• 한국컴퓨터정보학회논문지
• /
• 제23권1호
• /
• pp.1-7
• /
• 2018

The Korean Air Force FA-50 aircraft currently operating in the Air Force is using Ultra High Frequency (UHF) frequency communications for navigation communications with ground control stations or other aircraft. The pilot communicates by changing frequency at any time during flight, and performs communication by directly inputting from the Integrated Up-Front Controller installed in the cockpit. The frequency is designated as secret, and the pilot receives the task with the frequency channel number (001~xxx) and finds the frequency of the channel in the list of 4,000 frequency channels and inputs it manually. This reduces the safety and convenience of pilots' operations and exposes them to hazards that may occur especially during night flight missions. In this paper, we propose a function to embed the frequency corresponding to the frequency channel list in IMDC, the aircraft mission computer, and to automatically change the frequency when the pilot only inputs the channel number.

• 한국통신학회논문지
• /
• 제41권2호
• /
• pp.254-262
• /
• 2016

차량용 레이더 시스템에 대한 수요가 증가함에 따라서, 상호 간섭 문제는 차량 안전을 보장하기 위해 해결해야 할 결정적인 이슈가 되었다. Frequency modulated continuous wave(FMCW) 레이더의 상호 간섭은 잡음 전력 증가의 형태로 나타나며, 이는 간섭체로 인한 타겟 검출의 실패로 이어진다. 기존의 FMCW 레이더의 주파수 추정을 위하여 사용되는 fast Fourier transform (FFT) 기법은 차량용 레이더 간섭 환경에서는 취약하다. 이러한 단점을 극복하기 위하여, 본 연구에서는 간섭환경에서 사용하기 위한 고해상도 주파수 추정 기법을 제안한다. 제안된 알고리즘의 성능을 입증하기 위하여, 77GHz 전방 감시용FMCW 레이더 시스템을 도입하였다. 제안된 기법은 간섭환경에서도 정확하게 주파수를 추정할 수 있는 multiple signal classification, estimation of signal parameters via rotational invariance techniques과 같은 고해상도 알고리즘을 이용한다. 실험결과로부터 제안된 알고리즘이 기존의 FFT 알고리즘에 비해 신호 대 간섭비 측면에서 14 dB 이상의 마진을 가짐을 확인하였다.

• ETRI Journal
• /
• 제29권5호
• /
• pp.569-595
• /
• 2007

Particularly in wireless communications, link errors severely affect the quality of the services due to the high error probability and the specific error characteristics (burst errors) in the radio access part of the network. In this work, we show that thorough analysis and appropriate modeling of radio-link error behavior are essential to evaluate and optimize higher layer protocols and services. They are also the basis for finding network-aware cross-layer processing algorithms which are capable of exploiting the specific properties of the link error statistics, such as predictability. This document presents the analysis of the radio link errors based on measurements in live Universal Mobile Telecommunication System (UMTS) radio access networks as well as new link error models originating from that analysis. It is shown that the knowledge of the specific link error characteristics leads to significant improvements in the quality of streamed video by applying the proposed novel network- and content-aware cross-layer scheduling algorithms. Although based on live UMTS network experience, many of the conclusions in this work are of general validity and are not limited to UMTS only.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
• /
• pp.405-409
• /
• 2004

We chose the Kushiro wetland in Hokkaido, Japan, as a test site to monitor wetland areas. Synthetic aperture radar (SAR) can carry out continuous observation in any weather conditions, and can therefore be used to observe high humidity areas such as wetlands. We applied multi-parameter SAR data (dual-frequency, multi-polarization, and multi-incidence angle) to monitoring the wetland forest. To find the optimum incidence angle and polarization for monitoring the wetland biomass, a simple backscattering model of wetland vegetation was developed and applied to estimate backscattering coefficients for different biomass and surface conditions.

• ETRI Journal
• /
• 제43권2호
• /
• pp.209-220
• /
• 2021

The filtered orthogonal frequency division multiplexing (F-OFDM) system has been recommended as a waveform candidate for fifth-generation (5G) communications. The suppression of out-of-band emission (OOBE) and asynchronous transmission are the distinctive features of the filtering-based waveform frameworks. Meanwhile, the high peak-to-average power ratio (PAPR) is still a challenge for the new waveform candidates. Partial transmit sequence (PTS) is an effective technique for mitigating the trend of high PAPR in multicarrier systems. In this study, the PTS technique is employed to reduce the high PAPR value of an F-OFDM system. Then, this system is compared with the OFDM system. In addition, the other related parameters such as frequency localization, bit error rate (BER), and computational complexity are evaluated and analyzed for both systems with and without PTS. The simulation results indicate that the F-OFDM based on PTS achieves higher levels of PAPR, BER, and OOBE performances compared with OFDM. Moreover, the BER performance of F-OFDM is uninfluenced by the use of the PTS technique.

• Journal of Communications and Networks
• /
• 제9권1호
• /
• pp.34-42
• /
• 2007

Orthogonal frequency division multiplexing (OFDM) combined with time division multiplexing (TDM), in this paper called OFDM/TDM, can overcome the high peak-to-average-power ratio (PAPR) problem of the conventional OFDM and improve the robustness against long time delays. In this paper, the bit error rate (BER) performance of OFDM/FDM in a frequency-selective Rayleigh fading. channel is evaluated by computer simulation. It is shown that the use of frequency-domain equalization based on minimum mean square error criterion (MMSE-FDE) can significantly improve the BER performance, compared to the conventional OFDM, by exploiting the channel frequency-selectivity while reducing the PAPR or improving the robustness against long time delays. It is also shown that the performance of OFDM/FDM designed to reduce the PAPR can bridge the conventional OFDM and single-carrier (SC) transmission by changing the design parameter.

• Journal of electromagnetic engineering and science
• /
• 제8권3호
• /
• pp.119-128
• /
• 2008

In this paper, we propose a developing approach of 600 W super high frequency(SHF) traveling wave tube amplifier (TWTA) for communications. Also, we make a TWTA called the experimental-TWTA(ETWTA), which uses a cathode ripple reduction technique to improve RF performance. After implementation, we discuss, and compare it with some other TWTAs. Its RF performance is better than that of other TWTAs. Therefore, this methodology can be used to develop the high power SHF TWTA for communications.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
• /
• pp.115-118
• /
• 2007

Luminous efficacy of 6.0 lm/W has been realized by introducing a spatial positive column discharge together with delayed D pulses, shared sustain pulse voltage, and low sustain frequency drive. Also a high speed addressing of $0.25{\mu}s$ was achieved. The luminance was $157cd/m^2$, which is high enough for a 260-in. FHD display.

• 한국전자파학회논문지
• /
• 제29권1호
• /
• pp.10-19
• /
• 2018

본 논문에서는 고주파 Radio-Frequency Interference (RFI) 측정용 프로브로 널리 쓰이는 Printed Spiral Coil(PSC)의 고주파 등가회로 모델이 제안되었다. 제안된 모델은 고주파 정합성을 확보하기 위하여 PSC의 설계변수에 기반한 분포 모델로 설계되었으며, 제안된 분포 등가회로 모델을 바탕으로 T-Pi 등가변환을 이용한 PSC의 고주파 해석적 모델 역시 새로이 제안되었다. 제안된 모델의 실제 고주파 RFI 측정 시 효용성을 확인하기 위하여, 임의의 RFI 노이즈 원으로 설계된 마이크로스트립 라인과 PSC 사이의 전달함수를 제안된 모델과 상호 인덕턴스를 결합하여 추출하였다. 제안된 PSC 모델의 자기 임피던스(self-impedance)와 전달함수는 3-dimensional field solver를 이용한 시뮬레이션 및 실 측정으로 검증되었으며, 6 GHz까지 높은 정합성을 보이는 것이 확인되었다. 제안된 PSC의 자기 임피던스 및 전달함수 모델은 GHz 영역의 고주파 통신대역에서의 RFI 측정용 프로브 설계 및 노이즈 간섭 예측에 활용될 수 있다.

• ETRI Journal
• /
• 제35권3호
• /
• pp.397-405
• /
• 2013

In this paper, two sets of spectrally efficient ultra-wideband (UWB) pulses using zinc and frequency-domain Walsh basis functions are proposed. These signals comply with the Federal Communications Commission (FCC) regulations for UWB indoor communications within the stipulated bandwidth of 3.1 GHz to 10.6 GHz. They also demonstrate high energy spectral efficiency by conforming more closely to the FCC mask than other UWB signals described in the literature. The performance of these pulses under various modulation techniques is discussed in this paper, and the proposed pulses are compared with Gaussian monocycles in terms of spectral efficiency, autocorrelation, crosscorrelation, and bit error rate performance.