• Journal of electromagnetic engineering and science
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• v.13 no.1
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• pp.8-15
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• 2013

This paper presents a novel design for a simple rectangular ring with an open-ended monopole antenna that is well suited to DCS/PCS/UMTS/WLAN applications for dual-band operations. A microstrip-fed rectangular monopole antenna is first designed and then modified to introduce the rectangular ring with an open-ended antenna and a rectangular slit in the ground plane. Prototypes of the proposed antenna were fabricated and tested. The antenna, resonating at 1,405 MHz and 4,840 MHz, has a -10 dB impedance bandwidth of about 1,695 and 1,530 MHz (1,220~2,815 and 4,495~6,025 MHz), or about 79.06 % and 29.09 %. The observed 2D radiation patterns and 3D gain performance of the antenna in the operation bands are discussed.

• Journal of electromagnetic engineering and science
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• v.18 no.4
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• pp.215-220
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• 2018

This study presents a dual-band polarization-reconfigurable antenna that comprises a large square patch with a pair of corner-cut edges and two small square patches with a shorting via. Two PIN diodes are located between the large square patch and two small square patches. Depending on the bias state applied to the two PIN diodes, each small patch may be disconnected or connected to the large square patch. As a result, the proposed antenna can provide polarization reconfigurability between two orthogonal linear polarizations. Further, the proposed antenna operates at 2.51 GHz and 2.71 GHz. From the measured results, the proposed antenna shows a 10 dB bandwidth of 2.39% (2.49-2.55 GHz) and 2.58% (2.68-2.75 GHz). In this work, the frequency ratio can be easily controlled by changing the size of the small patch.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1046-1049
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• 2002

In this paper, a sub-harmonic dual-gate FET mixer for IMT-2000 base-station was designed by using single-gate FET cascode structure and driven by the second order harmonic component of LO signal. The dual-gate FET mixer has the characteristic of high conversion gain and good isolation between ports. Sub-harmonic mixing is frequently used to extend RF bandwidth for fixed LO frequency or to make LO frequency lower. Furthermore, the LO-to-RF isolation characteristic of a sub-harmonic mixer is better than that of a fundamental mixer because the frequency separation between the RE and LO frequency is large. As RF power is -30dBm and LO power is 0dBm, the designed mixer shows the -47.17dBm LO-to-RF leakage power level, 10dB conversion gain, -0.5dBm OIP3, -10.5dBm IIP3 and -1dBm 1dB gain compression point.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.417-420
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• 2003

Most Embedded Web Camera Server products currently deployed on the market adopt JPEG for compression of video data continuously acquired from the cameras. However, JPEG does not efficiently compress the continuous video stream, and is not appropriate for the Internet where the transmission bandwidth is not guaranteed. In our previous work, we presented the result of designing and implementing an embedded web camera streaming server using MPEG4 codec. But the server in our previous work did not show good performance since one CPU had to both compress and process the network transmission. In this paper, we present our efforts to improve our previous result by using dual CPUs, where DSP is employed for data compression and StrongARM is used for network processing. Better performance has been observed, but it is found that still more time is needed to optimize the performance.

• ETRI Journal
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• v.39 no.1
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• pp.69-75
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• 2017

This study presents a dual-band 3D frequency selective surface that provides a large degree of freedom in frequency and bandwidth adjustability. The proposed structure is evaluated in terms of its structural parameters, and prototypes are fabricated. The radius of the copper rings and the height of the cylinders are considered, and are shown through full-wave electromagnetic simulations to have a significant effect on the frequency characteristics of the frequency selective surface. The measurement results of the fabricated samples are compared with the simulation results, and a satisfactory agreement is obtained.

• ETRI Journal
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• v.39 no.3
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• pp.383-389
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• 2017

A small dual-polarized base station antenna with a simple isolation patch is presented. A high isolation is achieved when using a shorted metallic isolation patch. The experimental results indicate that the measured impedance bandwidth of the proposed antenna is 1.72 GHz to 1.89 GHz for small cell systems and that the isolation is more than 30 dB. The proposed antenna exhibits good radiation patterns with a peak gain of 8 dBi.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.3
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• pp.127-133
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• 2006

This Paper describes a dual bands PD measurement method which has two different bandwidths. The one bandwidth is 0.5 - 2 GHz and the other is 1 - 2GHz. This method is used for GIS diagnosis. In the experiment, it shows that the ratios between two PD quantities in dual bands depend on the defect types and gas pressures. The variations of ratios in different pressures are more sensitive than ones in defect types. And These ratios increase with increasing SF6 gas pressures. As these ratios give us additive information of PD we can analyze the defect type as well as risk assessment for the GIS reliably. Therefore the above result shows that these ratios are one of parameters for diagnosing GIS.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.493-495
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• 2007

Future sub-meter resolution LEO missions require simultaneous dual-polarization downlink and/or multiple channel downlinks in single polarization. Especially, dual-polarization is needed to cope with bandwidth limitation due to high speed data transmission. Current KARI 13m X-Band antenna system needs to be upgraded to cope with such downlink schemes. This paper describes brief discussions on engineering work regarding how to meet the new requirements with minimum impact on current system as well as C&M (Control and Monitoring) software.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1275-1279
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• 2012

In this paper, we design of dual-band microstrip antenna for wireless communication. We used IEEE 802.11a and Hyper LAN (5.725~5.825 GHz). The proposed antenna substrate is FR-4, size is $22mm{\times}23mm$, thickness is 1.6mm and used to CST Microwave Studio 2010 program. As a result the simulation has good result and good return loss below -10 dB at 5 GHz and 5.8 bandwidth.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.368-373
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• 2006

In this paper, a CPW fed rectangular slot antenna loaded with two slots for dual band operation is presented. This antenna operates at about 2.1GHz and 3.3GHz with the broad bandwidth at these frequencies. a CPW inset structure is used to match the antenna at the two seperated frequencies. Some prototypes of the proposed dual frequency antenna have been implemented. Experimental results are presented and discussed.