• Journal of information and communication convergence engineering
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• v.13 no.4
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• pp.241-247
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• 2015

Cognitive radio has been attracting increased attention as an effective approach to improving spectrum efficiency. One component of cognitive radio, spectrum sensing, has an important relationship with the performance of cognitive radio. In this paper, after a summary and analysis of the existing spectrum-sensing algorithms, we report that the existing eigenvalue-based semi-blind detection algorithm and blind detection algorithm have not made full use of the eigenvalues of the received signals. Applying multi-antenna systems to cognitive users, we design a variety of spectrum-sensing algorithms based on the joint distribution of the eigenvalues of the received signal. Simulation results validate that the proposed algorithms in this paper are able to detect whether the signal of the primary user exists or not with high probability of detection in an environment with a low signal-to-noise ratio. Compared with traditional algorithms, the new algorithms have the advantages of high detection performance and strong robustness

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.28-34
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• 2002

Irregular reflected signals on a sea surface make clutters to a ship's radar image. Clutters are similar to Gaussian white noises which are very harmful for detecting objecting at sea by a ship's radar. To remove the clutter effects, many papers show the algorithms by antenna, filters, and so on. This paper shows a new algorithm which uwes Wavelet and Morphology median filter conceps for removing clutter and enhancing image in order to detect well a distressed of being rescued ship in a rough weather condition at sea.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.470-474
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• 2006

This dissertation discuses about a ferrite core plasma source using low operating frequency without sputtering problem by the stored electric field. Compared with the conventional RF power system with 13.56MHz switching frequency, the proposed plasma power system is only separated at 400kHz, so that it makes possible to use of low cost switching elements, PWM control and soft switching. Moreover, it could improve the coupling efficiency for plasma and antenna by using the ferrite core in order to transfer the energy of the load This dissertation tried to analyze new plasma generation method for the plasma generation system by modeling the plasma load and grafting the concept of impedance matching in order to interpret it with the formula This dissertation verified the ferrite core inductive coupling plasma source authorized for 400kHz of low frequency power by applying to the semi-conductor ash process thru the measurement of ash capacity and uniformed plasma distribution on the actual wafer.

• Journal of Astronomy and Space Sciences
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• v.19 no.3
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• pp.197-206
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• 2002

NORAD Two Line Elements (TLE) are widely used for the increasing number of small satellite mission operations and analysis. However, due to the irregular periodicity of generation of the NORAD TLE, a new TLE that is independent of NORAD is required. A TLE type Orbit Determination (TLEOD) has been developed for the generation of a new TLE. Thus, the TLEOD system can provide an Antenna Control Unit (ACU) with the orbit determination result in the type of a TLE, which provides a simple interface for the commercialized ACU system. For the TLEOD system, NORAD SGP4 was used to make a new orbit determination system. In addition, a least squares method was implemented for the TLEOD system with the GPS navigation solutions of the KOMPSAT-1. Considering both the Orbit Propagation (OP) difference and the tendency of $B^{*}$ value, the preferable span of the day in the observation data was selected to be 3 days. Through the OD with 3 days observation data, the OP difference was derived and compared with that of Mission Analysis and Planning (MAPS) for the KOMPSAT-1. It has the extent from 2 km after sit days to 4 km after seven days. This is qualified enough for the efficiency of an ACU in image reception and processing center of the KOMPSAT-2.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.4
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• pp.1-7
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• 2011

In this paper, we design rectifing circuits at 910MHz, which is used for passive RFID system, for wireless power transmission system by using two types of schottkey diodes HSMS_2822 and HSMS 2852, and the RF-DC conversion efficiencies for the curcuits are compared and analyzed in terms of input power and load resistance. When the input power is -20 to 17dBm, the conversion efficiency for HSMS_2852 is larger than in case of HSMS_2822. The output voltage and current at the load of the fabricated rectifying circuit are measured through a dipole antenna when input power is transmitted by a RFID reader and the diatance varies. The measured ouput volatge and current for the distance of 50cm are 2.5V and 5.75mA.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.40-44
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• 2013

The contactless power transfer (CPT) systems have been recently gaining popularity widely since it is an available option to realize the power delivery and storage with connector-free devices across a large air gap. Especially, the CPT with electromagnetic resonance coupling method is possible to exchange energy within 2 m efficiently. However, the power transfer efficiency of CPT in commercialized products has been limited because the impedance matching of coupled coils is sensitive. As a reasonable approach, we combined the CPT system with HTS wire technology and called as, superconducting contactless power transfer (SUCPT) system. Since the superconducting coils have an enough current density, the superconducting antenna and receiver coils at CPT system have a merit to deliver and receive a mass amount of electric energy. In this paper, we present the feasibility of the SUCPT system and examine the transmission properties of SUCPT phenomenon between room temperature and very low temperature at 77 K as long as the receiver is within 1.0 m distance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.65-70
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• 2013

In this paper, we propose a multi-hop cooperative transmission protocol to obtain energy savings in static wireless networks. Each terminal in the network is equipped with a single antenna and each receiver uses equal gain combining technique (EGC) to combine received signals. We also propose a power allocation strategy which optimizes the total transmit power at each stage. Monte-Carlo simulations are presented to evaluate and compare performance of the proposed protocol with the multi-hop direct transmission (MDT) and the cooperative routing protocol proposed by Khadani [8], in terms of the average total transmit power and the average number of required stages.

• Journal of electromagnetic engineering and science
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• v.11 no.3
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• pp.143-151
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• 2011

This paper presents a survey of recent wireless power transfer systems. The issue of wireless power transfer is to achieve a highly efficient system with small positioning errors of the facilities setting. Several theories have been presented to obtain precise system design. This paper presents a summary of design theory for short range power transfer systems and detailed formulations based on a circuit model and an array of infinitesimal dipoles. In addition to these theories, this paper introduces a coil array scheme for improving the efficiency for off axis coils. In the microwave range, tightly coupled resonators provide a highly efficient power transfer system. This paper present san-overlay resonator array consisting of half wavelength microstrip line resonators on the substrate with electromagnetically coupled parasitic elements placed above the bottom resonators. The tight couplings between the waveguide and the load resonator give strong power transmission and achieve a highly efficient system, and enables a contact-less power transfer railroad. Its basic theory and a demonstration of a toy vehicle operating with this system are presented. In the last topic of this paper, harmonic suppression from the rectenna is discussed with respect to acircular microstrip antenna with slits and stubs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.567-572
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• 2015

Discharge characteristics of linear microwave plasma were investigated by using fluid simulation of 2D axis-symmetry based on finite elements method. The microwave power was 2.45 GHz TEM mode and transmitted through linear antenna. Resistive power and pressure were considered simulation variables and argon was used for working gas. A decrease of electron density along the quartz tube was observed in low power condition but relatively uniform plasmas were generated in chamber by increasing the resistive power. The electron temperature was highly detected near the surface of quartz tube because the electron was heated only dielectric surface. The power transmission efficiency decreased and characteristics of surface plasma were observed in high electron density condition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.2
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• pp.151-155
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• 2008

KHST(Korean High Speed Train) has been utilized the total measurement system which evaluates the efficiency and a breakdown of the vehicle and it's results effect to secure reliability of the vehicle. Generally KHST has been received pulse signals from the wheel. It calculates the travel distance after counter the signals to confirm location information of the vehicle. However, there is a limit to measure the location of the vehicle due to slip, slide and the wheel attrition. We have developed a new measurement system by using GPS to complement those errors. In general, GPS receivers are composed of an antenna, tuned to the frequencies transmitted by the satellites, receiver-processors, and a highly-stable clock The GPS mounted on the roof of TT4 in KHST receives a signal from the RS232 communication port. It is connected to the network system in TT3 after converting with TCPIP communication. It is able to track the position of vehicle and synchronize the signal from different measurement system simultaneously. Therefore it is able to chase the fault occurrence, track inspection and electrical interruption at real-time situation more accurately. There is not an error coursed by vehicle conditions such as slip and the slide.