• ETRI Journal
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• v.29 no.2
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• pp.135-142
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• 2007

The small anechoic chambers built by many small-/medium-sized companies and universities present difficulties in testing electrically large antennas because the chamber size cannot satisfy the far-field criterion of large antennas. In this paper, a method for Fresnel-region measurement on a cylindrical surface with variation of the measurement height is proposed and verified by both calculations and experiments. We implement the proposed method using a direct far-field measurement system by adding a few supporting structures. The results show good accuracy.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.11 no.1
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• pp.10-15
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• 2012

Ultra wideband (UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geo-location, and other applications. The energy of UWB signal is extremely spread from near DC (Direct Current) to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional wireless systems sharing the frequency bands such as broadcasting system. This paper experimentally evaluates the interference from two kinds of UWB sources, namely an orthogonal frequency division multiplex UWB source and an impulse radio UWB source, to a broadcasting transmission system. The S/N ratio degradation of broadcasting system is presented. From these experimental results, we show that in all practical cases UWB system can be coexisted 35m distance in-band broadcasting network.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.53-56
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• 2001

In this paper we discuss a direct satellite broadcasting system for vehicle. The proposed satellite-steering algorithm and controller based on it are designed for a communication and broadcasting system which uses the Mugungwha satellite. The Mugungwha satellite that the proposed system should steer is a geostationary orbit device. The satellite-steering algorithm computes azimuth and elevation with reference to a stationary point on earth. This is extended to a real satellite steering algorithm that considers position and attitude. Real moving position and attitude are represented by latitude, longitude, roll, pitch and yaw. To apply these five pieces of information to the reference satellite steering algorithm, we introduce Euler's degree coordinates that express independently the rotation of each axis relative to an axis. There are two ways a basic algorithm of the antenna of a vehicle can track and orient to satellite. One way is a feedback loop method for broadcasting gain, while the other is a feedback loop method for position and attitude of a vehicle. In the present paper, we design a controller of satellite broadcasting system for a vehicle using an algorithm that combines the two methods. We performed a simulation and experiment to prove effectiveness.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1996.06a
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• pp.739-744
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• 1996

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.13-19
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• 2014

Improvement of performances of potable communication devices such as laptops, tablets, and smart-phones enables people to do group meetings in any place. However, even though group members in a meeting locate close, data or information to be shared in the group are exchanged through the cellular networks. This increases unnecessary traffic loads in the wireless/backbone networks and as consequence it increase delays in communications. To resolve the problem, an android-based application is developed in this paper. The application utilizes Wi-Fi Direct so that all members in the meeting can direct exchange materials for the meeting without using cellular networks.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.309-313
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• 2009

In this paper, the network performance of a turbo coded optical code division multiple access (CDMA) system with cross-layer, which is between physical and network layers, concept is analyzed and simulated. We consider physical and MAC layers in a cross-layer concept. An intensity-modulated/direct-detection (IM/DD) optical system employing pulse position modulation (PPM) for satellite broadcasting communications is considered. In order to increase the system performance, turbo codes composed of parallel concatenated convolutional codes (PCCCs) is utilized. The network performance is evaluated in terms of bit error probability (BEP). From the simulation results, it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding and decoding complexity. Also, it is confirmed that the performance of such an optical CDMA network can be substantially improved by increasing the interleaver length and the number of iterations in the decoding process. The results of this paper can be applied to implement the satellite broadcasting communications.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.443-447
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• 2005

In this paper, a low noise amplifier(LNA) in a receiver of a Low Noise Block Down Converter (LNB) for direct broadcasting service(DBS) is implemented using GaAs HEMT. The 2-stage LNA is designed for the bandwidth of 11.7GHz - 12.2GHz. The result of a simulation of the LNA using Advanced Design System(ADS) shows that the noise figure is less than 1.4dB, the gain is greater than 23dB and the flatness is 1dB in the bandwidth of 11.7 to 12.2GHz.

• International journal of advanced smart convergence
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• v.4 no.2
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• pp.103-108
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• 2015

The electric utility has the responsibility of reducing the impact of peaks on electricity demand and related costs. Therefore, they have introduced Direct Load Control System (DLCS) to automate the external control of shedding customer load that it controls. Since the number of customer load participating in the DLC program are keep increasing, DLCS operators a re facing difficulty in monitoring and controlling customer load. The existing DLCS needs constant operator intervention, e.g., whenever the load is about to exceed a predefined amount, it needs operator's intervention to control the on/off status of the load. Therefore, DLCS operators need the state-of-the-art DLCS, which can control automatically the on/off status of the customer load without intervention as much as possible. This paper presents an intelligent DLCS using the active database. The proposed DLCS is applying the active database to DLCS which can avoid operator's intervention as much as possible. To demonstrate the validity of the proposed system, variable production rules and intelligent demand controller are presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.9
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• pp.2514-2525
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• 1996

This paper presents the possibility of the satellite broadcasting reception as a means of microstrip antenna of the planar structure. The paper discusses the design of the optimal KOREASAT DBS(Direct Broadcasting Satellite) reception microstrip antenna. Experimental results for ta 16*16 array antenna of size 35*35cm are also described. Itsgain is over 28dB in the frequency range of 11.7~12.0GHz DBS band. The measured NHK broadcasting C/N ratio of 16816 array antenna is over 10dB in Pusan. It is expected that good picture quality of C/N .GEQ. 12dB can be obtained for domestic use if this microstrip antenna is used in KOREASAT broadcasting receiving system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.839-847
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• 1999

This paper presents the performance evaluation of direct broadcasting satellite by monte-carlo(MC) and quasi-analytic(QA) simulation method in the existence of uplink/downlink adjacent channel interference(ACI), co-channel interference(CCI), and gaussian noise. Korea's satellite system parameters and link design are used at the simulation. MC and QA simulation methods are a valuable adjunct to analytical performance.