• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1201-1207
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• 2005

When the isolation between transmitter and receiver in Electronic Warfare equipment is not sufficient, the radiated noise jamming signal from the transmitter feeds back into the receiver and interferes with receiving radar pulse signal. Therefore pulse jamming and noise jamming can't be performed together in the same frequency bands. In this paper, we present a time-sharing TX/RX control technique of the switch matrix which inhibits the transmission of noise jamming signal by using the predicted gate of pulse train and also makes the corresponding channel filter operate to receive the radar pulse signal during the predicted gate pulse. This technique was implemented by EPLD and confirmed by experiment. The proposed technique enables the pulse jamming and the noise jamming to be simultaneously executed in multiple jamming environments.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.911-916
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• 2018

Among the various microwaves, the microwaves that we are using in our life are the things that combined with the information on what we need with various technologies. However, the signals that we do not want to get as an information is just noise. Therefore, we need to collect only the necessary information, and other information needs to be blocked. This technology is called Jamming. In this paper, the Partial-Band Jamming System through the Helical Antenna about target 95.1 and 97.3MHz in 88Mhz to 108MHz of the FM radio frequency band was studied.

• Journal of the Korea Computer Industry Society
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• v.2 no.7
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• pp.895-904
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• 2001

In this study, gain can be high because an active double balance mixer was used. Receiving system II was made with receiving system I of low IIP3, a passive double balance mixer which has low gain and high IIP3, and an intermediate frequency amplifier for enhancing the low gain. The result of simulating receiving parameter is as follows： the total NF of receiving system I was 6.4382dB, gain was 53.5dB, and IIP3 was -6.6352dB m. As for the receiving system II, the total NF was 9.70672dB, gain was 47dB, and IIP3 was 3.66729dB m.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.254-260
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• 1999

Meteor Burst Communication can provide effective and economical means of communication where long distance VHF NLOS data transmission is needed; often ranges more than 1000 km. It has been, however, so far considered unsuitable for short distance application because of phenomenal decrease in burst durations, which leads to decreation of total duty rate of the system. This paper extensively analyzes characteristics of shot distance MB(Meteor Burst) path and shows the low duty rate may be improved by increasing burst rate through adapting antenna beam width to cover entire hot-spot region in the space and, by compensating effective burst length through cutting down man-made noises introduced by antenna. Based on the analysis, we are developed a small-opening-cavity antenna, especially designed for short distance MB path. In operation, the antenna is to be buried under ground surface so as to improve directivity and reduces noise introduction. The antenna exhibits power gain of 3 dB with 90 degree beam width and thus enables to illuminate entire hot-spot regions with the elevation angle of 8-90 degree which is the case of transmission less than 100 km. Directivity horizontal to earth surface is suppressed to minimum which enables to cut man-made noises from near-by sources down to more than 3 dB from the level reported with conventional 4 element Yagi. A series of experiments performed on 100 km MB paths have conformed that, with the antenna installed at receiving site, the burst rate and duration time have been noticed to increase by 10 and 20 percent respectively from the values obtained by conventional 4-element Yagi antenna under same testing condition.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.788-801
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• 1998

Meteor Burst Communication can provide effective and economical means of communication where long distance VHF NLOS data transmission is needed ; often ranges more than 1000 km. It has been, however, so far considered unsuitable for short distance application because of phenomenal decrease in burst durations, which leads to decreation of total duty rate of the system. This paper extensively analyzes characteristics of shot distance MB(Meteor Burst) path and shows the low duty rate may be improved by increasing burst rate through adapting antennal beam width to cover entire hot-spot region in the space and, by compensating effective burst length throughcutting down man-made noises introduced by antennal. Based on the analysis, we are developed a small-opening-cavity antennal, especially designed for short distance MB path. In operation, the antenna is to be buried under ground surface so as to improve directivity and reduces noise introduction. The antennal exhibits power gain of 3 dB with 90 degree beam width and thus enables to illuminate entire hot-spot regions with the elevation angle of 8-90 degree which is the case of transmission less than 100 km. Directivity horizontal to earth surface is suppressed to minimum which enables to cut man-made noises from near-by sources down to more than 3 dB from the level reported with conventional 4 element Yagi. A series of experiments performed on 100km MB paths have conformed that, with the antenna installed at receiving site, the burst rate and duration time have been noticed to increase by 10 and 20 percent respectively from the values obtained by conventional 4-element Yagi antennal under same testing condition.

• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.205-212
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• 1999

When we want to observe and record a patient's EEG in an operating room, the operation of electrosurgical unit(ESU) causes undesirable artifacts with high frequency and high voltage. These artifacts make the amplifiers of the conventional EEG system saturated and prevent the system from measuring the EEG signal. This paper describes a high-performance bipolar EEG amplifier for a CSA (compressed spectral array ) system with reduced ESU artifacts. The designed EEG amplifier uses a balanced filter to reduce the ESU artifacts, and isolates the power supply and the signal source of the preamplifier from the ground to cut off the current from the ESU to the amplifier ground. To cancel the common mode noise in high frequency, a high CMRR(common mode rejection ratio) diffferential amplifier is used. Since the developed bipolar EEG amplifier shows high gain, low noise, high CMRR, high input impedance, and low thermal drift, it is possible to observe and record more clean EEG signals in spite of ESU operation. Therefore the amplifier may be applicable to a high-fidelity CSA system.

• KIPS Transactions on Software and Data Engineering
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• v.4 no.12
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• pp.561-570
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• 2015

With the advance of IT technology, contents from digital multimedia devices and softwares are widely used and distributed. However, novice uses them for illegal purpose and hence there are needs for protecting contents and blocking illegal usage through multimedia forensics. In this paper, we present a forensic technique for identifying digital imaging source using sensor pattern noise. First, the way to acquire the sensor pattern noise which comes from the imperfection of photon detector against light is presented. Then, the way to identify the similarity of digital imaging sources is explained after estimating the sensor pattern noises from the reference images and the unknown image. For the performance analysis of the proposed technique, 10 devices including DSLR camera, compact camera, smartphone and camcorder are tested and quantitatively analyzed. Based on the results, the proposed technique can achieve the 99.6% identification accuracy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.61-68
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• 2015

Noise reduction is necessary to compensate for the degradation of recognition performance by various types of noises. Among many noise reduction techniques using microphone array, generalized sidelobe canceller (GSC) has been widely applied to reduce nonstationary noises. The performance of GSC is directly affected by its adaptation mode controller (AMC). That is, accurate target speech detection is essential to guarantee the sufficient noise reduction in pure noise intervals and the less distortion in target speech intervals. Thus, this paper proposes an improved AMC design technique in which the power ratio of the output of fixed beamforming to that of blocking matrix is calculated frequency bandwise and probabilistically modeled by mixture Gaussians for each class. Experimental results show that the proposed algorithm outperforms conventional AMCs in receiver operating curves (ROC) and output SNRs.

• Journal of the Institute of Convergence Signal Processing
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• v.25 no.2
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• pp.52-57
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• 2024

To measure the vortex structures within the turbulent boundary layer, a hot-wire sensor was mounted on a stepper motor controller and moved to the designated measurement points. Near the surface within the flow field, the velocity is relatively slow, making the measurements highly sensitive to electromagnetic interference (EMI) during signal processing. This EMI primarily originates from the power supplies of computers and other electronic equipment. In our experimental setup, EMI was introduced into BNC cables connected to the hot-wire sensor from the powered stepper motor. When power was supplied to the motor controller to move the hot-wire sensor, EMI appeared on the oscilloscope screen. Consequently, unexpected noise was present in the data measured by the hot-wire sensor. To mitigate this and enhance the signal-to-noise ratio (SNR) during measurements, the connecting cables were shielded, and an old computer without EMI shielding was replaced.

• Journal of the Korea Computer Industry Society
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• v.2 no.11
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• pp.1477-1482
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• 2001

In this paper, we examined receiving parameters of receiver and also analyzed them through simulation based on J-STD-018, which is the minimum specification of PCS mobile station. Receiving system was made a passive double balance mixer which has low gain and high IIP3, and an intermediate frequency amplifier for enhancing the low gain. The result of simulating receiving parameter is as follows: noise figure which is the parameter of specification of the receiving sensitivity is 6.746dB, IIP3 which is the parameter of specification of the intermodulation spurious response attenuation is -11.358dBm.