $K^2$. A silicon substrate with $\~200{\mu}m$ deep cavity was bonded to the diaphragm with epoxy, in which gold was covered all over the inner cavity in order to confine electromagnetic energy inside the sensor, and provide good isolation of the device from its environment. The reflection coefficient $S_{11}$ was measured using network analyzer. High S/N ratio, sharp reflected peaks, and clear separation between the peaks were observed. As a mechanical compression force was applied to the diaphragm from top with extremely sharp object, the diaphragm was bended, resulting in the phase shifts of the reflected peaks. The phase shifts were modulated depending on the amount of applied mechanical compression force. The measured $S_{11}$ results showed a good agreement with simulated results obtained from equivalent admittance circuit modeling.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.39-44
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• 2006

This paper proposes a method of moments(MoM)/Monte-Carlo simulation and Physical Optics(PO) model to determine Bistatic Coherent Reflectivity of sea surfaces at various wind speeds. For the MoM simulation, a Gaussian random rough sea surface was generated based on the data of Tae-An ocean at various wind speeds and sea surface heights. The numerical results of the MoM/Monte Carlo simulations were used to verify the validity region of the PO model. It was found that the numerical result for a flat surface agrees quite well with the Fresnel reflection coefficient. The validity of the PO model on the rough sea surface is shown by using ray tracing method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.24-38
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• 2006

In this paper, we investigate the design and fabrication of a conical spiral antenna suitable for satellite TT&C applications. The shape of the spiral is optimized using a commercial electromagnetic software for good gain and axial ratio performances over $2.0{\sim}2.3\;GHz$ frequencies. A coaxial infinite balun feeding the spiral is designed using experimental methods. A method for precision fabrication of the spiral is presented. Measurements of the fabricated antenna show satisfactory performances over $2.0{\sim}2.3\;GHz$ such as a reflection coefficient less than -18 dB, a maximum gain greater than 4 dB, a gain greater than 0 dB over angles ${\pm}75^{\circ}$ from the antenna boresight, an axial ratio less than 5 dB over angles ${\pm}90^{\circ}$ from the antenna boresight, a front-back ratio greater than 15 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.5
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• pp.416-423
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• 2016

In this paper, a conformal type $1{\times}4$ microstrip patch array antenna with tilted antenna beam is presented for UWB sensor applications. Each antenna element comprises E-shaped patch with L-probe feeding to increase the bandwidth. The tilted antenna beam of 20 degree can be achieved with 42 ps microstrip delay lines at the series feeding network with T-junctions. The measured reflection coefficient is >9 dB at 3.5~4.5 GHz. The measured antenna gain and HPBW are >10 dBi and <30 degree at 3.75~4.25 GHz.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.25-30
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• 2017

In this paper, dual band patch antenna was designed using a CSRR structure with negative values permeability which inserted into the ground plane. We propose an antenna that can be used in dual band f1(1.53GHz) and f2(1.63GHz) for satellite communications by using the CSRR placed on the backside of feeding line, which is a negative shape of SRR. The proposed antenna can be arrayed using microstrip line and can be made smaller than conventional patch antenna. The fabricated antenna has the input reflection coefficient of -12.5dB and -14.5dB at f1 and f2, and the gain of 2dB and -0.8dB, respectively. and it was confirmed that the performance was sufficient in the dual-band.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.3
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• pp.10-14
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• 2017

A reverberation chamber is widely used in mobile handset measurements due to its faster and simpler measurement process compared to traditional anechoic chambers. We propose an ultra-wideband inverse conical antenna design suitable as a reference antenna in a reverberation chamber. Traditionally, multiple discone antennas are needed to cover more than 10:1 operation bandwidth of a reverberation chamber. The proposed inverse conical antenna offers wideband impedance matching bandwidth by virtue of the linear impedance transition along its oblique side. The antenna is feasible to mount on the conductive walls which can be utilized as a ground to improve the matching bandwidth, antenna gain and radiation patterns. The antenna geometry is optimized using a 3D electromagnetic simulation tool and fabricated using a 3D printer. The measured results show that the antenna reflection coefficient lower than -10dB and radiation efficiency more than 70% at the frequency range of 0.65~7 GHz.

• Journal of Sensor Science and Technology
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• v.29 no.1
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• pp.27-32
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• 2020

This study proposes a pixel-patterning method for organic light-emitting diodes (OLEDs) based on thermal transfer. An infrared lamp was introduced as a heat source, and glass type donor element, which absorbs infrared and generates heat and then transfers the organic layer to the substrate, was designed to selectively sublimate the organic material. A 200 nm-thick layer of molybdenum (Mo) was used as the lightto-heat conversion (LTHC) layer, and a 300 nm-thick layer of patterned silicon dioxide (SiO₂), featuring a low heat-transfer coefficient, was formed on top of the LTHC layer to selectively block heat transfer. To prevent the thermal oxidation and diffusion of the LTHC material, a 100 nm-thick layer of silicon nitride (SiN_x) was coated on the material. The fabricated donor glass exhibited appropriate temperature-increment property until 249 ℃, which is enough to evaporate the organic materials. The alpha-step thickness profiler and X-ray reflection (XRR) analysis revealed that the thickness of the transferred film decreased with increase in film density. In the patterning test, we achieved a 100 ㎛-long line and dot pattern with a high transfer accuracy and a mean deviation of ± 4.49 ㎛. By using the thermal-transfer process, we also fabricated a red phosphorescent device to confirm that the emissive layer was transferred well without the separation of the host and the dopant owing to a difference in their evaporation temperatures. Consequently, its efficiency suffered a minor decline owing to the oxidation of the material caused by the poor vacuum pressure of the process chamber; however, it exhibited an identical color property.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.8
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• pp.93-97
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• 2004

Since powerline for powerline communications (PLC) is designed for supplying electric power using 60 Hz wave, they will have different electrical behaviors for high data rate PLC whose bandwidth is allocated between 1 MHz and 30 MHz. Thus, it is necessary to investigate the different properties in this frequency bandwidth for the high data rate PLC. In this paper, low voltage (220V) powerline impedance for indoor high data rate PLC in between 1 MHz and 30 MHz is measured. For measurement a low voltage coupling unit is made and a vector network analyzer is used. A T-equivalent circuit of the low voltage coupling unit is obtained and then powerline impedance is derived by measuring the reflection coefficient of the total powerline network. With the method proposed, impedance is measured in case of a general korean apartment and its property is analyzed. Measurement shows that the average impedance is about 100Ω.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.68-75
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• 2012

The load-insensitivity of the balanced power amplifier(PA) for W-CDMA handset applications is analyzed. The load impedances of the two parallel amplifiers in the balanced PA depending on the output load mismatch are mathematically calculated and with the result, the phase of reflection coefficient at which the linear output power is severely degraded is investigated. From the analysis, we proposed that the linearity of the balanced PA at the phase can be improved by properly increasing the transistor size and thus, multiple balanced PA's with different transistor size are designed and simulated. The simulation result showed that the balanced PA with larger transistor size has improved linear output power under VSWR=4:1.

• Journal of the Korean Institute of Navigation
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• v.25 no.1
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• pp.53-60
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• 2001

This paper presents the fabrication of the LNA which is operating at 2.13 ~ 2.16 GHz for IMT-2000 front-end receiver using series feedback and resistive decoupling circuit. Series feedback added to the source lead of a GaAs FET keeps the low noise characteristics and drops the input reflection coefficient of a low noise amplifier simultaneously. Also, it increases the stability of the LNA. Resistive decoupling circuit is suitable for input stage matching because a signal at low frequency is dissipated by a resistor in the matching network. The amplifier consists of GaAs FET ATF-10136 for low noise stage and VNA-25 which is internally matched MMIC for high gain stage. The amplifier is fabricated with both the RF circuits and self bias circuit on the Teflon substrate with 3.5 permittivity. The measured results of the LNA which is fabricated using the above design technique are presented more than 30 dB in gain, PldB 17 dB and less than 0.7 dB in noise figure, 1.5 in inputㆍoutput SWR(Standing Wave Ratio).