• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.6
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• pp.498-506
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• 2019

In this paper, we propose a PRF design method to improve the performance of the ESA radar, by excluding the interference from an improper PRF. Like the conventional method, the proposed method also considers the interference between the transmitted signal and the nadir signal, but additionally analyzes the relationship between the interference and the signal beamwidth. The simulation results show that the proposed method quantitatively and qualitatively excluded interference from the PRF and additionally dealt with the beamwidth broadening effect of an ESA radar.

• Composites Research
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• v.33 no.4
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• pp.191-197
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• 2020

In this study, a hybrid metals such as copper (Cu) and nickel (Ni) coated carbon fibers (Ni-Cu/CFs) was prepared by wet laid method to develop a randomly oriented sheet material for high-efficiency electromagnetic interference shielding with the enhanced durability. The prepared sheet materials show a high electromagnetic interference shielding efficiency of 69.4 to 93.0 dB. In addition, the hybrid metals coated Ni-Cu/CFs sheets showed very high durability with harsh chemical/thermal environments due to the effective corrosive and mechanical resistances of Ni surface. In this context, the Ni-Cu/CF sheet possesses longer service life than the Cu/CF sheet, that is, 1.7 times longer.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.883-889
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• 2009

Since the SRRs(Short Range Radar) load on the GVESs(Ground Vehicle Equipment System) are operated within several hundred meters, it is important to suppress the interferences between the SRRs. These interference are reduced using the frequency separation between channels, however this method isn't a perfect solution owing to a difficulty of a realization for the interference suppression. Thus, a pulse-to-pulse coding used to suppress the interference fundamentally is proposed in this paper. The concept, the application method and the test results of the proposed method have been described in this paper.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1194-1199
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• 2010

In this paper, for a relay-based cellular network, a interference avoidance beamforming technique is proposed to enhance direct link capacity while minimizing loss in the capacity of concurrent relaying link. A direct link is transmitted by beamforming at the transmitter, and the relaying link with the least interference to the direct link is scheduled to transmit data by a collision avoidance scheduling algorithm. Simulation results show that the proposed IA beamforming provides a considerable direct link capacity enhancement while minimizing relaying link capacity loss by effectively mitigating inference between concurrent direct and relaying links only with limited feedback.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.427-432
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• 2010

To reduce the outage probability and to increase the transmission capacity, the importance of repeaters in cellular systems is increasing. But a RF(Radio Frequency) repeater has a problem that the output of the transmit antenna is partially feedback to the receive antenna, which is feedback interference. In this paper, we proposed adaptive Sign-Sign LMS(Least Mean Square) algorithm using correlations for the performance enhancement of RF repeater. The weight vector is updated by using sign of input signal and error signal to the least squared error of the conventional algorithms. When compared with the conventional method, the proposed canceller achieves the maximum 10 dB performance gain in terms of the MSE(Mean Square Error).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.2
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• pp.196-208
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• 2002

Since radio interference has occurred in the TRS frequency band in the south coastal area, Korea from 1994, similar interference has been observed in the mobile-cellular frequency band. Measurement showed that the sources of the radio interference are those from the base stations for digital cellular systems in Japan. This because the receiving frequency of the base stations in Korea is same as the transmitting frequency of the base stations in Japan. Since the distance between Korea and Japan is 240 ~ 300 km, we can conclude that the main reason of the interference is ducting. In this paper a ducting channel is modeled by split-step DMFT algorithm, and simulation results for measured index profile far east coast and west sea area are analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.677-687
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• 2008

CR technology is an intelligent technology which can sense the spectrum environment an adaptively adjust the parameters for wireless transmission. In this paper, by using CR-UWB, the spectrum efficiency of the transmission channel is largely improved; Furthermore, the interference to other system can be effectively avoided. In this paper, we propose a solution on interference problem of UWB system using cognitive radio. We use interference temperature model of cognitive radio that has proposed by FCC for estimating interference signal. Calculating channel capacity of UWB system with interference temperature, we suggest how to solve interference problem. We have used genetic algorithm in cognitive engine's calculation precess. The proposed UWB System with cognitive radio shows very efficient in solving interference problem.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.416-425
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• 2002

In this Paper, It is analysed 5 GHz frequency characteristics that carry out interference experimental under the indoor environments for understanding propagation interference between existing 5 GHz band wireless communication system and 5 GHz band wireless LAN system. The interference signal which was generated by signal generator injected to 5 GHz Wireless LAN communication system measured interference characteristics and This radio propagation main interference factors were classified received power level separation by interference source frequency and interference source frequency pulse period & width separation. It is measured transmission rate according to variable data and packet size for conforming the quality of 5 GHz band wireless LAN system. We measured the packet data loss rate and power level of received signal and analyzed its frequency characteristics effected by interference signal.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.434-441
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• 2014

Recently, a mutual interference threat has been increasing among the radar systems due to the rapid growth of the military radar operation. In this paper, the radar interference protection criteria is presented for interoperability in terms of the radar coverage and target detection probability in association with the international recommendation on the interference spectrum by ITU-R. The required criteria for the minimum allowable interference is also presented in terms of INR. In order to ensure the maximum detection probability of the radar under the mutual interference situation, only 5 % of detection range loss is allowed for the case of INR of -6 dB, and required SNR is presented at each INR in terms of the detection range and detection probability. This result will be useful for establishing the interference protection criteria in the combined military radar systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.1030-1035
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• 2003

In this paper, we compare the performance of IS-OFDM(interference suppressing orthogonal frequency division multiplexing) system with that of the conventional OFDM system. Each parallel branch symbol of IS-OFDM is multiplied by the orthogonal sequence and distributed into all sub-carriers. Then, each sub-carrier transmits information composed of the symbol components of all parallel branches in the given frame. The structure of IS-OFDM shows the frequency diversity characteristic. Therefore, IS-OFDM can be robust to the narrowband interference. BER performances are found in the narrow-band interference and a harmonic noise channels. When JSR(Jamming to signal ratio) increases from -10 dB to +10 dB in the constant interference bandwidth, IS-OFDM outperforms the conventional OFDM and the BER difference between IS-OFDM and OFDM is reduced as JSR increases. Also, the similar properly can be shown when interference bandwidth increases at the constant JSR. In the harmonic noise channel, we can find the good performance of IS-OFDM when the h-rate(harmonic noise bandwidth to signal bandwidth ratio) increases from 0.01 to 0.8. So, simulation results show that the IS-OFDM is more robust to the interference than the conventional OFDM.