• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1604-1611
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• 2003

For dual­band operation, it can be done by loading two pair of slits in the equilateral­triangular patch, one embeded close to the side edges of the patch and the other inserted at the bottom edge of the patch. The frequency ratio of the two operating frequencies can be tuned by varing the positions and lengths of the inserted slots at the bottom edge of the patch. While the calculated frequency ratio of the antenna by Ensemble 5.0 is $1.66 ({f_10}=1.928GHz, {f_20}=3.2GHz)$, the measured one is 2.04 $({f_10}=1.6806 GHz, {f_20}=3.435 GHz)$. The error in the frequency ratio is due on the fabrication dimension and feeding position error as well as on the permittivity dispersion effect.

• Journal of electromagnetic engineering and science
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• v.13 no.1
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• pp.34-37
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• 2013

This paper presents a novel ultra-wideband (UWB) antenna that rejects narrow and broad bands and is suitable for wireless communications. The base of the proposed antenna has a circular patch that can cover the UWB frequency range (3.1~10.6 GHz). The interference issues caused by co-existence within the UWB operation frequency are overcome by a design that uses a parallel-coupled asymmetric dual-line with a circular monopole antenna. The proposed antenna showed a stable radiation pattern, realized gain and reflection coefficient lower than -10 dB across the UWB operation bandwidth except for 5.15~5.85 GHz and 7.25~8.4 GHz. The fabrication, simulation, and measurement results obtained for the proposed antenna were in good agreement with the expected values.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.4
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• pp.493-500
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• 2015

A flyback converter operates with either pulse width modulation (PWM) or pulse frequency modulation (PFM) control scheme depending on the load current. At light load condition, PFM control is employed to reduce the switching frequency and thereby minimize the switching power loss. For heavier load, PWM control is used to regulate the output voltage of the flyback converter. The flyback controller has been implemented in a $0.35{\mu}m$ BCDMOS process and applied to a 40-W flyback converter. The light-load power efficiency of the flyback converter is improved up to 5.7-% comparing with the one operating with a fixed switching frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.140-144
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• 2004

The selectable dual band LNA usually uses common source transistor pair each input of which is selectively driven at a different frequency in a series resonant form. This paper analyzes the degradation in noise figures of the MOSFET common source pair with series resonance when it is driven concurrently at both inputs with different frequencies as a concurrent dual band LNA. Results of analysis will be compared with the measured noise figures of CMOS LNA with double inputs fabricated in 0.18 $\mu\textrm{m}$ CMOS process. Additionally, analyzing the contributions of FET channel noise and source noise from the LNA operating in the other band, this paper proposes optimum matching topology which minimizes the added noises for concurrent operation.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.7
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• pp.987-994
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• 2013

In this paper, a dual-band open-ended circular ring moNopole antenna for WLAN(Wireless Local Area Networks) applications. The proposed antenna is based on a planar moNopole design, and composed of open-ended one circular ring of radiating patches for dual-band operation. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and found the parameters that effect antenna characteristics. Using the obtained parameters, the proposed antenna is fabricated. The fabricated antenna is measured at the operating frequencies(2.4-2.484 GHz, 5.15-5.825 GHz), and the return loss coefficient, gain, and radiation patterns are determined.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.547-551
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• 2010

In this paper, Double rectangular patch with 4-bridges is investigated for solution of IEEE 802.11b/g(2.4GHz) and 802.11a(5.7GHz). Rectangular patch for 5.7GHz frequency band is printed on the PCB substrate and connected to another rectangular patch for 2.4GHz frequency band with 4-bridges to obtain dual band operation in a antenna element. The proposed antenna has a low profile and is fed by $50{\Omega}$ coaxial line. The dielectric constant of the designed antenna substrate is 3.27. Two rectangular patches have each resonance frequencies that are 2.4GHz and 5.7GHz. A dual-band characteristic is shown as connecting two rectangular patch using four bridges. Also, the proposed antenna is shown input return loss that is below -10dB at 2.4GHz and 5.7GHz of WLAN(Wireless LAN).

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.436-441
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• 2018

In this paper, a design method for a compact double dipole quasi-Yagi antenna with a V-shaped ground plane operating in dual bands including 2.45 GHz and 5 GHz wireless LAN frequency bands is studied. First, a quasi-Yagi antenna operating in the 2.45 GHz band is designed, and a V-shaped ground plane is used instead of a conventional strip ground plane to reduce the length of the antenna. A second dipole is connected to the dipole driver of the quasi-Yagi antenna for 2.45 GHz band and a director is appended for 5 GHz band operation. A prototype of the proposed dual-band antenna operating at 2.45 GHz WLAN band and 4.57-7.11 GHz band is fabricated on an FR4 substrate with a dimension of 40 mm by 55 mm. Fabricated antenna shows frequency bands of 2.33-2.75 GHz and 4.38-7.5 GHz for a voltage standing wave ratio less than 2. Measured gain remains more than 4 dBi in both bands.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.35-40
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• 2008

This paper proposes a dual-band balun which is based on Wilkinson power divider. By inserting $\lambda/2$ transmission line between port 2 and 3, this balun shows good matching at all ports and improved isolation. We use matamaterial(CRLH, D-CRLH) structure for a miniaturization of the circuit implementation and dual-band operation at TDMB frequency range(195MHz) and DVB-H frequency range(670MHz). The proposed balun is designed with return loss larger than -12.98dB at all port, and isolation larger than -12.4dB, the amplitude imbalance between output signals less than 0.08dB, also phase differences of outputs less than $2.8^{\circ}$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.11
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• pp.9-16
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• 2005

This paper proposes a programmable PLL (phase locked loop) based clock generator supporting a wide-range-frequency input and output for high performance and low power SoC with multiple clock frequencies domains. The propose system reduces the locking time and obtains a wide range operation frequency by using a dual-charge pumps scheme. For low power operation of a chip, the locking processing circuits of the proposed PLL doesn't be working in the standby mode but the locking data are retained by the DAC. Also, a tracking ADC is designed for the fast relocking operation after stand-by mode exit. The programmable output frequency selection's circuit are designed for supporting a optimized DFS operation according to job tasks. The proposed PLL-based clock system has a relock time range of $0.85{\mu}sec{\sim}1.3{\mu}sec$($24\~26$cycle) with 2.3V power supply, which is fabricated on $0.35{\mu}m$ CMOS Process. At power-down mode, PLL power saves more than $95\%$ of locking mode. Also, the PLL using programmable divider has a wide locking range ($81MHz\~556MHz$) for various clock domains on a multiple IPs system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.899-905
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• 2008

In this paper, we propose a dual-spiral line loaded monopole antenna having a vertical ground plane for quadband applications. The antenna occupies a volume of $38{\times}12{\times}7\;mm^3$ with a $40{\times}92\;mm^2$ ground plane. The measured impedance bandwidths of the antenna based on $VSWR{\le}2$ are approximately of 11.7 % and 24.8 % in the first and second frequency band, respectively. The operating frequency can simultaneously cover Cellular($0.824{\sim}0.894\;GHz$), PCS($1.750{\sim}1.870\;MHz$), UMTS($1.920{\sim}2.170\;MHz$), and IMT-2000($1.885{\sim}2.200\;GHz$) bands. The maximum gains of the antenna are -0.99 dBi, 4.07 dBi, 2.72 dBi, and 4.33 dBi at the center frequencies of the Cellular, PCS, UMTS, and IMT-2000 bands, respectively. Good radiation patterns are experimentally obtained.