• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.10
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• pp.69-75
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• 2004

This work proposes an 8b 220 MS/s 230 mW 3-stage pipeline CMOS ADC with on-chip filers for temperature- and power- insensitive voltage references. The proposed RC low-pass filters improve switching noise performance and reduce reference settling time at heavy R & C loads without conventional off-chip large bypass capacitors. The prototype ABC fabricated in a 0.25 um CMOS occupies the active die area of 2.25 $\textrm{mm}^2$ and shows the measured DNL and INL of maximum 0.43 LSB and 0.82 LSB, respectively. The ADC maintains the SNDR of 43 dB and 41 dB up to the 110 MHz input at 200 MS/s and 220 MS/s, respectively, while the SNDR at the 500 MHz input is degraded as much as only 3 dB than the SNDR at the 110 MHz input.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.748-754
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• 2000

A novel single feed wide band CP stacked microstrip antenna using crossed slots has been designed, fabricated and measured. For the single rediating element the designed 10dB return loss bandwidth is 34.5%99.45~13.54 GHz), 3dB axial ratio bandwidth is 18.7%(11.17~13.39GHz), and 6 dB gain bandwidth is 29%(10.21~13.64GHz). For the 2$\times$2 array designed using a sequential rotation method, the 10dB return loss bandwidth is 35.9%(9.69~13.94GHz), 3dB axial ratio bandwidth is 34.6GHz (9.93~14.03GHz), and 6dB gain bandwidth is 27.4%(10.35~13.6GHz). For the fabricated 8$\times$8 array antenna, the 10dB return loss bandwidth is 27.3%(10.17~13.41GHz), 3dB axial ratio bandwidth is 27.9GHz(10.1~13.4GHz), and the radiation pattern is good agreement with theory. This antenna can be used for broadband applications for communications or broadcasting in Ku band.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.1-7
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• 2012

In this paper, An X-band solid state power amplifier(SSPA) for pulse compressed microwave signal with 60Watt power and power added efficiency(PAE) above 30% is described. Designed 60Watt high power amplifier(HPA) was implemented by cascade coupled amplifiers, and it is consisted on three stage drive amplifiers with internally matched GaAs FET and one stage main power amplifier with an internally matched GaN HEMT. The designed SSPA has performance with more than total power gain 37dB and output power 48dBm(60-W) in condition of frequency range $9.41{\pm}0.03GHz$, pulse period width under 1ms and duty cycle under 10%. The implemented SSPA can apply to high quality digital marine radar applications with pulse compression technique.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.254-254
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• 2010

기존의 부유게이트를 이용한 플래시 메모리는 소자의 크기를 줄이는데 한계가 있기 때문에 이를 해결하기 위한 비휘발성 메모리 소자로 CTF가 큰 관심을 받고 있다. CTF 메모리 소자는 기존의 플래쉬 메모리 소자에 비해 쓰고 지우는 속도가 빠르고, 데이터의 저장 기간이 길며, 쓰고 지우는 동작에 의한 전계 스트레스에 잘 견뎌내는 장점을 가지고 있다. 최근 터널 장벽의 두께와 종류를 변화시킨 소자의 전기적 특성을 향상하기 위한 연구들은 많이 있었지만, 터널 장벽의 적층구조 변화에 대한 연구는 비교적 적다. 본 연구에서는 터널 장벽의 적층구조 변화에 따른 CTF 메모리 소자의 프로그램 동작 특성 변화에 대해 관찰하였다. 기존의 단일 산화막 (silicon oxide; O) 대신 산화막과 higk-k 물질인 질화막 (silicon nitride; N)을 조합하여 ON, NON, ONO로 터널 장벽의 여러 가지 적층 구조를 가진 소자를 설계하여 각 소자의 프로그램 동작 특성을 조사하였다. CTF 메모리 소자의 프로그램 동작 특성을 거리와 시간에 따른 연속방정식, Shockley-Read-Hall 유사 트랩 포획 방정식 및 푸아송 방정식을 유한차분법을 사용하여 수치해석으로 분석하였다. WKB 근사를 이용하여 인가된 전계의 크기에 따라 터널링 현상에 의해 트랩층으로 주입하는 전자의 양을 계산하였다. 또한, 터널 장벽의 적층구조 변화에 따른 트랩층의 전도대역과 트랩층 내부에 분포하는 전자의 양을 시간에 따라 계산하였다. 계산 결과에서 터널 장벽의 적층구조 변화가 CTF 메모리 소자의 프로그램 동작 특성에 미치는 영향을 알 수 있었다. 소자의 프로그램 동작 특성을 분석함으로써 CTF 메모리 소자에 적합한 터널 장벽의 구조를 알 수 있었다. 기존의 단일 산화막보다 얇아진 산화막의 두께와 낮은 질화막의 에너지 장벽 높이로 전자의 터널링 현상이 더 쉽게 일어나기 때문에 ON 구조로 터널 장벽을 적층한 CTF 메모리 소자의 프로그램 속도가 가장 빠르게 나타났다. 이러한 결과는 터널 장벽의 구조적 변화가 전자의 터널 효과에 미치는 영향을 이해하고 프로그램 동작 속도가 빠른 CTF 메모리 소자의 최적화에 도움을 줄 수 있다.

• Journal of Advanced Navigation Technology
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• v.23 no.4
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• pp.309-315
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• 2019

This paper proposes an implementation of unequal power divider with 1:3 and 1:4 splitting ratio in multi-section structure using CPW and offset coupled transmission line. The power divider consists of a multi-section transmission line and a circuit with parallel capacitors and resistors. A multi-section transmission line was implemented by decomposing a ${\lambda}/4$ single transmission line terminated by an arbitrary impedance and converging it with a multi-section transmission line shorter than $90^{\circ}$ electrical length, and RC parallel circuits were connected between transmission lines to obtain reflection coefficient of output port and isolation characteristics between the output port. In this way, it was confirmed that the transmission lines at the unequal power divider designed at 2 GHz were shorter than ${\lambda}/4$ and implemented at least 27% less than the conventional ones, and that the broadband characteristics could be obtained.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.57.3-57.3
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• 2018

KVN 수신기는 22/43/86/129GHz 주파수 대역의 우주전파를 관측할 수 있는 4채널 동시 관측 시스템의 핵심으로 다수의 제어 및 모니터 항목이 존재한다. 대표적인 예로 Synthesizer, Pcal, LO, Vacuum, Cryogenic Temperature 등이 있으며 이와 관련된 여러 인스트루먼트가 21m 전파망원경의 하부단에 위치한 수신기실 내에 분산 배치되어 있다. 이에 대한 효율적인 제어를 위해서는 사용자 컴퓨터 관점에서 두 가지 조건이 충족되어야 한다. 첫째, 물리적으로 분산된 인스트루먼트에 대한 접근 및 변경이 용이해야 하고, 둘째는 단일 인터페이스 상에서 다양한 인스트루먼트를 하나로 통합하는 확장성이 보장되어야 한다. 이러한 요건을 고려하여 KVN은 산업 분야에서 널리 쓰이고 있는 프로피버스를 수신기 시스템의 제어를 위한 기반 인터페이스로 활용 중에 있고, 추가 기능 요구에 효율적으로 대처하고 있다. 본 발표에서는 먼저 KVN 수신기 시스템을 구성하는 인스트루먼트에 대해 살펴보고자 한다. 그리고 이를 효율적으로 제어하기 위한 기반 인터페이스로서 프로피버스 구축 및 활용 현황에 대해 논하고자 한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.9-18
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• 2021

The 5G communication system employs the millimeter wave with the extremely high frequency. Since the high frequency signal has the strong straightness, the beamforming technology based on the multiple base stations is required for services covering wide range. The beamformer needs the angle-of-arrival(AOA) information of the signal incident to the antenna, and it is generally estimated through the high resolution AOA estimation algorithm such as Multiple Signal Classification (MUSIC) or Estimation of Signal Parameters via Rotational Invariacne Technique (ESPRIT). Although various antenna array shapes can be employed for the beamformer, a single shape (square, circle, or hexagonal) is typically utilized. In this paper, we introduce a transmitting/receiving beamforming system based on the combined array antenna with square and circular shapes, which is proper to various frequency signals, and evaluate its performance. For evaluating the performance of the proposed beamforming system based on the combined array antenna, we implement the computer simulation employing various scenarios.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.2
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• pp.35-42
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• 2022

In this paper, a method to increase the combining efficiency and isolation of the combiner, the core module of SSPA (solid state amplifier), was studied. Specifically, the isolation was secured by matching the common port and the isolation port in the waveguide combiner. The matching structure for matching is in the form of a circular disk and is engraved inside the waveguide combiner. The structure is very simple, so it is possible to secure stable performance. And this structure showed more than 60 times higher critical power performance compared to previous studies, confirming that it is suitable for high output. And by combining 1-stage T-junction and 2, 3 stage MagicT combiner, miniaturization was achieved and the combining efficiency was optimized by reducing the insertion loss. The fabricated waveguide coupler obtained an isolation of 16dB or more and a coupling efficiency of 86.2%.

• Journal of Digital Policy
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• v.1 no.2
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• pp.53-59
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• 2022

In this paper, we proposed a method using sub-edge information extracted through a hierarchical structure in the process of generating super resolution based on a single image. In order to improve the quality of super resolution, it is necessary to clearly distinguish the shape of each area while clearly expressing the boundary area in the image. The proposed method assists edge information of the image in deep learning based super resolution method to create an improved super resolution result while maintaining the structural shape of the boundary region, which is an important factor determining the quality in the super resolution process. In addition to the group convolution structure for performing deep learning based super resolution, a separate hierarchical edge accumulation extraction process based on high-frequency band information for sub-edge extraction is proposed, and a method of using it as an auxiliary feature is proposed. Experimental results showed about 1% performance improvement in PSNR and SSIM compared to the existing super resolution.

• The Journal of the Acoustical Society of Korea
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• v.21 no.6
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• pp.566-575
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• 2002

Low-titrate audio coding enables a number of Internet and mobile multimedia streaming service more efficiently. For the help of next-generation mobile telephone technologies and digital audio/video compression algorithm, we can enjoy the real-time multimedia contents on our mobile devices (cellular phone, PDA notebook, etc). But the limited available bandwidth of mobile communication network prohibits transmitting high-qualify AV contents. In addition, most bandwidth is assigned to transmit video contents. In this paper, we design a novel and simple method for reproducing high frequency components. The spectrum of high frequency components, which are lost by down-sampling, are modeled by the energy rate with low frequency band in Bark scale, and these values are multiplexed with conventional coded bitstream. At the decoder side, the high frequency components are reconstructed by duplicating with low frequency band spectrum at a rate of decoded energy rates. As a result of segmental SNR and MOS test, we convinced that our proposed method enhances the subjective sound quality only 10%∼20% additional bits. In addition, this proposed method can apply all kinds of frequency domain audio compression algorithms, such as MPEG-1/2, AAC, AC-3, and etc.