• Journal of electromagnetic engineering and science
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• 제9권3호
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• pp.159-163
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• 2009

This paper presents the design and implementation of Q-band MMIC phase shifters using InGaAs PIN diodes. The topology using a thin-film microstrip line(TFMS) has been proposed to achieve the desired phase-shift as well as good loss characteristics. Five single-bit MMIC phase shifters have been implemented by using a developed BCB(benzocyclobutene)-based multi-layer fabrication technology. The developed phase shifters have less than 3.4 dB of insertion loss and better than 11 dB of input and output return loss in the frequency range of 43 to 47 GHz. To the authors' knowledge, this is the first demonstration of high-performance InGaAs PIN diode-based MMIC phase shifters operating at Q-band frequencies.

• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.94-100
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• 2012

Radio interference has been occurring in mobile communication services on the southern seashore in Korea. Monitoring the radio interference signal revealed that the main reason for the radio interference was a radio ducting signal coming from the seaside of Japan. In this paper, we have analyzed the effect of interference on WiMAX service using a 2.5 GHz frequency band between Korea and Japan. We focus on the interference scenario from base station to base station and we use the Minimum Coupling Loss (MCL) method for interference analysis and the Advanced Propagation Model (APM) for calculating the propagation loss in ducts. The propagation model is also compared with experimental measurement data. We confirm that the interfering signal strength depends on the antenna height and this result can be applied to deployment planning for each system with an interference impact acceptable to both parties.

• Journal of electromagnetic engineering and science
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• 제7권1호
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• pp.47-52
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• 2007

We investigated the effects of substrate, metal-line, and surface material on the performance of radio frequency identification(RFID) tag antenna using a tag antenna with a meander line radiator and T-matching network. The results showed that readability of the tag antenna with a thin high-loss substrate could be increased so that it was similar to that of a low-loss substrate if the substrate was very thin. The readability of the tag antenna decreased significantly when the metal line was thinner than the skin depth. The readability of the tag also decreased drastically when the tag was attached to high-permittivity high-loss target objects.

• 한국전기전자재료학회논문지
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• 제23권10호
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• pp.809-813
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• 2010

Frequency domain measurement of propagation loss for ultra high frequency (UHF) partial discharge in the winding of power transformer using a spectrum analyzer and pulse generator is presented. We compared the performance of the method using a network analyzer with and without a winding. Using a network analyzer simplifies the measurement and offers better dynamic range and frequency range. It also provides precise propagation loss within the winding in frequency domain at UHF range. We applied this method to measure UHF propagation loss of transformer mock-up, modeled 154 kV 20 MVA power in KEPCO substation.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.233-237
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• 2000

Propagation losses including bath transmission losses and bending losses of the flexible dielectric tube waveguide using commercial polymer substances for a short distance millimeter wave transmission are analytically predicted. The transmission loss and the bending loss are strongly dependent on the power flow distributions in each region. The obtained propagation tosses are compared with those of the commercial metal rigid and flexible waveguides.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.165-170
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• 2010

Recently, Interior Permanent Magnet Machine(IPM) is widely used for traction motor in the high speed train. Higher efficiency and power density are the superb performance of IPM. Due to the high power density, however, it has lots of heat source which are originated from copper losses and core losses. These heat source can cause the permanent demagnetization in magnet and the loss of torque and power. To prevent the undesirable loss in the traction motor, the accurate loss calculation and the thermal analysis should be preceded. Especially, the end-winding area and permanent magnet area should be examined correctly. In this paper, the electromagnetic fields were examined by finite element method to analyze the electromagnetic properties of IPM and thermal analysis are carried out with pre-calculated losses. To validate the analysis result, the experiment set with forced air cooling system is manufactured.

• Journal of electromagnetic engineering and science
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• 제7권4호
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• pp.190-194
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• 2007

In this paper, a cross-coupled microstrip combline bandpass filter using stepped-impedance resonators(SIRs) is proposed. In order to improve the selectivity as well as the insertion loss, the SIR configuration is used. The cross coupling is also introduced to enhance the selectivity. The improvement of the insertion loss is demonstrated not only by deriving the quality factor of the SIR but through the measured performances. Both the proposed and the conventional combline bandpass filter with 5 % of fractional bandwidth at 2 GHz were fabricated and tested. Compared to the conventional combline bandpass filter, the proposed one exhibits the improved selectivity as well as the lower insertion loss characteristics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.916-917
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• 2015

This paper deals with electromagneitc characteristics analysis of high-speed brushless DC motor. First, under same rated and restricted conditions, four models which have different slot combinations each other are designed using 2-d finite element (FE) analyses. Designed models are analyzed and compared in terms of core loss, copper loss, eddy-current loss, etc. On the basis of analysis results, it is found that the motor with a 2-pole PM rotor and a 6-slot stator has most outstanding performances in electromagnetic aspects.

• Journal of electromagnetic engineering and science
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• 제14권4호
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• pp.382-386
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• 2014

The knowledge of substrate material properties is important in antenna design. We present a technique to accurately characterize the dielectric constant and loss tangent of an antenna substrate based on the measurements of antenna's reflection coefficient and bandwidth. In this technique, an error function is formulated by combinations of the reflection coefficient and bandwidth of measured and simulated data, and then an optimization technique is used to efficiently search for the substrate properties that minimize the error function. The results show that the method is effective in retrieving the dielectric constant and loss tangent of the antenna substrate without the need of additional test fixtures as in conventional substrate characterization methods.

• 설비공학논문집
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• 제29권7호
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• pp.366-372
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• 2017

The objective of this study was to characterize Waveguide-Blow-Cutoff (WBC) array for Electromagnetic Pulse (EMP) shield in air duct or water pipe, the typical pathway of pulse in indoor space with critical electronic device. A numerical investigation with three different WBC designs (circular, rectangular, and hexagonal or honeycomb) was conducted to satisfy recommended shielding effectiveness (SE) levels from 80 dB to 140 dB. Pressure drop between upstream and downstream of EMP shields based on WBC arrays was also investigated to understand air flow feature in air duct of HVAC system. Results showed that honeycomb geometry outperformed other shapes in terms of reducing the depth of EMP shield, thus providing better air flow in duct path with lower local loss coefficient in HVAC system under SE requirements.