• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.898-906
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• 2002

In this paper, we investigated the improvement degree of transmission distance of the various initial frequency chirped optical pulse with 5 dBm initial power dependence on the various bit rate and fiber dispersion coefficient, when MSSI(Mid-Span Spectral Inversion) with the optimal pump power condition is adopted for the compensation method for optical pulse distortion. And we analyzed the influence of mutual relation of optical pulse frequency chirp and Kerr effect on the MSSI methods for the long-haul optical transmission through the computer simulation. We found that the compensation degree of distorted optical pulse varies as a consequence of the variation of combined phase modulation of self phase modulation(Kerr effect) and initial frequency chirp parameter dependence on the fiber dispersion coefficient. And we found that, if the transmission bit rate is increased k times, the dispersion coefficient value of dispersion shift fiber is decreased $2^k$ times so as to be almost the same performance of the transmission system with k times lower bit rate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.858-864
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• 2002

In this paper, Analyzed Performance of TH/UWB(Time Hopping/Ultra Wideband after Impulse Radio) system in interference environment by existing system that use same frequency band. In case interference fraction ratio is below 0.1, consider and analyzed in case influence through interference in IR system that is shared in 3.1 - 10.6 GHz band hereafter as case that use very small and narrow band than IR system such as 80 MHz bandwidth of ISM band or 802.1la's use bandwidth 20 MHz in 5 GHz band. According to result, we could know that Performance change according to possession band width of interference shows greatly than size of interference electric power. Also, interference fraction ratio is big (more than 0.1) narrowband interference in partial band interference environment, could get Performance improvement of big width increasing pulse repetition number. But, could know that do not influence hardly in system performance when interference fraction ratio is small (below 0.1) narrowband interference. Therefore, may receive the best system performance and transfer efficiency by set the most suitable pulse repetition number according to bandwidth fraction ratio of interference through correct interference fraction ratio estimation and apply proper interference suppression techniques.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.6
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• pp.630-637
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• 2003

This paper explains the impact of frequency error on the performance of WCDMA mobile communication systems and what brings about the frequency error between the base station and the mobile station, and then presents automatic frequency error correction method in mobile receiver. On the basis of system requirement related to frequency stability, the integration test between the base station and the mobile station was accomplished. After applying automatic frequency error correction to mobile receiver, 4 Hz of frequency error at transmitting frequency was obtained. The result met frequency error requirement of ${\pm}$0.1 ppm(about ${\pm}$200 ㎐). Performance degradation due to frequency error was measured by means of Error Vector Magnitude(EVM) at transmitter and Ec/Io at receiver, respectively and then the interface requirement between Modem control signal and RF was suggested to improve the correctness of frequency error control.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.978-984
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• 2008

In this paper, we propose a RFID metal tag antenna with a minimum by size of a metal surface to attach. This proposed tag antenna is a patch antenna which is able to stick on metal surface and designed for very slim structure ($119{\times}30{\times}1.6$ mm) antenna that is matched to a chip impedance. This has a loop coupling feeding and consists of a inner radiator and a outer radiator. The outer radiator activates the current to concentrate on the inner radiator regardless of metal size to attach. Also the tag antenna is designed by CST microwave tool and the performance is measured in the anechoic chamber. The optimum antenna has 3.77 % of the matching bandwidth($S_{11}<-10$ dB). The readable range of the tag antenna is about 2.9 m on metal(max. size $700{\times}700$ mm) and 5.5 m in free space according to the measurement results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.67-75
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• 2011

This paper investigates the radiated emission from the enclosure aperture, when the enclosure contains a 4-layer PCB and the PCB is driven by a pulse train additive with the switching noise from an active device. Radiated emission characteristics with and without switch noise cases, respectively, are analyzed by changing the PCB location and the slot direction. The equivalent circuit of a DC-DC converter is used to simulate the switching noise of active device. Also, MWS simulation results are directly connected to the ADS simulator as a 2-port block. The simulated results are compared with the measured ones.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.47-58
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• 2011

MTI filter is used to separate target signal from clutter in many radar signal processing. By suppressing clutter before CFAR detection, the detection performance can be improved. As a radar system designed, a design engineer generally takes averaged SNR and CNR into account and does not include the effect of MTI filter's frequency response. In practice, when the signals including clutter are pass through the filter, SNR is widely varying according to target velocity and CNR is also varying according to clutter center frequency and spectrum spreading. In this paper, we have derived the relationship between the MTI filter's frequency response and a target's velocity and a clutter's spectrum characteristics. With the variation of SNR and CNR at the filter output, the detection performance of CFAR has been analyzed by the simulation and has made certain of their influences on the performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1168-1177
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• 2004

This paper presents the characteristics of the electromagnetically coupled small broadband disk-loaded monopole antenna with multiple shorting pins. The electromagnetically coupled monopole antenna can achieve broad bandwidth by controlling resonant frequency of the rectangular disk-loaded monopole and a probe with the spiral strip line monopole. The number and arrangement of the shorting pin affect the capacitance of the disk. The variation of the capacitance changes resonant frequency of the antenna, and therefore, its electrical sizes and frequency bandwidth are also affected. The antenna with three shorting pins has a volume of $0.094\lambda_0{\times}0.094\lambda_0{\times}0.094\lambda_0$ in electrical length and the frequency bandwidth of $26.8\%\;for\;VSWR\leq2$ with the center frequency at 2.556 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.685-691
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• 2003

This paper newly analyzes the effect of the phase noise in the frequency synthesizer on the performance of SFH/M-NCFSK system by standard frequency deviation(equation omitted) when noncoherent FSK demodulation of the square-law detector is considered. We derive the SER in the SFH system and analyze the effect of phase noise on the SFH/M-NCFSK system performance according to the hopping frequency spacing (1/T$\_$h/) and the variation of the standard frequency deviation (equation omitted). The required SNR is about 13.4 dB to meet Ps=10$\^$-3/ when the standard frequency deviation is about 4.0 Hz and the hopping frequency spacing (1/T$\_$h/) in the SFH/2-NCFSK system is 30. So, there is about 2.4 dB power penalty than the phase noise-free system. If the hopping frequency spacing 1/T$\_$h/ is under 30, the error floor may happen and SER considerably grows up. We show that the analytic results closely match with the simulation results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.152-160
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• 2008

In this paper, we analyze the performance of a direct-conversion UHF RFID reader with the range correlation effects of the phase noise. Since a UHF RFIB system uses the same oscillator to generate the transmitted carrier and the local oscillation, the periodic interference and phase noise reduction effects occur due to time delay between two signals. Through exact theory and simulation, we verify how to cancel the periodic interference phenomena using I/Q diversity combining technique. And, we analyze phase noise reduction effects due to range correlation as a function of the tag-reader distance and the offset frequency Using these results, we simulate the symbol-error-rate performance with respect to phase noise with and without range correation effects. We show that the phase noise of the local oscillator has little effect on the symbol-error-rate performance because of phase noise reduction by range correlation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.8
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• pp.665-675
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• 2016

With the development of active phased array radar technology in recent years, active phased array antennas, which digitally combine signals received from subarray units using dozens of digital receiver, have been developed. The beam characteristics are greatly affected by the shape of the subarray structure as well as the weight of subarray in digital beamforming. So in this paper, the method to generate subarray structures by using recursive element exchanging method and the method to optimize subarray structures that can minimize sidelobes of operating beams are proposed. Additionally it presents the result to find the optimized subarray structure to minimize the maximum sidelobe of monopulse beam and pencil multi-beam respectively or simultaneously which are commonly used for digital beamforming by applying the algorithm propsed in this paper.