• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.660-667
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• 1998

In this paper, we used differential amplifiers to reduce crosstalk in a wireless in-house optical interconnection in which two channel beams are overlapped. Experimental results show that environmental optical noise is also reduced using the same principle. This method is realized very easily with differential amplifiers without any optical filters or electrical filters. It is very useful in short distance optical interconnections.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.938-943
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• 2004

In this paper, we propose a T-shaped DGS for CPW and provide the closed-form solutions for power loss rate, and bandwidth of the DGS. The proposed T-shaped DGS structure has a range of capacitance(C) 5.5 times wider than the dumbbell-shaped DGS structure. In addition we also analyze relations between R, L, C values of the DGS equivalent circuit and total loss rate, BW, $\omega_0$ of the DGS.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.6 s.121
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• pp.648-655
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• 2007

In this paper, we introduce a dual coil antenna which is useful for reducing the effects of radio frequency noise in an RFID system. A dual coil antenna is composed of two identical coils that are connected in series. The noise voltages in the two coils almost disappear when they are added because the magnitudes are equal and the polarities are opposite. The noise in an RFID reader with a dual coil antenna was 15 dB lower than that with a single coil antenna.

• Journal of Biomedical Engineering Research
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• v.21 no.5
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• pp.513-517
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• 2000

In this study, we fabricated the advanced telemetry system that transmitting media use radio frequency(RF) for the middle range measurement of the physiological signals and receiving media use optical for electromagnetic interference problem. The telemetry system within a size of 65$\times$125$\times$45mm consists of three parts: a RF transmitter, a optical receiver and a physiological signal processing CMOS one chip. Advantages of proposed telemetry system is wireless middle range(50m) FM transmission, reduce electromagnetic interference to a minimum which enables a comfortable bed-side telemetry system.

• Electronics and Telecommunications Trends
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• v.37 no.3
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• pp.33-40
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• 2022

Communication technologies are evolving to meet the ever-increasing demand for fast transmission speeds and large capacity. However, the introduction of new mobile networks, such as 5G, should be accompanied by changes in corresponding frequency and modulation techniques to enable the commercialization of its services. Hence, investigating the human health effects of electromagnetic exposures used in these new communication systems is crucial. Since in vitro electromagnetic experiments can provide essential information on important mechanisms of exposure effects, this article presents in vitro exposure systems necessary for reliable experiments. Moreover, the fundamental requirements for system implementation and the features of various systems are discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.663-668
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• 2008

Recently, World Radio Conference(WRC)-2007 approved the ultrawide bandwidth of 500 MHz for the use of spaceborne synthetic aperture radar in X-band for the EESS(Earth Exploration Satellite Service) in order to improve the SAR imaging resolution. It is concerned about the interference impact from the spaceborne SAR that may cause to most of ground radars due to the extended ultra wideband. In this paper, in order to predict the interference impact of the ground-based radar from the spaceborne radar, radar interference model is presented using radar characteristic parameters by taking into account the operating environments of the spaceborne and ground based radar in the time, space, and spectrum domains. Using the spaceborne SAR model of TerraSAR-X and ground radar model of meteorological radar recommended by ITU-R, the interference impact was assessed through the computer simulation to see the possible interference impact of the ground based radar operating in the Korean peninsula.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1279-1286
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• 2009

This paper addresses the analysis of the interference produced between the LEO(Low Earth Orbit) satellite constellation and FS(Fixed Service) system operating in the same frequency and area. At first, we calculates the interference of FS system from the LEO satellite constellation depending on the number of LEO satellite antenna beams. Simulation results show that the amount of interference that was calculated from each region. This result can be used to define the carrier level for protecting FS system from total interference by LEO satellite constellation. In the second scenario, we calculates the interference of LEO satellite system earth station by the FS link depending on radius of protection area. The presented results can be used to design FS systems minimizing interference to earth station.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1394-1401
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• 2008

This work investigates the effects of vibration on the passive intermodulation distortion characteristics of base station antennas for 800 MHz CDMA mobile communication systems. In general, base station antennas are located at high positions such as on building rooftops or iron towers. Thus the antennas are always affected by random vibrations, coming from various natural environmental factors such as rain and wind, or from living environmental factors such as vehicles and trains passing by. The measured intermodulation distortion characteristics before and after vibration accelerated degradation test show that vibrations are indeed the main cause for the intermodulation distortion performances of such antennas. To minimize the effects of vibrations, a new antenna design isptoposed that has an improved tolerance for vibrations. Experimental results show that the proposed antenna design dramatically reduces the degradation of the intermodulation distortion more than 35 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.183-188
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• 2014

In this paper, the propagation effect of power supply uncertainty on the output of class-F power amplifier has been estimated. Also, a 1.9 GHz, 10 watt class-F power amplifier was measured to verify the estimation and to find the optimal biasing point. By approximating the propagation theory of uncertainties, the propagation effect of bias uncertainty was mathmatically calculated. As a result, the DC biases have propagated uncertainties of 15~70 mW. However, at the optimized bias point, the uncertainty in the output power could be dropped less than 15 mW while the output power has dropped by 0.37 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.299-311
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• 2011

In this paper, we have identified the system instability factors in a bistatic radar system using pulse chasing and considered their effects on the bistatic receiver's MTI(Moving Target Indication) improvement performance. The pulse chasing is a scan method that searchs a restricted area on the transmit pulse-to-pulse basis and the MTI filter is a signal processing that separates a target from some kinds of interferences such as clutter using small number of transmit pulses. Ideal MTI processing performance, e.g., clutter attenuation and improvement, has been limited by the property of the clutter itself, however, the MTI performance in a proposed bistatic receiver configuration could be affected by the receiving beam pointing error during pulse chasing scanning. Also, for the bistatic receiver, we have defined other system instability factors, which result from the time synchronization error, COHO's phase error, the frequency/phase synchronization error, and have analyzed their effects on the system performance improvement.