• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.139-141
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• 2009

This paper presents a design and analysis of torque characteristics of a two-phase SRM(Switched Reluctance Motor) for high speed blower system. To reduce the electrical frequency and core losses at high speed region, In order to reduce torque ripple and torque dead-band, variable rotor air-gap structure is adopted and the air-gap is optimized according to torque production. The optimized torque output is verified by the FEM results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.7
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• pp.1255-1260
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• 2009

Microstrip interdigital filter is designed with the width and length of a resonator, the gap distance between resonators and the location of a tap. When designing filters, it is a benefit to design with few design parameters comparing to many design parameters. In this paper we design and implement two microstrip interdigital filters operating in the UWB(Ultra Wide-Band) frequency band, one using a fixed width of a resonator and the other using a different width of resonators. The test results of the implemented filters show that the low-band high filter with a fixed width has the insertion loss of 1.49dB, -10dB band width of 720MHz, -35.7dBattenuation at 4.8GHzand below -13dB of S11. The filter with a different width of resonators has the insertion loss of 1.6dB, -10dBbandwidth of 1.63GHz and below-8dBof S11.

• Journal of electromagnetic engineering and science
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• v.7 no.3
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• pp.116-121
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• 2007

Novel design of a wideband monopole antenna for DVB-H service is presented. The proposed antenna is designed based on a monopole antenna. It consists of folded monopole and parallel parasitic element. The folded segment of the folded monopole makes the antenna shorter. The length of the parasitic element obtains additional resonance frequencies. The gap distance between the folded monopole and the parasitic element is a key parameter to control impedance matching for wideband operation. The antenna has wide band performance, good impedance and radiation characteristics from 470 MHz to 870 MHz. The measured return loss for operating frequencies over DVB-H band is better than 10 dB. Good radiation patterns are also obtained. The measured results are compared with calculated results using Ansoft HFSS(High Frequency Structure Simulator).

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.63-64
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• 2006

In this paper, the open loop antenna using a strip-conductor for an RFID reader at dual-band frequency(910MHz, 2.45GHz) is proposed. The impedance is matched by varying the antenna parameters such as the length of strip-conductor and the gap of between two strip-conductors. Return loss and gain of designed antenna are -11.919dB, 2.5dBi at 910MHz, and -15.766dB, 5.65dBi at 2.45GHz, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.184-184
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• 2008

In this paper, a power divider with a multi-band and broadband are designed and fabricated using an InGaP/GaAs process. The design of this divider is based on multi-band because it is important in the next generation IMT-Advances system. In this design, power divider is fabricated with the frequency of 824 MHz to 894 MHz, 1.8 GHz to 2.2 GHz and 2.3 GHz to 2.4 GH for cellular, personal communication system (PCS) and Wireless Broadband Internet (WiBro). The topology of the designed power divider is based on the multi-section and fabricated using integrated passive device (IPD) library of nanoENS Inc. It is measured using network analyzer.

• Current Photovoltaic Research
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• v.4 no.1
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• pp.25-29
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• 2016

$Eu^{3+}$-activated $MgMoO_4$ phosphor thin films were grown at $400^{\circ}C$ on quartz substrates by radio-frequency magnetron sputter deposition from a 15 mol% Eu-doped $MgMoO_4$ target. After the deposition, the phosphor thin films were annealed at several temperatures for 30 min in air. The influence of thermal annealing temperature on the structural and optical properties of $MgMoO_4:Eu^{3+}$ phosphor thin films was investigated by using X-ray diffraction (XRD), photoluminescence (PL), and ultraviolet-visible spectrophotometry. The transmittance, optical band gap, and intensities of the luminescence and excitation spectra of the thin films were found to depend on the thermal annealing temperature. The XRD patterns indicated that all the thin films had a monoclinic structure with a main (220) diffraction peak. The highest average transmittance of 91.3% in the wavelength range of 320~1100 nm was obtained for the phosphor thin film annealed at $800^{\circ}C$. At this annealing temperature the optical band gap energy was estimated as 4.83 eV. The emission and excitation spectra exhibited that the $MgMoO_4:Eu^{3+}$ phosphor thin films could be effectively excited by near ultraviolet (281 nm) light, and emitted the dominant 614 nm red light. The results show that increasing RTA temperature can enhance $Eu^{3+}$ emission and excitation intensity.

• Journal of the Korean Vacuum Society
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• v.19 no.5
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• pp.353-359
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• 2010

We report the surface photovoltage (SPV) properties of $In_{0.49}Ga_{0.51}P$/GaAs heterostructure grown by metal-organic chemical vapour deposition (MOCVD). The SPV measurements were studied as a function of modulation beam intensity, modulation frequency and temperature. From a line shape analysis of room temperature derivative surface photovoltage (DSPV) spectrum, the band gap energies for GaAs and $In_{0.49}Ga_{0.51}P$ transitions were 1.400 and 1.893 eV respectively. The surface photovoltage (SPV) increases with increasing the light intensity and temperature, whereas the SPV decreases with increasing the modulation frequency. From the temperature variation of the energy gaps, we have analysis by both Varshni and Bose-Einstein type expressions.

• Journal of IKEEE
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• v.16 no.1
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• pp.15-19
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• 2012

The frequency selective surfaces(FSSs) with chessboard patterns are proposed and designed for the first time in this paper. We proposed the design parameters like slot and patch size, gap between slots or patches, and dielectric thickness of FSS chessboard unit cell proposed in this paper. Also, we found that the variation of design parameters can be used to control the frequency transmission characteristics like the resonant frequency or bandwidth of FSS. To validate the proposed FSS, we fabricated the proposed FSS with the use of 1.0mm FR4 for the bandpass operation at X-band and measured the transmission characteristics. From the results, the proposed FSS with chessboard type can be widely applied to application of the frequency controllable radome design because we can use the design parameters selectively.

• Journal of information and communication convergence engineering
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• v.16 no.1
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• pp.12-16
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• 2018

In this work, a voltage controlled oscillator (VCO) monolithic microwave integrated circuit (MMIC) was demonstrated for 10-GHz band motion detecting sensors. The VCO MMIC was fabricated using a $2-{\mu}m$ InGap/GaAs HBT process, and the tuning of the oscillation frequency is achieved by changing the internal capacitance in the HBT, instead of using extra varactor diodes. The implemented VCO MMIC has a micro size of $500{\mu}m{\times}500{\mu}m$, and demonstrates the value of inserting the VCO into a single chip transceiver. The experimental results showed that the frequency tuning characteristic was above 30 MHz, with the excellent output flatness characteristic of ${\pm}0.2dBm$ over the tuning bandwidth. And, the VCO MMIC exhibited a phase noise characteristic of -92.64 dBc/Hz and -118.28 dBc/Hz at the 100 kHz and 1 MHz offset frequencies from the carrier, respectively. The measured values were consistent with the design values, and exhibited good performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.5745-5758
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• 2017

In this paper, we develop a simple but very effective 4 by 4 Multiple-Input Multiple-Output (MIMO) antenna system for mobile phones consisting of different types of antennas to achieve low correlation property at the frequency ranges of 1710 to 2170 MHz, which covers wide LTE service bands, from band 1 to band 4. The proposed antenna system consists of two pair of antennas. Each pair consists of a planar inverted-F antenna (PIFA) and a coupling antenna which has the property of the loop. The use of two different antenna types of IFA and a coupling achieves high isolation. Proposed antenna system occupies relatively small area and positions at the four corners of a printed circuit board. The gap between the two antennas is 4 mm, in order to realize the good isolation performance. To evaluate the performance of our proposed antenna system, we perform various experiments. The proposed antenna shows a wide operating bandwidth greater than 460 MHz with isolation between the feeding ports higher than 17.5-dB. It also shows that the proposed antenna has low Envelop Correlation Coefficient (ECC) values smaller than 0.08 over the all desired frequency tuning ranges.