• Title, Summary, Keyword: RF Transmission

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A Study on Minimization of Train Delays and Train Operation Interruptions by RF Transmission System. (RF 통신시스템을 이용한 열차 운행중단 및 열차 지연의 최소화에 관한 연구)

  • Lee, We-Jae;Kook, Kwaung-Ho
    • Proceedings of the KSR Conference
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    • pp.1466-1472
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    • 2008
  • To minimize the train operation interruptions and train exchanges, the RF transmission system is proposed. The current control room of the Seoul Metro has information of the train movement through the Total Traffic Control System, but it does not have information of the train itself, rail status, and other facilities' status. When some trouble occurs during train operation, the train crews should report the control room about the trouble and fix it. If the control room has exact information of the trouble, the expert in the control room can help the crews to fix the trouble swiftly and exactly. Since the crews are busy taking care of the trouble, they often miss to report the control room on time. The proposed RF transmission system relays the information of the train to the control room automatically in real time, and makes it possible to provide the passengers good service by reducing the train operation interruptions and train exchanges.

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Performance Analysis of Optical SCM Link System for CDMA RF Signal Transmission (CDMA RF 신호 전송을 위한 SCM 광링크 시스템의 성능분석)

  • 유진태
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.9B
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    • pp.1542-1550
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    • 2000
  • Fiber optic link systems based on SCM scheme are widely used as efficient and economic RF signal links between base station and a central station in mobile communication networks. However, its performance can be seriously limited depending on the operational conditions of not only the optical transmission system but also the wireless link in various environments. In this paper, we propose an analytic model for performance analyses of the SCM fiber optic link for CDMA RF signal transmission in various link environments. We present optimal operational conditions taking account of the nonlinear effects of the optical transmission system, and the multiple access interference produced at the wireless link. It has been shown through the BER analyses in this paper that the selection of optical modulation index of the SCM fiber optic links can be found optimally to minimize the fiber optic link noises and intermodulation distortion due to LD.

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A Novel Design of an RF-DC Converter for a Low-Input Power Receiver

  • Au, Ngoc-Duc;Seo, Chulhun
    • Journal of electromagnetic engineering and science
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    • v.17 no.4
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    • pp.191-196
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    • 2017
  • Microwave wireless power transmission (MWPT) is a promising technique for low and medium power applications such as wireless charging for sensor network or for biomedical chips in case with long ranges or in dispersive media such. A key factor of the MWPT technique is its efficiency, which includes the wireless power transmission efficiency and the radio frequency (RF) to direct current (DC) voltage efficiency of RF-DC converter (which transforms RF energy to DC supply voltage). The main problem in designing an RF-DC converter is the nonlinear characteristic of Schottky diodes; this characteristic causes low efficiency, higher harmonics frequency and a change in the input impedance value when the RF input power changes. In this paper, rather than using harmonic termination techniques of class E or class F power amplifiers, which are usually used to improve the efficiency of RF-DC converters, we propose a new method called "optimal input impedance" to enhance the performance of our design. The results of simulations and measurements are presented in this paper along with a discussion of our design concerning its practical applications.

B1+ Comparison for Different RF Coils at 7 T MRI (7 T MRI에서의 다양한 RF 코일에 대한 B1+ 비교)

  • Kim, Hong-Joon;Yoo, Hyoung-Suk
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.23 no.8
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    • pp.1010-1013
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    • 2012
  • This paper demonstrates the use of the convex optimization to localize the transverse magnetic $B_1^+$ field in regions of interest for recently proposed multi-sectioned alternating impedance coils and the traditional transmission line coil. An approach based on different axial slices to identical RF coils except upper stripline structure is investigated. Electromagnetic simulation results are compared for RF coils and discussed in detail at 7.0 T.

Comparative Study on the Power Transfer Efficiency of Magnetic Resonance and Radio Frequency Wireless Power Transmission

  • Kim, Ye-Chan;Choi, Bo-Hee;Lee, Jeong-Hae
    • Journal of electromagnetic engineering and science
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    • v.16 no.4
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    • pp.232-234
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    • 2016
  • In this paper, the power transfer efficiencies (PTEs) of magnetic resonance (MR) wireless power transmission (WPT) and radio frequency (RF) WPT are compared as a function of the distances between resonators (or antennas). The PTE of the C-loaded loop resonators during MR WPT was theoretically calculated and simulated at 6.78MHz, showing good agreement. The PTE of the patch antennas, whose area is the same as the C-loaded loop resonator during MR WPT, was theoretically calculated using the Friis equation and the equation by N. Shinohara and simulated at 5.8 GHz. The three results from the Friis equation, the equation by N. Shinohara, and from a full wave simulation are in strong agreement. The PTEs, when using the same size resonators and antennas are compared by considering the distance between the receiver and transmitter. The compared results show that the MR WPT PTE is higher than that of the RF WPT PTE when the distance (r) between the resonators (or antennas) is shorter. However, the RF WPT PTE is much higher than that of the MR WPT PTE when the distance (r) between the resonators (or antennas) is longer since the RF WPT PTE is proportional to $r^{-2}$ while the MR WPT PTE is proportional to $r^{-6}$.

A Study on Characteristics of the Transmission Line Employing Periodically Perforated Ground Metal on GaAs MMIC and Its Application to Highly Miniaturized On-chip Impedance Transformer Employing Coplanar Waveguide (GaAs MMIC상에서 주기적으로 천공된 홀을 가지는 접지 금속막 구조를 이용한 전송선로 특성연구 및 코프레너 선로를 이용한 온칩 초소형 임피던스 변환기에의 응용)

  • Yun, Young
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.8
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    • pp.1248-1256
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    • 2008
  • In this paper, basic characteristics of transmission line employing PPGM (periodically perforated ground metal) were investigated using theoretical and experimental analysis.According to the results, unlike the conventional PBG (photonic band gap) structures, the characteristic impedance of the transmission line employing PPGM structure showed a real value, which exhibited a very small dependency on frequency. The transmission line employing PPGM structure showed a loss (per quarter wave length) higher by $0.1{\sim}0.2\;dB$ than the conventional microstrip line. According to the investigation of the dependency of RF characteristic on ground condition, the RF characteristic of the transmission line employing PPGM structure was hardly affected by the ground condition in the frequency lower than Ku band, but fairly affected in the frequency higher than Ku band, which indicated that coplanar waveguide employing PPGM structure was optimal for RF characteristic and reduction of size. Considering above results, impedance transformer was developed using coplanar waveguide with PPGM structure for the first time, and good RF characteristics were observed from the impedance transformer. In case that {\lambda}/4$ impedance transformer with a center frequency of 9 GHz was fabricated for a impedance transformation from 20 to10 {\Omega}$, the line width and length were 20 and $500\;{\mu}m$, respectively, and its size was only 0.64 % of the impedance transformer fabricated with conventional microstrip lines. Above results indicate that the transmission line employing PPGM is a promising candidate for a development of matching and passive elements on MMIC.

Design and Fabrication of Rectenna for Microwave Wireless Power Transmission (마이크로파 무선전력전송을 위한 렉테나 설계와 구현)

  • Park, Jeong-Heum
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.6
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    • pp.43-48
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    • 2006
  • In this paper, the rectenna converting 2.45[GHz] microwave into DC power is designed and fabricated for wireless power transmission using microwave and the methode for impedance matching and tuning are proposed in order to maximize RF-DC conversion efficiency. The fabricated rectenna can be easily tuned by using a broad open stub and has the RF-DC conversion efficiency up to 59[%] when the 5[dBm] input power is applied. The 2.2[V], 1.5[mW] DC level, in the 1[m] distance between the transmitter and the receiver can be obtained and this value is avaliable in the small power digital system.

A Study of Interference on Underground Tunnel in Radio Frequency-Communication Based Train Control System (무선 통신기반 열차제어시스템의 지하구간 전파간섭에 대한 연구)

  • Noh, Young-Un;Lee, Jong-Woo
    • Proceedings of the KSR Conference
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    • pp.1370-1378
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    • 2008
  • In the system necessary for safety such as the train control system, to make train control information be sent correctly is very important. In the case of the system such as RF-CBTC(Radio Frequency-Communication Based Train Control), sometimes failure in correctness of train controlling information may happen because the information is sent throughout wireless transmission between on-board system of a train and wayside transmitter, and then, it is exposed to noises. Of RF-channel interference, there are various forms. Under the environment of mobile telecommunications, adjacent-channel interference and Co-channel interference are in trouble, and under the environment of the wireless LAN, inter-symbol interference is in trouble. Also, the system of the cellular CDMA mobile telecommunication is affected on the RF-channel interference such as Doppler effect, multi-cell interference, and other users' intervention. In this paper, we analyzed the effect of the train control information related to fading, intervention and other noises made in the underground interval and explained the transmission characteristics numerically. Furthermore, we calculated the mean of the error terms by increasing users in the system of the cellular CDMA. As the method for decrease the error term of sent information, we represented the way adjusting the arrangement of antennas, and we did the model related to the system of RF-CBTC in which the location of an antenna is calculated with really measured value of the transmission characteristics and the way confirming reliability of the wireless transmission.

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Performance Analysis of DS-CDMA Signal through MZ Modulator in optical SCM Signal Transmission (광 SCM 전송방식에서 MZ 변조기를 통과한 DS-CDMA 신호의 성능분석)

  • 김회준;임명섭
    • Proceedings of the IEEK Conference
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    • pp.77-80
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    • 2001
  • In this paper, it is analyzed the statistical characteristics on the transmission performance of the optical SCM transmission in the CDMA RF signal relay system. Using Mach-Zehnder modulator, optical signal is regenerated into CDMA RF signal. Transfer function model of mach-Zehnder modulator is approximated to the third power of the input signal using Taylor series. BER results are analyzed under the multiple access interference and multi-path fading environment.

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A study on RF characteristics of fishbone-type transmission line on PES substrate for application to flexible wireless communication device (플렉시블 무선통신소자 응용을 위한 PES 박막상의 Fishbone 형태의 전송선로에 대한 RF 특성연구)

  • Yun, Young
    • Journal of Advanced Marine Engineering and Technology
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    • v.38 no.3
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    • pp.302-311
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    • 2014
  • In this work, a FTTL (fishbone-type transmission line) structure was fabricated on PES (polyether sulfone) for a realization of transparent flexible wireless communication device, and its RF characteristics were investigated. According to the results, the FTTL on PES showed a short wavelength characteristic compared with conventional coplanar waveguide. Concretely, the wavelength of the FTTL was 2.23 mm at 50 GHz, which was 56.6 % of the conventional coplanar waveguide. According to the bandwidth extraction result, the passband of the FTTL on PES was 608 GHz. Unlike conventional periodic structures, the characteristic impedance of the FTTL on PES showed a very low frequency dependency, which means that the FTTL on PES can be used for application to transmission line and distributed passive components with a broadband operation frequency.