• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.387-393
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• 1997

In order to apply WO3 thin films to the semiconducting NOx gas sensors as a sensing material, which have been expected to show good electrical properties, such as large sensitivity, rapid responsibility, and high selectivity, the fabrication method and their sensing characteristics were studied. The variations of surface morphologies, crystallographic orientations and crystallinity with the WO3 thin film growing methods thermal evaporation and DC sputtering methods were investigated by using scanning electron microscopy (SEM) and X-ray diffraction(XRD) analysis. As a result of sensitivity (Rgas/Rair) measurements for the 5 ppm NO2 test gas, the sensitivity values were 113 for the sputtered films and 93 for the evaporated films. It was also observed that the recovery rate of a sensing signal after measuring sensitivity was faster in the sputtered films than in the evaporated films.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.1
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• pp.1-13
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• 1995

In this paper, a specification for wireless LAN MODEM using direct sequence spread spectrum (DS/SS) technique is presented. Some algorithms and hardware architectures for an efficient implementation of the DS/SS MODEM are suggested. In the method, all baseband signal processing are done digitally for single chip implementation. Schemes of DQPSK baseband modulation/demodulation, despreading with digital matched filter, digital timing recovery, and efficient carrier sensing are among the discussed algorithms. We also performed various kinds of simulations to evaluate the system performance and to extract parameters for hardware implementation. In addition, the pictorial view of ASIC of the SS MODEM is also shown.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.775-779
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• 1999

This paper presents design of AGC(Automatic Gain Control) and DC offset remover suitable for cable modem which makes use of QAM(Quadrature Amplitude Modulation) scheme. Since QAM has multi-level signal characteristic, for high-order QAM, the constellation is dense and the distance of decision boundary between adjacent symbols is short. So AGC and DC offset remover must be designed optionally for preventing performance degradation. AGC is designed into feedback type and is related to the STR(Symbol Timing Recovery)and Paff interpolation algorithm. Whereas AGC need to perform average power detection during many symbols by comparison with the reference power, DC offset remover uses only the instant polarity decision such that simple implementation can be achieved with good performance. Though the AGC and DC offset remover are simulated here only for 256 QAM scheme for convenience'sake, it can be applied to other multi-level QAM or PSK modulation scheme.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.219-222
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• 2006

In this paper we present a cryptanalysis of the generalized patchwork algorithm under the assumption that the attacker possesses only a single copy of the watermarked audio. In the scheme, watermark is inserted by modifying randomly chosen DCT values in each block of the original audio. Towards the attack we first fit low degree polynomials (which minimize the mean square error) on the data available from each block of the watermarked content. Then we replace the corresponding DCT data of the at-tacked audio by the available data from the polynomials to construct an attacked audio. The technique nullifies the modification achieved during watermark embedding. Experimental results show that recovery of the watermark becomes difficult after the attack.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.170-176
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• 2007

In this paper, we improve performance for system when the carrier recovery signal is not perfect in the multipath mobile wireless communication fast fading channel based on DS-CDMA system. In the case, we use the phase estimation, diversity and adaptive FEC code technique in order to overcome this carrier phase error and mobile wireless fading. As a results in DS-CDMA system, we know that the appropriate use of diversity and adaptive FEC code technique reduced considerably performance degradation due to phase error.

• Journal of Sensor Science and Technology
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• v.18 no.4
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• pp.269-273
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• 2009

In this paper, a study on a portable hydrogen alarm system based on the palladium coated single mode fiber sensor has been reported. The fabricated hydrogen sensor exhibited 0.14 dB, 0.41 dB and 0.54 dB optical intensity variation when it was exposed by the nitrogen and hydrogen mixed gas containing 0.5 %, 1 % and 4 % of the hydrogen concentration, respectively. The fabricated sensor exhibited 20 second of response time and 120 second of recovery time for 4 % hydrogen containing gas. The fiber optics layout and software algorithm for detection of hydrogen leakage have been presented. The implanted portable hydrogen alarm system successfully generated an alarm signal when a 4 % hydrogen containing gas was leaked out.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.252-258
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• 2000

In this paper, we improve error performance for BPSK and QPSK when the carrier recovery signal is not perfect in the multipath Rician fading channel based on DS-CDMA system. In the case, we use the MRC(Maximal Ratio Combining) diversity and convolutional coding technique in order to overcome this carrier phase error and Rician fading. With results of analysis, we know that the appropriate use of MRC diversity and convolutional code reduced considerably performance degradation due to phase error.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.601-603
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• 1998

In this paper, Hadamard transform imaging spectrometers utilizing Grill spectrometers are proposed. General Hadamard Transform Spectrometers (HTS) carry out one-encoding through input masks, but Grill spectrometers carry out double-encoding through entrance and exit masks. Thus Grill spectrometers increase the signal-to-noise ratio by double-encoding. we reconfigure the system by using the Grill spectrometers which use a left cyclic S-matrix instead of the conventional right cyclic one. Then, we model the system and apply the mask characteristics method, i.e. $T^{I}$ method, to complete fast algorithm. Through computer simulations, we want to prove the superiority of the proposed system by comparing with the conventional HTS. From Observations concerning the average mean square error(AMSE) associated with estimates from the $T^{I}$ spectrum-recovery method, the relative performances of the two systems are compared.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.4
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• pp.407-418
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• 2014

As the high-throughput requirement in the next generation communication system increases, it becomes essential to implement high-throughput SISO (Soft-Input Soft-Output) decoder with minimal hardware resources. In this paper, we present the comparison results between cascaded radix-4 ACS (Add-Compare-Select) and LUT (Look-Up Table)-based radix-4 ACS in terms of delay, area, and power consumption. The hardware overhead incurred from the retiming technique used for high speed radix-4 ACS operation is also analyzed. According to the various analysis results, high-throughput radix-4 SISO decoding architecture based on simple path metric recovery circuit is proposed to minimize the hardware resources. The proposed architecture is implemented in 65 nm CMOS process and memory requirement and power consumption can be reduced up to 78% and 32%, respectively, while achieving high-throughput requirement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.978-985
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• 2000

Blind equalizers recover the transmitted data using statistical characteristics of the signal alone. Among many alternatives, steepest gradient descent type algorithms such as the CMA and Sato algorithm are most widely utilized in practice. In this paper we propose a dual-mode NCMA algorithm, which combines the advantages of the dual mode CMA and Normalized CMA (NCMA) with the dual mode phase recovery algorithm. In addition, we perform computer simulations to demonstrate the performance improvement of the proposed algorithm with a QAM system. Simulation results show that the presented algorithm has a faster convergence speed and smaller steady-state residual error than the CMA and dual-mode CMA.