• ETRI Journal
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• 제30권5호
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• pp.729-734
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• 2008

Wireless communication systems, such as WLAN or Bluetooth receivers, employ preamble data to estimate the channel characteristics, introducing stringent settling-time constraints. This makes the use of traditional closed-loop feedback automatic gain control (AGC) circuits impractical for these applications. In this paper, a compact feedforward AGC circuit is proposed to obtain a fast-settling response. The AGC has been implemented in a 0.35 ${\mu}m$ standard CMOS technology. Supplied at 1.8 V, it operates with a power consumption of 1.6 mW at frequencies as high as 100 MHz, while its gain ranges from 0 dB to 21 dB in 3 dB steps through a digital word. The settling time of the circuit is below 0.25 ${\mu}s$.

• Transactions on Electrical and Electronic Materials
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• 제5권1호
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• pp.19-23
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• 2004

A novel method of high speed, accurate circuit simulation in 3-dimensional (3-D) parallel-plate capacitors is investigated. The basic concept of the circuit simulation methods is partial element equivalent circuit model. The three test structures of 3-D parallel-plate capacitors are fabricated by using multi-layer low-temperature co-fired ceramic (LTCC) process and their S-parameters are measured between 50 MHz and 5 GHz. S-parameters are converted to Y-parameters, for comparing measured data with simulated data. The circuit model parameters of the each building block are optimized and extracted using HSPICE circuit simulator. This method is convenient and accurate so that circuit design applications can be easily manipulated.

• 한국정보통신학회논문지
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• 제7권6호
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• pp.1103-1108
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• 2003

본 논문에서는 2.4GHz 대역의 근거리 무선 통신에 사용되는 역-F형 내부 안테나의 설계 값에 따른 안테나 특성을 분석하였다. PCB 기판에 인쇄된 형태로 설계하여 안테나의 길이, 단락 스터브의 두께, 피드선과 단락 스터브 사이의 간격, 안테나와 접지면 사이의 간격, 안테나의 두께 및 기판의 두께와 기판의 유전율에 따른 특성 변화를 연구하였다. 설계값에 따른 특성변화 그래프로부터 설계값을 튜닝하여 최적의 안테나를 설계하였다. 설계된 안테나는 VSWR이 1.5이하인 주파수 대역폭이 6.3%, 이득 3dB 정도를 얻었다.

• 한국통신학회논문지
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• 제27권3B호
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• pp.196-201
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• 2002

OFDM(Orthogonal Frequency Division Multiplex) 방식은 전통적인 단일 반송파 전송방식과는 달리 전송할 데이터를 병렬적으로 변조하여 주어진 다중전송채널에 다수의 반송파를 실어 보내므로 고속의 데이터전송을 수행하고 주파수를 직교적으로 오버랩시킴으로써 높은 스펙트럼 효율을 제공할 수 있어 LAN 및 WAN의 멀티미디어 분야에서 적용되고 있다. 본 논문에서는 컴퓨터 시뮬레이션을 통해서 변조방식에 따른 Coded-OFDM 무선통신시스템의 성능을 평가하였으며 코딩은 터보 코드를 사용하였고 변조방식으로서는 M-PSK나, M-QAM사용하였다. 시뮬레이션은 다중로 지연 확산, 가우시안채널잡음, Peak Power Clipping 등이 포함된 가상의 채널환경과 실제 채널환경에서 적용되었다. 시뮬레이tus 결과 3dB가량의 부호화 이득을 얻었고 Coded-OFDM 시스템에서의 변조방식으로는 M-QAM방식이 M-PSK방식보다 우수함을 확인하였다.

• 한국전자파학회논문지
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• 제13권5호
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• pp.459-467
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• 2002

5 GHz 대역의 무선 랜(LAN)용으로 크기가 작고 가벼우며 가격 이 싼 PIFA(Planar Inverted-F Antenna)를 설계한다. 질랜드(Zeland)사의 씨뮬레이션 툴인 IE3D를 사용하여 안테나를 설계하고 제작된 안테나의 측정결과를 분석한다. 제작된 안테나는 5.25 GHz에서 공진하고 정재파비가 1.5이하일 때 약 580 MHz의 대역폭을 갖는다.

• ETRI Journal
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• 제34권3호
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• pp.319-329
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• 2012

Closed-loop transmit diversity is considered an important technique for improving the link budget in the third generation and future wireless communication standards. This paper proposes several transmit diversity algorithms suitable for small wireless terminals and presents performance assessment in terms of average signal-to-noise ratio (SNR) and outage improvement, convergence, and complexity of operations. The algorithms presented herein are verified using data from measured indoor channels with variable antenna spacing and the results explained using measured radiation patterns for a two-element array. It is shown that for a two-element array, the best among the proposed techniques provides SNR improvement of about 3 dB in a tightly spaced array (inter-element spacing of 0.1 wavelength at 2 GHz) typical of small wireless devices. Additionally, these techniques are shown to perform significantly better than a single antenna device in an indoor channel considering realistic values of latency and propagation errors.

• 한국정보기술학회 영문논문지
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• 제8권2호
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• pp.147-157
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• 2018

In this study, we analyzed an outdoor visible light communication system and implemented it through a simulation. We designed a Reed-Solomon encoder, a variable interleaver structure, and set it to the Institute of Electrical and Electronics Engineers (IEEE) 802.15.7 PHY I specification mode. We also analyzed the performance of an additive white gaussian noise (AWGN) channel environment using a root-raised-cosine (RRC) filter, implemented a MATLAB simulation and analyzed its performance. The results showed a requirement for an additional signal-to-noise ratio (SNR) of approximately 1.5 dB in a 3-ray multipath visible light channel environment than in an AWGN environment.

• 한국전자파학회논문지
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• 제17권2호
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• pp.198-206
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• 2006

데이터 통신용 400 MHz ISM 대역 송${\cdot}$수신기를 설계하였다. 전파 법규의 8.5 kHz 이하 점유 주파수 대역폭을 만족하기 위해 GFSK 변조 방식을 이용하였고, 8051 CPU에 통신 프로토콜을 이식하여 데이터를 송${\cdot}$수신하였다. 제작된 송${\cdot}$수신기는 ${\pm}3\;kHz$이하의 주파수 변조도와 20 dB의 SINAD에서 -107 dBm의 감도를 나타내었으며, 인접 채널 평균 전력을 -60 dBc 이하로 전파 법규를 만족하였다. 제작된 송수신기의 BER 특성은 입력 신호 전력이 -110 dBm에서 $1.8{\times}10^{-3}$, -106 dBm 이상일 경우 0으로 측정되었다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.368-371
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• 2005

In this paper, a small band pass filter is designed using new probe type for wireless communication system. In order to provide a band pass filter which can be reduced in dimension, can be reduced in height, and can be surface-mounted. The filter was fabricated using $TE_{01{\delta}}$ mode dielectric resonator. The input/output probes are attached to coner portion of the rectangular metal cavity. Results of the manufactured filter$(12{\times}12{\times}8mm)$ show that the center frequency is 9.953GHz, the insertion loss is -2.98 dB, the 3dB-bandwidth is 15 MHz, and the lode Q is 663.

• International Journal of Internet, Broadcasting and Communication
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• 제13권1호
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• pp.54-60
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• 2021

AR (Augmented Reality) is a technology that provides virtual content to the real world and provides additional information to objects in real-time through 3D content. In the past, a high-performance device was required to experience AR, but it was possible to implement AR more easily by improving mobile performance and mounting various sensors such as ToF (Time-of-Flight). Also, the importance of mobile augmented reality is growing with the commercialization of high-speed wireless Internet such as 5G. Thus, this paper proposes a system that can provide AR services via GNN (Graph Neural Network) using cameras and sensors on mobile devices. ToF of mobile devices is used to capture depth maps. A 3D point cloud was created using RGB images to distinguish specific colors of objects. Point clouds created with RGB images and Depth Map perform downsampling for smooth communication between mobile and server. Point clouds sent to the server are used for 3D object detection. The detection process determines the class of objects and uses one point in the 3D bounding box as an anchor point. AR contents are provided through app and web through class and anchor of the detected object.