• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.49-53
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• 2016

Recently, the use of signal compression methods to improve the efficiency of wireless networks have increased. In particular, the MPC system was used in the pitch extraction method and the excitation source of voiced and unvoiced to reduce the bit rate. In general, the MPC system using an excitation source of voiced and unvoiced would result in a distortion of the synthesis speech waveform in the case of voiced and unvoiced consonants in a frame. This is caused by normalization of the synthesis speech waveform in the process of restoring the multi-pulses of the representation segment. This paper presents an ACFBD-MPC (Amplitude Compensation Frequency Band Division-Multi Pulse Coding) using amplitude compensation in a multi-pulses each pitch interval and specific frequency to reduce the distortion of the synthesis speech waveform. The experiments were performed with 16 sentences of male and female voices. The voice signal was A/D converted to 10kHz 12bit. In addition, the ACFBD-MPC system was realized and the SNR of the ACFBD-MPC estimated in the coding condition of 8kbps. As a result, the SNR of ACFBD-MPC was 13.6dB for the female voice and 14.2dB for the male voice. The ACFBD-MPC improved the male and female voice by 1 dB and 0.9 dB, respectively, compared to the traditional MPC. This method is expected to be used for cellular telephones and smartphones using the excitation source with a low bit rate.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.2
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• pp.137-143
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• 2015

This paper presents the intra capacitance modeling based on the winding method and section bobbin for CM choke capable of EMI attenuation of broad bands from lower to higher frequency bands and high frequency type common-mode choke capable of EMI attenuation of high frequency band used in the EMI Block of LED-TV SMPS. The case of high frequency type CM choke can be explained by the parasitic capacitance of three types of CM choke. The winding method of section bobbin type is smaller than the others. The first resonant frequency of the proposed CM choke tends to increase as the parasitic capacitance becomes small and its impedance characteristics improved performance as the first resonant frequency increases. The CM chokes of the proposed section bobbin type shows that in the future, the method may have practical use in LED/LCD-TV SMPS and in several applications, such as LED lighting, adapters, and so on.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.5
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• pp.582-589
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• 2016

Multi-mode monopulse system is widely used for satellite terminal like UAV because of high tracking accuracy and low size/weight profile. In order to calculate tracking error, Multi-mode monopulse system utilizes high-order mode signal, and it should have enough C/N(carrier to noise) level therefore tracking system needs narrow band filtering of received satellite beacon signal as much as possible. However, UAV suffers for beacon frequency drift derived from Doppler effect due to satellite figure 8 movement and UAV maneuvering. Therefore wideband signal processing needs to be considered in advance for exact doppler compensation and consequent time delay. In this paper, we propose the multi-stage Digital Signal processing system for beacon signal, which could minimize the signal delay under high Doppler and low C/N condition.

• Smart Structures and Systems
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• v.23 no.6
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• pp.579-587
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• 2019

In this paper, pounding tuned mass dampers (PTMDs) were designed to mitigate the multi-mode vortex-induced vibration (VIV) of stay cable utilizing the viscous-elastic material's energy-dissipated ability. The PTMD device consists of a cantilever metal rod beam, a metal mass block and a specially designed damping element covered with viscous-elastic material layer. Wind-tunnel experiment on VIV of stay cable model was set up to validate the effectiveness of the PTMD on multi-mode VIV mitigation of stay cable. By analyzing and comparing testing results of all testing cases, it could be verified that the PTMD with viscous-elastic pounding boundary can obviously mitigate the VIV amplitude of the stay cable. Moreover, the installed location and the design parameters of the PTMD device based on the controlled modes of the primary stay cable, would have a certain extent suppression on the other modal vibration of the stay cable, which means that the designed PTMDs are effective among a large band of frequency for the multi-mode VIV control of the stay cable.

• The Journal of the Korea Contents Association
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• v.4 no.1
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• pp.18-23
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• 2004

In this paper, we propose a new visual feature extraction method for content-based image retrieval(CBIR) based on wavelet transform which has both spatial-frequency characteristic and multi-resolution characteristic. We extract visual features for each frequency band in wavelet transformation and use them to CBIR. The lowest frequency band involves spacial information of original image. We extract L feature vectors using fuzzy homogeneity in the wavelet domain, which consider both the wavelet coefficients and the spacial information of each coefficient. Also, we extract 3 feature vectors wing the energy values of high frequency bands, and store those to image database. As a query, we retrieve the most similar image from image database according to the 10 largest homograms(normalized fuzzy homogeneity vectors) and 3 energy values. Simulation results show that the proposed method has good accuracy in image retrieval using 90 texture images.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.234-239
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• 2012

Next generation mobile communication systems have been studied and applied to support various services. In next generation mobile communication systems, the most interested research is the integration of various communication systems and the offer of various services by using high-speed data transmission. The integration of communication systems has been researched by using multi standard modem, while the high-speed data transmission for the offer of various services has been applied by using OFDM. This paper has proposed the method to reduce PAPR by using multi standard modem. with EVM, this paper has also suggested the method to compensate in-band distortion while reducing PAPR. By using the proposed methods, this paper has analyzed and simulated the decrease efficiency of PAPR, the performance of CCDF, and the performance of BER in next generation mobile communication systems. The simulation results improved the performance of next generation mobile communication system can be seen that.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1179-1185
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• 2005

In this paper, novel internal antenna with its controllable resonant frequency is presented for triple-band or over mobile handsets. The operating range can include GSM(880${\~}$960 MHz), GPS(1,575$\pm$10 MHz), DCS(1,710${\~}$1,880 MHz), US-PCS(1,850${\~}$l,990 MHz), and W-CDMA(1,920${\~}$2,170 MHz). The proposed antenna is realized by combination of a half wavelength loaded line and a shorted monopole. A single shorting and feeding points are used and they are common to both antenna structures. By controlling a value of lumped inductance element between shorting point and ground plane, the antenna provides enough bandwidth to cover DCS, US-PCS, and W-CDMA respectively. When these higher bands are controlled by the values of inductance, resonant characteristics in GSM and GPS bands are maintained. In this work, maximum value of the inductor is limited within 3.3 nH to mitigate gain degradation from frequency tuning. As a result, measured maximum gain of antenna is -0.58${\~}$-0.30 dBi in the GSM band, -0.57${\~}$0.43 dBi in the GPS band and 0.38${\~}$1.15 dBi in the DCS/US-PCS/W-CDMA band. In higher band, the proposed antenna is certified that resonant frequency of about 240 MHz can be effectively controlled within gain variation of about 0.77 dB by simulation and measurement.

• Journal of the Korea Society of Computer and Information
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• v.15 no.8
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• pp.59-66
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• 2010

In this paper, the internal antenna for mobile communication handset which is able to control both coupling coefficient and resonant frequency without any major modification of radiator and ground plane of antenna. Novel internal antenna with its controllable resonant frequency is presented for triple-band or over mobile handsets. The operating range can include GSM(880~960 MHz), GPS($1,575{\pm}10MHz$), DCS(1,710~1,880MHz), US-PCS(1,850~1,990 MHz), and W-CDMA(1,920~2,170 MHz). The proposed antenna is realized by combination of a half wavelength loaded line antenna and PIFA(Planner Inverted F Antenna). A single shorting and feeding points are used and they are common to both antenna structures. One of two inductors which is placed at each shorting post, one inductor is for adjusts amount of coupling, and the other controlling the resonant frequency in DCS/US-PCS/WCDMA bands. The inductance range for control of input impedance is between 0nH and 6.8nH, and each of gain variation in GSM, GPS and DCS/US-PCS/WCDMA band is under 0.15dBi, 0.73dBi and 0.29dBi. The inductance range for control of the resonant frequency is between 1640MHz and 2500MHz, and each of gain variation in GSM, GPS and DCS/US-PCS/WCDMA band is under 0.46dBi, 0.53dBi and 0.8dBi.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.10 s.352
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• pp.111-117
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• 2006

Reconfigurable CMOS low-noise amplifier (LAN) has been developed for multi-mode/multi-band wireless receiver. By employing common-gate input stage, the performance can be optimized for multiple operation bands by simply controlling the output load impedance. Although the conventional common-gate LAN has larger than 3dB noise figure (NF), the newly developed negative feedback scheme enables the common-gate input LNA to have less than 2dB NF. To have optimum linearity performance of wireless receiver, the gain of the LNA can be controlled. The LNA implemented in a 0.13mm CMOS technology shows $19{\sim}20dB$ voltage gain, $1.7{\sim}2.0dB$ NF, -2dBm iIP3 at $1.8{\sim}2.5GHz$ frequency range. The LNA dissipates 7mW from a 1.2V supply voltage.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.1
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• pp.75-86
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• 2012

Synthetic Aperture Radar(SAR) imaging system is independent of solar illumination and weather conditions; however, SAR image is difficult to interpret as compared with optical images. It has been increased interest in multi-sensor fusion technique which can improve the interpretability of $SAR^{\circ\circ}$ images by fusing the spectral information from multispectral(MS) image. In this paper, a multi-sensor fusion method based on high-frequency extraction process using Fast Fourier Transform(FFT) and outlier elimination process is proposed, which maintain the spectral content of the original MS image while retaining the spatial detail of the high-resolution SAR image. We used TerraSAR-X which is constructed on the same X-band SAR system as KOMPSAT-5 and KOMPSAT-2 MS image as the test data set to evaluate the proposed method. In order to evaluate the efficiency of the proposed method, the fusion result was compared visually and quantitatively with the result obtained using existing fusion algorithms. The evaluation results showed that the proposed image fusion method achieved successful results in the fusion of SAR and MS image compared with the existing fusion algorithms.