• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.6-10
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• 2015

RF energy harvesting technology is a promising technology for generating the electrical power from ambient RF signal to operate low-power consumption devices(eg. sensor) in wireless communication networks. This paper, motivated by this and building upon existing CR(Cognitive Radio) network model, proposes a optimal control policy for RF energy harvesting CR networks model where secondary users that have low power consumption harvest ambient RF energy from transmission by nearby active primary users, while periodically sensing and opportunistically accessing the licensed spectrum to the primary user's network. We consider that primary users and secondary users are distributed as Poisson point processes and contact with their intended receivers at fixed distances. Finally we can derive the optimal frame duration, transmission power and density of secondary user from the proposed model that can maximize the secondary users's throughput under the given several conditions and suggest future directions of research.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.821-828
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• 2012

In this paper, we report that the differences between RF power levels can be improved in wavelength division multiplexing - radio over fiber (WDM-RoF) system by using a photonic crystal fiber. In a WDM-RoF system, each WDM channel experiences different received RF power level fluctuation in remote node (RN) because of wavelength-dependent dispersion. Since each WDM channel experiences different power fluctuation, the RF power fluctuation acts as a design constraint in viewpoint of network design. We designed a photonic crystal fiber to improve the effect of wavelength- dependent dispersion on RF power fluctuation. Also, we analyzed the wavelength-dependent difference of inter-channel RF power fluctuations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1A
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• pp.48-57
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• 2006

TWTA is to perform the function that amplifies the input RF signal and outputs it to the antenna. This paper proposes a method that is to improve the cathode ripple or the SHF TWTA for satellite communications. Through the embodiment and experiment of 600W SHF TWTA, this method satisfies the design specifications. Also, RF performance is improved by reducing the noise of auxiliary power sources supplied to the RF part and eliminating the unexpected noise. Therefore, this method is very effective and can be used to develop the similar equipments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.703-705
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• 2016

In this paper, we developed a wideband PIMD system to measure passive intermodulation distortion signals of mobile communication RF passive module. To represent wideband characteristic, we designed a receiver that meets low-noise and wideband characteristics in RF receiver. It allows high dynamic range in the RF receiver front end. In designed passive intermodulation distortion measurement system, we programed to display a PIMD signal with FPGA/DSP at PC. Implemented PIMD system was variable from 650 MHz to 2700 MHz and show up to -138 dB minimum detectable $3^{rd}$ passive inetrmodulation distortion signal.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.150-150
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• 2004

• Electronics and Telecommunications Trends
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• v.23 no.5
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• pp.131-142
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• 2008

최근 ITU-R에서는 전파혼신과 밀접한 관계가 있는 무선기기의 RF 항목(주파수허용편차, 점유주파수대역폭, 불요발사 등)에 대한 권고안 SM.1045, SM.328, SM.853, SM.329, SM.1539 등을 제정하거나 개정하였다. 이와 관련하여 본 논문에서는 국내 무선설비규칙의 전파 질 허용치 및 측정방법과 연계하여 ITU-R RF 성능 권고(안)의 핵심내용에 대한 분석결과를 제시하였다. 본 논문의 내용은 무선기기의 인증 및 무선국 검사에 적용되는 국내 무선설비 기술기준치를 이해하는 데 참고자료로 활용될 것으로 기대된다.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.124-127
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• 2005

국내에서는 언제 어디서나 휴대용 단말을 이용하여 저렴한 요금으로 고속의 무선인터넷을 사용할 수 있는 휴대인터넷 서비스를 2006년부터 서비스 할 계획이다. 앞으로 서비스 될 WiBro 휴대인터넷 서비스 방식은 기존 이동통신 방식과 달리 RF 송신 주파수와 수신 주파수가 동일한 TDD (time division duplexing) 방식을 사용한다. WiBro 무선통신 기지국 장비에 있어서도 기존 CDMA 이동통신 기지국 장비에서와 마찬가지로 RF Power Amplifier (PA)가 매우 고가의 핵심 부품이라 할 수 있다. 물론, 기존 FDD (frequency division duplexing) 방식의 CDMA 기지국 PA와 달리 WiBro용 기지국 PA는 TDD 신호를 처리할 수 있는 새로운 기술을 필요로 한다. TDD 방식인 WiBro 기지국용으로 사용할 수 있는 새로운 2.3 GHz 42 W PA를 설계, 제작한 결과를 본 논문에서는 발표하고자 한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1051-1057
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• 2009

USN(Ubiquitous Sensor Network) is used to provide many services such as bridge monitoring, cultural properties monitoring, river monitoring, protection of an old and feeble person, management and control of a city and circumstance monitoring, etc. A RF transceiver is needed for implementing USN. In this paper the implementation and the design of a RF transceiver for sensor nodes operating in 2.4GHz frequency band are presented. The design procedure of AGC, a receiver and a transmitter is described. And the performance of the implemented RF transceiver is also tested. The test results of receiver sensitivity, receiver dynamic range, frequency stability, phase noise, output power of transmitter, flatness and spectrum mask are presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.353-356
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• 2011

A Signal Receiving system to collect and analyze RF signals should be verified under simulated RF signal environment prior to verification on operation in fields and tested by using simulated RF signals in order to estimate its electrical performance. Generally, typical Signal Receiving system can measure, analyze frequency, pulse modulation, scan modulation, phase modulation on pulse, frequency modulation on pulse etc on RF signals. These RF signals should be generated from simulated RF sources in laboratory. Also the simultaneous RF signals should be simulated on laboratory. This paper describes the results of studying effective simulated RF signal source generation, the methods of the precise RF test signal generation in consideration of operational scenario.

• Electronics and Telecommunications Trends
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• v.34 no.5
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• pp.71-80
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• 2019

Gallium nitride (GaN) can be used in high-voltage, high-power-density/-power, and high-speed devices owing to its characteristics of wide bandgap, high carrier concentration, and high electron mobility/saturation velocity. In this study, we investigate the technology trends for X-/Ku-band GaN RF power devices and MMIC power amplifiers, focusing on gate-length scaling, channel structure, and power density for GaN RF power devices and output power level and output power density for GaN MMIC power amplifiers. Additionally, we review the technology trends in gallium arsenide (GaAs) RF power devices and MMIC power amplifiers and analyze the technology trends in RF power devices and MMIC power amplifiers based on both GaAs and GaN. Furthermore, we discuss the current direction of national research by examining the national and international technology trends with respect to X-/Ku-band power devices and MMIC power amplifiers.