• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.569-571
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• 2007

In this paper, hem antenna composed of rectangular hern, circular polarizer and straight-type mode convertor is designed and fabricated. The circular polarizer is designed as a dielectric type having broadband characteristic, and it is inserted into the rectangular hem with $45^{\circ}$ inclination. The straight-type mode convertor has a terrace-type structure in order to convert the TEM mode signal of coaxial cable to the TE mode of rectangular waveguide, and this structure minimizes conversion loss. Fabricated hem antenna operates at $30.085\sim30.885GHz$ and has VSWR < 1.5, Axial ratio < 1.0dB and antenna gain of $6.7\sim7.0dBi$ in the band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.864-870
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• 2017

This paper describes a Dual Buck Converter with mode control using variable Frequency to Voltage for portable devices requiring wide load current. The inherent problems of PLL compensation and efficiency degradation in light load current that the conventional hysteretic buck converter has faced have been resolved by using the proposed Dual buck converter which include improved PFM Mode not to require compensation. The proposed mode controller can also improve the difficulty of detecting the load change of the mode controller, which is the main circuit of the conventional dual mode buck converter, and the slow mode switching speed. the proposed mode controller has mode switching time of at least 1.5us. The proposed DC-DC buck converter was implemented by using $0.18{\mu}m$ CMOS process and die size was $1.38mm{\times}1.37mm$. The post simulation results with inductor and capacitor including parasitic elements showed that the proposed circuit received the input of 2.7~3.3V and generated output of 1.2V with the output ripple voltage had the PFM mode of 65mV and 16mV at the fixed switching frequency of 2MHz in hysteretic mode under load currents of 1~500mA. The maximum efficiency of the proposed dual-mode buck converter is 95% at 80mA and is more than 85% efficient under load currents of 1~500mA.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.4
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• pp.34-42
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• 2012

In this paper, a wide-input range CMOS multi-mode rectifier for wireless power transfer system is presented. The output voltage of multi-mode rectifier is sensed by comparator and switches are controlled based on it. The mode of multi-mode rectifier is automatically selected by the switches among full-wave rectifier, 1-stage voltage multiplier and 2-stage voltage multiplier. In full-wave rectifier mode, the rectified output DC voltage ranges from 9 V to 19 V for a input AC voltage from 10 V to 20 V. However, the input-range of the multi-mode rectifier is more improved than that of the conventional full-wave rectifier by 5V, so the rectified output DC voltage ranges from 7.5 V to 19 V for a input AC voltage from 5 V to 20 V. The power conversion efficiency of the multi-mode rectifier is 94 % in full-wave rectifier mode. The proposed multi-mode rectifier is fabricated in a $0.35{\mu}m$ CMOS process with an active area of $2500{\mu}m{\times}1750{\mu}m$.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.293-294
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• 2010

ITU-T와 ISO/IEC의 공동 작업으로 제정 된 H.264/AVC는 기존 비디오 표준들에 비해 동일한 화질에서 약 30%~70%의 비트 량을 절감할 수 있으며, 동일한 비트 량으로 PSNR이 2~3dB 가량 우수한 영상을 제공할 수 있다. H.264/AVC는 인트라 부호화 효율을 높이기 위해 공간 영역에서 주변 화소를 이용하여 $4{\times}4$ luma 예측의 9가지 모드와 $16{\times}16$ luma 예측의 4가지 모드에 대한 비트율-왜곡 최적화 기법을 사용하여 최적의 인트라 예측 모드를 선택한다. 본 논문에서는 프레임 내에서 공간 중복 성을 더 많이 줄이기 위해 9가지 모드의 $4{\times}4$ luma 예측에 7가지 모드를 추가하여 총16가지의 $4{\times}4$ luma 예측 모델을 제안한다. 그리고 실험을 통하여 제안하는 인트라 예측 모델이 기존 기술에 비해 높은 압축효율을 보인다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.1
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• pp.1-7
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• 2003

Leaky modes on a circular dielectric rod are investigated from the precisely determined normalized complex propagation constants using Davidenko's complex root finding technique. Below the cutoff frequency of the guided mode, distinct frequency regions that have unique properties are observed, such as nonphysical region, antenna mode region, reactive mode region, and spectral gap region.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.11a
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• pp.157-158
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• 2013

현재 MPEG에서 무료(Royalty-Free) 비디오 코덱으로 표준화 중인 IVC(Internet Video Coding)에서는 인트라 부호화를 위하여 DC 모드의 한 가지 예측 모드만 사용하고 있다. 이러한 기존의 인트라 부호화 기법은 부호화 모드를 시그널링할 필요가 없고 부호화 시간이 빠른 장점이 있지만 인트라 예측의 정확도가 많이 떨어짐에 따라 부호화 효율이 저하된다. 본 논문에서는 IVC의 인트라 부호화 성능 향상을 위하여 4 가지 예측 모드를 지원한다. 즉, 공간적 상관성을 고려하여 평활화된 참조화소 값을 사용하는 평활화된 다중모드 인트라 부호화 기법을 제안한다. 실험결과 제안된 기법은 All-Intra 부호화 구조에서 기존의 ITM 6.0 대비 7.4% 정도의 비트율 감소를 얻음을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.1
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• pp.14-19
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• 2010

In this paper, a novel architecture for device miniaturization of multimode interference-based couplers (MMICs) is proposed by replacing conventionally designed MMICs by cascaded two-section stepped-width or stepped-index MMICs. For the 82% cross coupling efficiency in a stepped-width MMIC, the coupling length of device results in just 6.7% length reduction. However, for a stepped-width and stepped-index MMIC, the coupling efficiency increases to 93% and the length reduction of 9% occurs. Furthermore, with additional incorporation of tapered devices, it shows that a compact MMIC can be designed in which the coupling efficiency is 90% and the length is reduced to 25%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.447-452
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• 2011

In this paper, we present a compact triple-mode resonator. The resonator itself can provide three transmission poles and one transmission zero. The resonance condition of each mode is analyzed theoretically, and the transmission zero is generated by open stub. Using this proposed resonator, a compact three pole bandpass filter for 2.4 GHz WLAN application with one transmission zero is designed and fabricated. The fabricated triple-mode filter shows 3 dB bandwidth of 15.8 % with the center frequency 2.4 GHz and less then 1.17 dB in 2.4~2.5 GHz passband. The size of fabricated triple-mode filter including the feed lines is 15.9 mm${\times}$9.7 mm and very compact compared with previous reported triple-mode filter.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.578-581
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• 2011

H.264/AVC에서는 율-왜곡 최적화 기법을 사용하여 부호화 성능을 이전 보다 대폭 향상시켰다. 율-왜곡 최적화 기법은 선택할 수 있는 모든 코딩 모드들의 비용을 계산한 후, 최소의 비용을 가진 모드를 선택하여 부호화를 한다. 따라서 코딩 모드들이 많아질수록 복잡도 역시 증가하며, 기존 표준보다 다양한 코딩모드를 지원하는 H.264에서는 복잡도가 더 많이 증가한다. 본 논문에서는 SAHTD(Sum of Absolute Hadamard Transform Difference)를 이용하여 화면 내 모드 결정부에서 빠른 화면내 모드 결정을 하면서도 압축 손실이 적게 발생하는 방법을 제시하였다. 휘도 신호 $16{\times}16$블록, 휘도 신호 $4{\times}4$블록, 색차 신호 $8{\times}8$블록 모두 SAHTD를 기준으로 최적의 모드가 결정된다. 휘도 신호 $16{\times}16$블록에서 SAHTD값에 따라 $4{\times}4$블록 부호화 과정을 조기 종결이 가능하게 하는 것과, 휘도 신호 $4{\times}4$에서는 SAHTD 값이 가장 낮은 3개의 모드와 MPM(Most Probable Mode)을 후보 모드로 선택하여 율-왜곡 최적화를 수행하는 방식이 사용되었다. MPM이 SAHTD값이 가장 낮을 경우 MPM이 휘도신호 $4{\times}4$블록의 최적의 모드로 선택되고 종료된다. JM 참조 소프트웨어를 통한 실험결과 제안된 기법은 기존 JM의 방식에 비해 화면 내 프레임의 부호화 시간의 84.7% 감소와 0.049dB의 PSNR 감소율, 0.595%의 비트 증가율을 보여주었다.

• Journal of Broadcast Engineering
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• v.16 no.3
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• pp.416-426
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• 2011

In this paper, we proposed an intra coding method with merging intra prediction mode to achieve intra coding gain. The proposed method uses signaling of prediction mode with merging prediction modes, which is different from the conventional method. If the number of blocks that has the same prediction mode compared to that to be predicted from neighboring blocks exceeds the predefined threshold, then the proposed method is used in order to reduce bits of intra prediction mode for coding efficiency. Otherwise the conventional method is used. Experimental results show the proposed method achieves the PSNR gain of about 0.05 dB in RD curve and reduces the bit rates about 1 % compared with H.264/AVC. In particular, the PSNR gain of about 0.1 dB in RD curve and reduces the bit rates about 1.7 % compared with H.264/AVC at low bit-rates. we can know that the proposed method is efficient tool at low bit-rates.