• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.5
• /
• pp.920-927
• /
• 1994

A development of an efficient 14.0~14.5GHz 3 Watt SSPA is described in this paper, which is applicable to the very small aperture terminal(VSAT) for bidirectional data and voice signal transmission in low cost and with small size. The SSPA consists of two stages of low noise amplifiers using the low noise GaAs FETs. two stages of medium power amplifiers using the medium power GaAs FETs, and three stages of power amplifiers including a balanced amplifier using an internally matched power GaAs FET. The achieved with this seven stage amplifiers are 42dB signal power gain, 7dB noise figure, 35dBm output power at 1dB gain compression point and 2.0 and 1.5 input and output VSWR respectively.

• Proceedings of the KIEE Conference
• /
• 2003.07d
• /
• pp.2702-2704
• /
• 2003

본 논문은 전력선통신시스템 (Power Line Communications)을 위한 초고속 오류정정 부호화기 회로에 관한 설계방법론과 회로의 동작속도, 회로복잡성과 레이턴시에 직접적으로 기여하는 핵심 GF (Galois Field) 연산기들의 역할 및 이들의 설계결과에 관해 설명한다. 특히, 이러한 설계방법에 충실한 오류정정 부호화기회로는 입출력 병렬구조의 세미-시스톨릭 (Semi-systolic) 아키텍처를 갖는 고속의 내부 핵심 GF 연산기회로들을 채택함으로써 고속 연산을 가능토록 한다. 최적화된 GF곱셈연산기를 기반으로 설계되어진 리드-솔로몬 (Reed-Solomon) 오류정정 부호화기는 전력선 채널상에서 데이터를 전송 시 발생되는 연집오류들을 효과적으로 복원하도록 하는 대표적인 부호화기로 이미 존재하는 다른 회로들에 비해 동작속도, 회로의 복잡성, 및 레이턴시 측면에서 그 성능이 월등히 뛰어나므로, 실제 초고속 전력선 통신시스템의 설계 및 구현 시 효과적으로 이용될 수 있다.

• Journal of Power Electronics
• /
• v.19 no.3
• /
• pp.702-713
• /
• 2019

Multilevel Inverters (MLIs) are widely used in medium voltage applications due to their various advantages. In addition, there are numerous types of MLIs for such applications. However, the diode-less 3-level (3L) T-type Neutral Point Clamped (NPC) MLI is the most advantageous due to its low conduction losses and high potential efficiency. The power circuit of a 3L T-type NPC is derived by the conventional two level inverter by a slight modification. In order to explore the MLI performance for various Pulse Width Modulation (PWM) schemes, this paper examines the operation of a 3L (five level line to line) T-type NPC MLI for various types of Multi-Carriers Pulse Width Modulation (MCPWM) schemes. These PWM schemes are compared in terms of their voltage profile, total harmonic distortion (THD) and conduction losses. In addition, a 3L T-type NPC MLI is also compared with the conventional NPC in terms of number of switches, clamping diodes, main diodes and capacitors. Moreover, the capacitor-balancing problem is also investigated using the Neutral Point Fluctuation (NPF) method with all of the MCPWM schemes. A 1kW 3L T-type NPC MLI is simulated in MATLAB/Simulink and implemented experimentally and its performance is tested with a 1HP induction motor. The results indicate that the 3L T-type NPC MLI has better performance than conventional NPC MLIs.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.42 no.2
• /
• pp.444-452
• /
• 2017

Recently, a demand of Internet-of-things (IoT) rises dramatically and an interest in Low Power Wide Area (LPWA) grows larger accordingly. In this paper, performance in LoRa which is included in LPWA standard is analyzed. Particularly, after measuring Received Signal Strength Indication (RSSI) of received signal on Line-of-sight (LoS) and Non-line-of-sight (NLoS) environment and it is compared with RSSI which theoretical path loss model is applied to. Among many path loss models, the simulation for theoretical RSSI use Log-distance, Two-ray model and Okumura-Hata model that is based on the test database. Consequently, the result of Okumura-Hata model is the most similar with the measured RSSI. When a network based on LoRa is built, this result can used to decide optimal node arrangement.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2021.10a
• /
• pp.469-471
• /
• 2021

As wireless communication technology advances to ensure high accuracy and safety at high speeds, research and development of Visible Light Communication (VLC) technology has been accelerated as an alternative to traditional radio frequency (RF) technology. As the radio spectrum of RF communication becomes more congested and demand for bandwidth continues to increase, VLCs that can use unlicensed frequency band are proposed as a solution. However, VLC channels have broadcasting characteristics that make them easily exposed to eavesdropping and jamming attacks, and are vulnerable to MITM (Man-In-The-Middle) due to their line of sight (LOS) propagation characteristics. These attacks on VLC channels compromise the confidentiality, integrity, and availability of communications links and data, resulting in higher data retransmission rates, reducing throughput and increasing power consumption, resulting in lower data transmission efficiency. In this work, we model vulnerable VLC channels to analyze the impact of attacks and communications vulnerabilities by malicious jammers.

• Journal of Satellite, Information and Communications
• /
• v.7 no.2
• /
• pp.13-17
• /
• 2012

In recent years, type of the car is changing. Instead of cars that use internal combustion engines, we will use mainly eco-friendly electric vehicles. However, the utilization of electric vehicles brings enormous increase of power consumption. Thus, efficient power management and intelligent power consumption is required. Demand response can be effective measures of power consumption. In this paper, we present demand response technology applications, communication method, PLC application and simulation result.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2000.05a
• /
• pp.166-169
• /
• 2000

Chua's circuit is a simple electronic network which exhibits a variety of bifurcati on and attractors. The circuit consists of two capacitors, an inductor, a linear resistor, and a nonlinear resistor. In this paper, a transmitter and a receiver using two identical Chua's circuitsare proposed and a transmission secure communications are investigated. A secure communication method in which the desired information signal is synthesized with the chaos signal created by the Chua's circuit is proposed and information signal is demodulated also using the Chua's circuit. The proposed method is synthesizing the desired information with the chaos circuit by adding the information signal to the chaos signal in the power lime.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.8B
• /
• pp.1251-1258
• /
• 2010

Major utilities have been focusing on R&D and business of AMI system which plays a vital role in SmartGrid whose concept is to optimize energy efficiency with exchanging real time information between utilities and consumers based on IT technologies in power grid. In this paper, we introduce KEPCO's AMI business plan, the AMI System architecture, designed core devices, communication networks and value added services, and also explore technical and business characteristics of KEPCO's AMI system.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.7 no.8
• /
• pp.1933-1954
• /
• 2013

Multiple wireless devices are being widely deployed in Intelligent Transportation System (ITS) services on the road to establish end-to-end connection between vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) networks. Vehicular ad hoc networks (VANETs) play an important role in supporting V2V and V2I communications (also called V2X communications) in a variety of urban environments with distinct topological characteristics. In fact, obstacles such as big buildings, moving vehicles, trees, advertisement boards, traffic lights, etc. may block the radio signals in V2X communications. Their impact has been neglected in VANET research. In this paper, we present a realistic and efficient radio propagation model to handle different sizes of static and moving obstacles for V2X communications. In the proposed model, buildings and large moving vehicles are modeled as static and moving obstacles, and taken into account their impact on the packet reception rate, Line-of-sight (LOS) obstruction, and received signal power. We use unsymmetrical city map which has many dead-end roads and open faces. Each dead-end road and open faces are joined to the nearest edge making a polygon to model realistic obstacles. The simulation results of proposed model demonstrates better performance compared to some existing models, that shows proposed model can reflect more realistic simulation environments.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.17 no.4
• /
• pp.187-192
• /
• 2017

Rigorous longitudinal modal transmission-line theory (L-MTLT) is applied to analyze maximum power transfer in asymmetric grating-assisted directional couplers(A-GADC). By defining a coupling efficiency amenable to rigorous analytical solutions and interference between symmetric and asymmetric supermodes, the power exchange of TE modes as a function of propagation distance is numerically evaluated. The numerical result reveals that maximum power transfer occurs at a grating period ${\Lambda}_{eq}$, in which the insertion loss of supermodes is equal to each other. That is, it is generally different from conventional phase-matching condition of GADC. Furthermore, as the asymmetric profile of grating change to symmetrical profile, the coupling length decreases and the coupling efficiency for power transmission increases.