• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.3
• /
• pp.314-319
• /
• 2012

In this paper, a repeater antenna operating at MICS and ISM bands is proposed and the antenna performance including the human body effect is investigated. The proposed antenna is composed of a ZOR(Zeroth Order Resonator) and a loop antenna. A loop antenna is operated at ISM band and a loop antenna capacitively coupled with a ZOR acts as an antenna for MICS band. Simulation was carried out in order to analyze the effects of human body on antenna performance when a human body is located in the near field of an antenna. According to the simulated and measured results, the proposed antenna has -10 dB $S_{11}$ bandwidth wide enough to cover both MICS and ISM bands. The measured peak gains are -28.53 dBi and 3.85 dBi at MICS and ISM band, respectively. The dual band and radiation properties of the proposed antenna are well suited for the WBAN repeater system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.2 s.105
• /
• pp.152-157
• /
• 2006

In this paper, we have analyzed the effects of interference from HAPS ground stations to P-MP FWA base station and to P-MP FWA terminal station using more detail parameters such as a new interference model, a realistic HAPS scenario, practical antenna patterns for both the HAPS system and FWA systems. The analysis results show that, in the case of interference from HAPS GSs into a P-MP BS, compatibility of the two systems can be obtained by using a sectored BS antenna with the boresight directed away from the nadir. However, in the case of interference from HAPS GSs into a P-MP TS, the two systems cannot operate effectively in the same band unless the separation distance is guranteed and/or some form of interference mitigation technique is employed such as dynamic channel allocation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.2 s.105
• /
• pp.110-116
• /
• 2006

In this paper the algorithm of a methodology for the calculation of spectrum requirements was implemented. As well, the influence of traffic distribution ratio among radio access technology groups, spectral efficiency, and flexible spectrum usage(FSU) margin was analyzed in terms of the spectrum requirements, with a view toward for future development of IMT-2000 and systems beyond IMT-2000. The ratio of the spectrum requirement to the traffic distribution ratio is approximately $1\;GHz/20\;\%$, and the spectrum requirement varies from 5 to 9 GHz. As the FSU margin increases by 1.0 dB, the total spectrum requirement decreases by 0.9 dB. The required spectrum for the market input parameter, ${\rho}=0.5$ is 801.63 MHz, while the required spectrum for ${\rho}=1.0$ is 6295.4 MHz. It can be concluded that the market input parameter is the most effective parameter in the calculation of spectrum requirements.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.8 s.99
• /
• pp.848-854
• /
• 2005

The attenuation due to rain has been recognized as one of the major causes of unavailability of radio communication systems operating above about 10 GHz. To design radio links for telecommunications and to evaluate attenuation due to rainfall, it is important to have a good prediction model for rain attenuation such as a model for drop-size distribution of rainfall(DSD), a theoretical model for specific rain attenuation, and an empirical model fur effective path length through rain. In this paper, the extended generalized gamma distribution for drop-size distribution, based on the measurements in Chnugnam National University, is proposed as a new DSD model, and predicted specific attenuation characteristics using proposed DSD model and rain attenuation values in the 44 GHz satellite path using ITU-R effective path length model, are analysed. The predicted attenuation levels are also compared. It is found that an accurate prediction method for DSD is very important to reduce the prediction error in the local satellite path.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.7 no.5
• /
• pp.408-417
• /
• 1996

In this paper, we quantiatively analyze the broadband CDMA systems with high chip rate, which virually eliminates the multipath fading effects by distinguishing each reflected paths in the process of despreading. We model the broadband multipath propagation channel with random time-variant impulse response as a linear filter of tapped delay line to evaluate the performance of broadband CDMA systems in multipath fading environment. This statistical model, based on extensive experimental data, was established to characterize the urban radio propagation medium in various environments. We perform computer simulation of the transmission and reception of broadband CDMA systems by applying it to abve channel model. From the simulation results, we confirm that the broadband CDMA systems inherenly reduce the effects of multipath fading phenomena which causes to degrade the performance of mobile communication systems, based on the results of eye-diagram and BER curve.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.11
• /
• pp.1090-1099
• /
• 2004

In this paper a novel design of equilateral-triangular microstrip antenna using PIN diode fur switching the resonant frequency is presented and experimentally studied. The proposed antenna has changed the resonant frequency by length of spur-lines on the patch, and PIN diodes are utilized to switch the spur-line on and off. The shape of the spur-line is changed according to the on and off states of PIN diode and the equilateral triangular microstrip antenna has different resonant frequencies in accordance with them. The resonant frequency is 1.22 GHz with off states since the surface currents flow the periphery of T shape spur-lines, while the resonant frequency is 1.82 GHz with on states since the surface currents are little effect with the conventional equilateral triangular microstrip antenna. The radiation pattern of the proposed antenna has a good linear polarization with the cross polarization of -20 dB both with on and off states.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.7
• /
• pp.689-697
• /
• 2007

This thesis suggests ways on how to enhance handset radiation power under head phantom condition. Generally, peak EIRP(Effective Isotropic Radiated Power) is used to measure the radiation performance. TRP is more effective to represent indication of mobile radiation performance in the field than EIRP. In this case, we measure the TRP as an index of radiation power. The factors which effect TRP are antenna length, antenna position, folder angle and ground connection method. More detailed analysis is performed over these items. Significant item is ground connection method between main PCB and folder GND. Using the FPCB we connect main GND to folder GND through the hinge near the antenna. The result is that TRP attenuation is decreased about 5 dB under head phantom condition.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.2
• /
• pp.204-212
• /
• 2015

Harmonic effects in a wideband stepped frequency radar(650 MHz~4.5 GHz) have been analyzed. As a result of numerical analysis and simulation, when the second harmonic exists in each frequency, a time-domain result represents an additional object which does not exist but looks to be located at a distance of twice the original object distance. The second harmonics can be removed effectively by low pass filters because there are no other signals between DC and a fundamental signal. In this paper, the harmonic problem can be solved by removing the second harmonics of 650 MHz to 4.5 GHz wideband fundamental signal with two switches and four low pass filters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.8
• /
• pp.772-780
• /
• 2013

The high-altitude electromagnetic pulse(HEMP) conducted environment and the HEMP radiated environment are established as the consequences of a high-altitude nuclear explosion. The IEC 61000-2-10, the international standard, defines the HEMP conducted environment. The IEC 61000-5-5 defines how protective devices for conducted disturbance proposed for HEMP protection shall be specified. The IEC 61000-4-24 deals with methods for testing protective devices for HEMP conducted disturbance. The IEC 61000-4-24:1997 mainly describes the measurement method of small protective components. However, it does not provide the measurement method for a combination filter of a protective component and a filter which is widely used in recent. It is important to consider the characteristic of the measurement setup parameters like thickness and length of the cable and its height above ground plane etc. in establishing measurement setup because HEMP conducted disturbances include the frequency spectrum below 50 MHz. This paper deals with the optimized measurement method, considering the frequency spectrum of HEMP conducted disturbance, current waveform, and analyzing the effects of cables existing in the measurement setup.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.8
• /
• pp.841-848
• /
• 2013

In order for unlicensed devices to co-exist on the same frequency band, the frequency interference mitigation policy is necessary. Because the effects of frequency interference between unlicensed devices may vary depending on the analysis layer, exact interference analysis must be proceeded before making any related spectrum policy. In this paper, a frequency interference between WLAN and WPAN systems that operate at 2.4 GHz ISM band were analyzed in the physical layer and MAC layer, respectively. From the results, we confirmed that the interference analysis in MAC layer is closer to the measured results. Based on these investigations, we suggest a new co-existence criterion for unlicensed devices in MAC layer.