• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.10
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• pp.761-768
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• 2017

In this paper, to implement the electromagnetic wave environment and solve electromagnetic compatibility(EMC) problem, miniaturization of ultra-wide band log periodic dipole antenna for measurement was investigated. In addition, in oder to improve the signal-to-noise ratio in high frequency band, balun was connected to the antenna to stabilize the operation of the differential mode antenna and the single mode coaxial cable. To minimize the total size and to increase bandwidth of the antenna, a fat dipole structure was used for the resonance frequency band below 4 GHz and a general dipole shape was used for that above 4 GHz. The bandwidth of the proposed antenna was represented from 0.6 GHz to 8.0 GHz with a ratio bandwidth of 12.3 : 1. Measured peak gain varies from 5.7 dBi to 9.1 dBi, and a half power beamwidth was presented from $29.4^{\circ}$ to $100.2^{\circ}$ in operating range.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.3
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• pp.21-26
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• 2024

Design and fabrication method of W-band 12-way radial power combiner is proposed in this paper. The proposed structure is used with TE₁₀ to TEM mode converter, which is realized using 2-step impedance transformer. The pin structure for mode converter is well bonded to the housing so that environment conditions such as vibration or shock are not affected. Proposed W-band power combiner has less than 0.7 dB insertion loss and more than 13 dB return loss from 88 GHz to 98 GHz. The measured output isolations between each other are greater than 7.5 dB from 82 to 100 GHz and phase differences are less than 10 degree from 88 to 96 GHz. Proposed power combiner is expected compact radar and various applications requiring for high power and stable environment conditions.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.506-510
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• 2016

A triple-band (TB) oscillator was implemented in the TSMC $0.18{\mu}m$ 1P6M CMOS process, and it uses a cross-coupled nMOS pair and two shunt $4^{th}$ order LC resonators to form a $6^{th}$ order resonator with three resonant frequencies. The oscillator uses the varactors for band switching and frequency tuning. The core current and power consumption of the high (middle, low)- band core oscillator are 3.59(3.42, 3.4) mA and 2.4(2.29, 2.28) mW, respectively at the dc drain-source bias of 0.67V. The oscillator can generate differential signals in the frequency range of 8.04-8.68 GHz, 5.82-6.15 GHz, and 3.68-4.08 GHz. The die area of the triple-band oscillator is $0.835{\times}1.103mm^2$.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.83-89
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• 2014

A ku-band complementary cross-coupled differential voltage controlled oscillator is designed, measured and fabricated using $0.18-{\mu}m$ CMOS technology. A 2.4GHz of very wide frequency tuning at oscillating frequency of 14.5GHz is achieved with presented circuit topology and MOS varactors. Measurement results show -1.66dBm output power with 18mA DC current drive from 3.3V power supply. When 5V is applied, the output power is increased to 0.84dBm with 47mA DC current. -74.5dBc/Hz phase noise at 100kHz offset is measured. The die area is $1.02mm{\times}0.66mm$.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.4
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• pp.181-185
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• 2017

In this paper, for Broadband Wireles LAN dual-band antenna was designed to satisfy the bandwidth of 2.32GHz and 5.79GHz. the substrate of proposed microstrip antenna is FR-4(er=4.3) and $34mm{\times}50mm{\times}1.5mm$ size and thickness t=0.035mm, and the simulation was used for CST Microwave Studio 2014. input return loss compared -10dB less than operates at and when gain 2.32GHz -19.321dB, 5.79GHz showed the results of -13.033dB. It increased impedance matching, minimized interference between adjacent frequencies, simplified small manufacturing methods, and demonstrated the characteristics of non-directional properties. Thus the proposed antenna satisfied the -10 dB impedancebandwidth requirement while simultaneously covering the Broadband Wireless LAN.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.223-230
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• 2014

In this paper, the single-fed microstrip parasitic array antenna for low-cost three-dimensional beam steering in 5.8GHz ISM(5.725GHz~5.825GHz) band is designed and implemented. The antenna is comprised of one feed active element and four passive elements with variable reactance loads. The beam steering range of implemented antenna is achieved three-dimensional beam steering of ${\pm}28^{\circ}$ at azimuth angle ${\Phi}=0^{\circ}$, ${\Phi}=45^{\circ}$, ${\Phi}=90^{\circ}$, and ${\Phi}=135^{\circ}$ by adjusting variable reactance loads. The maximum gain of the antenna in the beam steering range have within 7.23dBi~9.36dBi and the bandwidth of return loss lower than -10dB covers 5.8GHz ISM band regardless of the beam steering angles.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.9
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• pp.1633-1640
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• 2016

In this paper, we propose a open-ended rectangular microstirp patch antenna with fork-shaped feeding structure. This antenna extends the effective bandwidth by transforming single or multi resonant frequency and is designed planar monopole structure with microstrip line to satisfy the WLAN bands (2.4 - 2.484, 5.15 - 5.35, 5.25-5.825 GHz). The substrate is printed in 0.8 mm thickness on an FR-4 board. A commercial 3D simulation tool was used to analyze surface current and electromagnetic field distribution in order to analyze the operation mode and reconfiguration principle of antenna. According to the lengths of individual patches, simulated reflection loss was compared to obtain optimized values. When it was designed with the optimized values, it satisfied WLAN bands (2.380 - 2.710, 4.900 - 5.950 GHz), if the switch is off, and 2.4 WLAN band (2.380 - 2.710 GHz). From the fabricated and measured results, measured results of return loss, gain and radiation patterns characteristics displayed for operating bands.

• Journal of IKEEE
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• v.23 no.2
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• pp.425-430
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• 2019

This work describes the design and characterization of a X-band power amplifier (PA) monolithic microwave integrated circuit (MMIC) using a $0.25{\mu}m$ gate length gallium nitride (GaN) high electron mobility transistor (HEMT) technology. The developed X-band power amplifier MMIC has small signal gain of over 22.7 dB and saturated output power of 43.02 dBm (20.04 W) over the entire band of 9 to 10 GHz. Maximum saturated output power is a 43.84 dBm (24.21 W) at 9.5 GHz. Its power added efficiency (PAE) is 41.0~51.24% and the chip dimensions are $3.7mm{\times}2.3mm$, generating the output power density of $2.84W/mm^2$. The developed GaN power amplifier MMIC is expected to be applied in a variety of X-band radar applications.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.121-125
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• 2006

The frequency band $10.5GHz{\sim}10.7GHz$ provides some of the best angular resolutions that using many large and accurate radio telescopes. Developing high-performanced Bandpass Filter is needed for these equipments receive low power signals from the space. In this paper, Bandpass Filter for Radio Astronomy equipments is proposed. It is designed by Microstrip Line for good pass characteristic and suppressing unwanted signals. Center frequency is 10.6 GHz and band width is 5% of Center frequency. Manufactured Bandpass Filter is suitable for Radio Astronomy Equipments. Because the measured results agree well with the simulation results.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.33.1-33.1
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• 2016

We report detection of short-term flux variability in multi-epoch observations and intraday variability in polarized emission at millimeter-wavelength from S5 0716+714 using Korean VLBI Network (KVN) radio telescopes. Over the whole observation epochs, the source shows significant inter-month variations at K- and Q-band with modulation indices of 19% at K-band and 36% at Q-band. In each epoch, the source shows monotonic flux increase in Epoch 1 and 3, and monotonic flux decrease in Epoch 2 and 4. We found an inverted spectrum with mean spectral indices of -0.57 in Epoch 1 and -0.15 in Epoch. On the contrary, we found relatively steep indices of 0.24 and 0.17 in Epoch 2 and Epoch 4, respectively. In the study of intraday variability of polarization, we found significant variations in the degree of linear polarization at 86 GHz, and in polarization angle at 43 and 86 GHz during ~10 h. The spectrum of the source is quite flat with spectral indices of -0.07 to 0.07 at 22-43 GHz and -0.23 to 0.04 at 43-86 GHz. The measured degree of the linear polarization ranges from 2.3% to 3.3 % at 22 GHz, from 0.9% to 2.2 % at 43 GHz and from 0.4 % to 4.0 % at 86 GHz, yielding prominent variations at 86 GHz over 4-5 h. The linear polarization angle is in the range of 4 to $12^{\circ}$ at 22 GHz, -39 to $81^{\circ}$ at 43 GHz, and 66 to 119 at 86 GHz with a maximum rotation of $110^{\circ}$ at 43 GHz over ~4 h. We estimated the Faraday rotation measures (RM) ranging from -9200 to 6300 rad m-2 between 22 and 43 GHz, and from -71000 to 7300 rad m-2 between 43 and 86 GHz, respectively. The frequency dependency of RM was investigated, yielding a mean power-law index, a, of 2.0. This implies that the polarized emission from S5 0716+714 at 22-86 GHz moves through a Faraday screen in or near the jet of the source.