• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.168-175
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• 2013

This paper presents compact dual-band WLAN filter and filter module. They were developed by embedding all of the passive lumped elements into a LTCC substrate. In order to reduce the size/volume of the filter and avoid EM parasitic couplings between the passive elements, the proposed filter was designed using a 3rd order Chebyshev circuit topology and J-inverter transformation technology. The 3rd order Chebyshev bandpass filter was firstly designed for the band-selection of the 802.11b and was then transformed using finite transmission zeros technologies. Finally, the dual-band filter was realized by adding two notch resonators to the 802.11b filter circuit for the band-selection of the 802.11a/g. The maximum insertion losses in the lower and higher passbands were better than 2.0 and 1.3 dB with minimum return losses of 15 and 14 dB, respectively. Furthermore, the filter was integrated with a diplexer to clearly split the signals between 2 and 5 GHz. The maximum insertion and minimum return losses of the fabricated module were 2.2 and 14 dB at 2.4 - 2.5 GHz, and 1.6 and 19 dB at 5.15 - 5.85 GHz, respectively. The overall volume of the fabricated filter was $2.7{\times}2.3{\times}0.59mm^3$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.982-988
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• 2002

This paper summarizes the design concepts and implementation of a Ku-band channel amplifier's engineering model for the communication and broadcasting satellite applications. The selected architecture uses the analog gain control for the FGM(Fixed Gain Mode) and the output level limiting using automatic loop control for the ALC (automatic level control) mode. The Ku-band channel amplifier incorporates several state-of-the-art components including voltage-controlled PIN diode attenuators, and various temperature-compensation circuits. The measured characteristics of the Ku-band channel amplifier are in good agreement with the expected performance. The results show a fixed gain control of 28 dB, and an automatic level control of 16 dB over operating temperature range. The designed engineering model could be used as a channel amplifier for Ku-band communication and broadcasting satellite payload system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.783-789
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• 2002

In this paper, V-band MMIC coupled oscillator arrays are presented. In the proposed array, two push-pull patch antennas are synchronized by using strong electromagnetic coupling between two antennas. As a result, total size of the array is reduced and the array can be integrated in a single chip. To verify proposed array concept, two 1$\times$2 arrays are designed and fabricated using standard 0.15 um gate length pHEMT MMIC process. The circuits are mounted in an oversized waveguide and measured. The first array shows 0.5 dBm at 56.372 GHz and the second one has an output of 5.85 dBm at 60.147 GHz.

• Journal of electromagnetic engineering and science
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• v.15 no.1
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• pp.6-13
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• 2015

In this paper, a novel monopole antenna for WLAN/WiMAX application is presented. The proposed antenna consists of two arc-shaped strips, a vertical strip, and a slot in the ground plane. In this study, a prototype of the proposed triple-band antenna was designed, fabricated, and tested. The quantitative and experimental results demonstrate that the proposed antenna satisfy the -10 dB impedance bandwidth requirement of 440 MHz for 2.4/2.5 GHz bands (from 2.26 to 2.70 GHz), 970 MHz for 3.5 GHz bands (from 3.27 to 4.24 GHz), and 870 MHz for the GHz bands (from 5.08 to 5.95 GHz), while simultaneously covering the WLAN and WiMAX bands. In addition, the presented triple-band antenna has an omnidirectional radiation pattern at all three frequency bands with an antenna gain of 4.45 dBi for the lowest band, 2.04 dBi for the middle band, and 3.98 dBi for the highest band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.5
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• pp.355-365
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• 2017

In this paper, we propose the design of a dual-band GPS antenna using in-direct feeding pads. The antenna consists of an upper patch for the GPS L1 band, a lower patch for the GPS L2 band, and two pads on the middle layer for feeding the two radiating patches. A hybrid chip coupler with a phase difference of $90^{\circ}$ is employed at the two feeding ports for achieving a broad circular polarization (CP) bandwidth. The proposed antenna shows bore-sight gains of 3.0 dBic(L1) and 5.1 dBic(L2), and axial ratios of 3.3 dB(L1) and 0.3 dB(L2) by measurement. The active element patterns of the fabricated array with 7 elements show bore-sight gains of -0.4 dBic (L1) and -2.4 dBic(L2), respectively. It proves that the proposed antenna structure is suitable for use in GPS array applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.81-89
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• 2009

We propose a D-ATR UWB (Differential-Average Transmitted Reference Ultra Wide Band) system based on impulse radio. The TR-UWB systems including traditional TR (Transmitted Reference) and ATR (Average TR), exhibit a problem of reduced data rate, since reference signals are additionally transmitted. To tackle this issue, the transmitter of the proposed D-ATR system employs a differential coding like the conventional D-TR system. In addition, the receiver of the proposed system has the structure that can improve signal-to-noise ratio of the reference template used in the correlation process, by recursively averaging the received reference signals like the conventional ATR system. The simulation results in the IEEE 802.15.4a UWB multipath channel models reveal that the proposed D-ATR system achieves much better bit error rate performance as compared to the conventional D- TR system.

• Journal of the Korean earth science society
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• v.23 no.1
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• pp.1-14
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• 2002

The land-cover of two regions of South and North Korea included in one Landsat TM scene was investigated by comparing different seasons and different band data over the multiple land-cover types. The relationships between the intensities of two bands in the 2-D plot are mainly linear in band2 versus band1 and band3 versus band1, polygonal sporadic in band5 versus band1 and band7 versus band1, and almost tri-polarized in band4 versus band3. The 2-D plot of band4/band3 shows the best capability to discriminate different main land-cover such as water, vegetation and dry soil. Some discriminations are not clear between city and dry field, or mountain and plain field in the scene of September. The digital number data of band4 from vegetated zones show stronger reflectance in September rather than April, while other band values tend to be lager in April than in September over each land-cover. NDVI presents high value in both regions in September. However the image of Wonsan area in April suggests weak vigor of vegetation in comparison with Cholwon area. Band ratios are very effective in eliminating the influence of the complex topography. The proper pairing of the band ratio improved the discrimination capability of the land-cover; band5/band2 for dry soil, band4/band3 for vegetation and band1/band7 for the water. The RGB combination of the three band ratio pairs showed the best results in the discrimination of the land-cover of Wonsan, Cholwon and even the Demilitarized Zone.

• ETRI Journal
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• v.33 no.5
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• pp.818-821
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• 2011

A D-band subharmonically-pumped resistive mixer has been designed, processed, and experimentally tested. The circuit is based on a $180^{\circ}$ power divider structure consisting of a Lange coupler followed by a ${\lambda}$/4 transmission line (at local oscillator (LO) frequency). This monolithic microwave integrated circuit (MMIC) has been realized in coplanar waveguide technology by using an InAlAs/InGaAs-based metamorphic high electron mobility transistor process with 100-nm gate length. The MMIC achieves a measured conversion loss between 12.5 dB and 16 dB in the radio frequency bandwidth from 120 GHz to 150 GHz with 4-dBm LO drive and an intermediate frequency of 100 MHz. The input 1-dB compression point and IIP3 were simulated to be 2 dBm and 13 dBm, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.239-246
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• 2013

In this paper, a dual-band on-body antenna operating at MICS and ISM band for a wireless medical repeater system is proposed and the antenna performance including the human body effect is investigated. The designed dual-band antenna is comprised of a top patch for ISM band and bottom patch for MICS band. Simulation and measurement was carried out in order to analyze the effects of human body on antenna performance considering real use. The proposed antenna has required impedance bandwidth enough to cover both MICS and ISM bands. The measured peak gains were -12.47 dBi and 1.71 dBi at the each center frequency of MICS and ISM bands, respectively. Furthermore, the antenna has the maximum radiation directed toward the inside of the human body in the MICS band and directed toward the outside in the ISM band. In addition, the return loss property of the antenna is insensitive to human body effects so that the proposed antenna is well suited for the on-body wireless medical repeater system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.8
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• pp.68-73
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• 2010

In this paper, a compact Ultra-Wideband band-pass filter with notched band at 5.8GHz by using LC resonator is proposed. The structure of the proposed band-pass filter is very simple, and the DGS(Defected Ground Structure) is used to get the low-pass filter characteristics and the LC resonator is used to get the notched filter. The proposed band-pass filter can be much smaller than a cascaded filter type. The LC resonator is designed with a radial stub and small stub. As a result of measurement, the insertion loss is less than 0.5dB throughout the pass-band of 2.21GHz~10.92GHz, the return loss is more than 16dB and the maximum variation of group delay is 0.29ns and a notched band is 5.2GHz~6.2GHz.