• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1565-1573
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• 2001

In order to resolve problems according to the phase error in QPSK demodulator in the digital satellite broadcasting, the demodulator requires carrier recovery loop which searches for the frequency and phase of the carrier. In this paper the drawback of NCO of the conventional carrier recovery loop is to wastes a amount of power for the structure of Look-up table , we designed the structure of combinational logic without the Look-up table. In the comparison with dynamic power of the proposed NCO, the power of NCO with the Look-up table is 175[${\mu}$W], NCO with the proposed structure is 24.65[${\mu}$W]. As the result, it is recognized that loss power is reduced about one eighth. In the simulation of carrier recovery loop designed QPSK demodulator, it is known that the carrier phase is compensated.

• ETRI Journal
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• v.43 no.3
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• pp.389-399
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• 2021

In this paper, we propose one-bit feedback-based distributed beamforming (DBF) techniques for simultaneous wireless information and power transfer in interference channels where the information transfer and power transfer networks coexist in the same frequency spectrum band. In a power transfer network, multiple distributed energy transmission nodes transmit their energy signals to a single energy receiving node capable of harvesting wireless radio frequency energy. Here, by considering the Internet-of-Things sensor network, the energy harvesting/information decoding receivers (ERx/IRx) can report their status (which may include the received signal strength, interference, and channel state information) through one-bit feedback channels. To maximize the amount of energy transferred to the ERx and simultaneously minimize the interference to the IRx, we developed a DBF technique based on one-bit feedback from the ERx/IRx without sharing the information among distributed transmit nodes. Finally, the proposed DBF algorithm in the interference channel is verified through the simulations and also implemented in real time by using GNU radio and universal software radio peripheral.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.6
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• pp.129-135
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• 2022

In this paper, a 100 W SSPA in Ka-band was developed by combining 16 GaN MMICs which were 10 W amplifiers, respectively. The gate voltage of SSPA was controlled to minimize the effect of SSPA noise on the receiver during the receiving time. And the transmit power could be reduced about 20 dB to prevent the receiver from being saturated by a large signal from a nearby target. At 10%, 40% duty rato, the peak power and the power efficiency at center frequency were measured 52.4 dBm, 19.2%, and 51.6 dBm, 16.6% respectively.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.1
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• pp.58-62
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• 2007

Digital communication is important for reliability and mobilization of the multi-channel communication systems. Transmitting and receiving data for the mobilization should be possible in anywhere and in anytime. And this system must be designed light weight small size and low power. One are essential technology for implementing the mobile wireless communication system on the age of ubiquotos. Requirements in constructing such communication field are followings. At first data transmitting and receiving should be carried out by a simple command. Second, the device should be designed as hand-hold type and low power consumption. Third, data communication should be reliable. As one of examples, car to car system which is popular in the market is introduced here, All traffic information in highway is transmitted from one car to another by using this system which can prevent possible traffic accident. This paper shows the design of a digital data communication system with CC1020 chip. This CC1020 makes easy frequency selection and easy switch from the transmit mode to the receive mode by simple setting of a memory register in the chip. The transmit power of this system is designed 10dBm and its communication range is about 100m. The power supplied this system is 3V considered as low power. The sleep mode can be easily entered during transmit mode or receive mode. We shows the program algorithm of CC1020 and interface circuit between MCU and CC1020. We shows the Photo of the CC1020 Module and Atmega128 Module.. We analysed the receiver rate with this system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.4
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• pp.119-125
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• 2022

The power supply for the anti-aircraft radar homing sensor should allow the system to receive power quickly and stably without the influence of noise. For this purpose, DC-DC converters are widely used for reliable power conversion. Also, switching of DC-DC converters Frequency noise should not cause false alarms and ghosts that may affect the detection and tracking performance of the system, and it should have a check function that can monitor power in real time while the homing sensor is operating. In order to apply to anti-aircraft radar homing sensor, we developed a multi-output switching power supply with maximum output 𐩒𐩒𐩒 W, efficiency 80% or more (@100% load), output power by receiving 28VDC input, and power supply to achieve more than 80% efficiency. A DC-DC converter was applied to this large output, and the multi-output flyback method was applied to the rest of the low-power output.

• Bulletin of the Korea Photovoltaic Society
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• v.3 no.1
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• pp.61-67
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• 2017

Concentrated solar power(CSP) is receiving attention for its ability to generate dispatchable power from heat stored in thermal energy storage(TES). There are currently four types of CSP technology, however experts expect that only parabolic trough and solar tower are to survive from the market due to its higher efficiency and larger capacity in storage. While the initial cost for installing CSP plant is still expensive, the experts expect that investment cost of CSP would decline to the level which would be competitive with PV or wind in the near term future. In addition, further growth in its installation capacity is expected due to the United States and China's aggressive investments in CSP.

• Journal of Power System Engineering
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• v.9 no.2
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• pp.45-49
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• 2005

Liquefied natural gas takes up six hundredths of the volume of natural gas, which makes storage and transportation much easier. To send out natural gas via a pipeline network across the nation, high-pressure LNG pumps supply highly compressed LNG to high-pressure vaporization facilities. The Number of high-pressure LNG pumps determined the send-out amount in LNG receiving terminal. So it is main equipment at LNG production process and should be maintained on best conditions. In this paper, to find out the cause of high beat vibration at cryogenic pumps, vibration and motor current signal analysis have been performed. High vibration of cryogenic pumps could be reduced due to the modification of motor rotor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.109-121
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• 2010

Recently, smart grid for solving energy problems have been receiving growing attention. Also, renewable energy sources such as photovoltaic and fuel cell as future energy for realizing smart grid have been widely studied. On the other hand, hybrid structures have been proposed since the output power of these renewable energy sources is usually dependent on weather conditions. This paper proposes a hybrid system involving a proper photovoltaic in the hybrid system, Polymer Elecrolyte Membrane Fuel Cell with water electrolyzer and ultracapacitor. The results of simulation and output of the proposed model are established and analysed by Matlab/Simulink and SimPowerSystems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.3
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• pp.224-229
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• 2004

In order to control the railway noise, the radiation characteristic of the noise when the train passes by should be analyzed. Generally, the major noise sources of the Korea Train Express are the rolling noise and power unit noise up to 300km/h. In this paper, a train model that is considered to be a row of point sourcesis introduced to analyze the radiation characteristic. The analysis results are compared with the measurement ones. It is shown that the propagation characteristic of the rolling noise is a dipole type and the noise generated by the power unit is radiated as a cosine type. With increasing of the train speed, the noise level at a receiving point is increased in the direction of motion and reduced in the direction opposite to the motion. The analysis results including the moving effect of the noise source at 300km/h show good agreement with the measurement results.

• Journal of Environmental Impact Assessment
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• v.16 no.1
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• pp.99-105
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• 2007

Since 1990s, the railway noise has been researched and developed in our nation. First of all, what's causing the noise and how to eliminate the cause of the noise must be found out. Secondly, cutting off the propagation path of the noise from the noise source to the receiving points. In this study the characteristics of prediction formula for the assessment of railway noise used in some nations including Korea were investigated. In order to develop the prediction formula of the railway noise, the noise radiated from railway vehicle, rails and sleepers, characteristics of noise barrier, velocity of train, ground effects, roughness should be analyzed and predicted. Especially, on the basis of acoustics, the characteristics of source are applied to acoustic power and directivity information.