• Journal of Broadcast Engineering
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• v.12 no.6
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• pp.641-648
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• 2007

The decoding structure of up-to-date ATSC DTV receivers is well optimized, and it seems that 14.6 dB is the unbreakable minimum SNR in the AWGN channel. But the SNR satisfying the Shannon capacity of DTV receivers is 11.76 dB, So, the SNR gab between the 14.6 dB and the 11.76 dB is about 2.8 dB. In order to approach the Shannon capacity we propose a recursive trellis decoder which uses reliable feedback data obtained by an RS decoder. The performance enhancement of about 0.8 dB can be achieved in case of the AWGN channel.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.219-226
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• 2000

In this paper, we design and implement a IF(intermediate frequency) module for WLL(wireless local loop) CDMA(code division multiple access) basestation. The implemented IF transceiver is consists of transmitter, receiver and local oscillator. The considered signal bandwidth is 10 MHz and the local carrier frequency is 40 MHz. As test results, the If transmitter output power is -5dBm $\pm3dB$when the baseband input is -10dBm $\pm3dB$, and the IF receiver output power is -10dBm $\pm3dB$when the IF input is -5dBm $\pm3dB$. Also the AGC(automatic gain control) circuit has dynamic range of 9 dB from -7dBm to +2dBm with output power 2dBm. And the group delay characteristic is analyzed by comparing the phase delay from 1 MHz to 5 MHz and the phase distortion is very low. We can conclude that this IF system can be applied to high speed data rate communication system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.196-199
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• 2000

In this paper, we have designed a low-noise amplifier for the down-converter to apply the K-band Mu-kung-hwa satellite downconvertion. We have designed on three-stage to satisfy the property of low-noise amplifier for the down-converter required at least 30dB gain. The simulaition results for the designed three-stage Low-noise amplifier are measured that 33dB, gain and 0.93dB, noise-figure From 19.200 to 20.200, and The experiment results of the fabric are measured that 25dB, gain and 1.5dB, noise-figure. Since Input reflection coefficient and otput resection coefficient are -25dB and -28dB, respectively, and VSWR is lower than 1.5, this amplifier can be used as a low-noise amplifier for the down-converter to apply the K-band Mu-kung-hwa satellite downconvertion.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1106-1113
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• 2005

This paper presents a dual-band mixer for multi-standards of IEEE 802.1la/b/g using a single local oscillator, so as to improve the defects of legacy systems. Those systems have duplicate local oscillators and mixers to handle dual band signals, increasing complexity of system and power loss. The proposed circuit shows 11.6 dB, 16.8 dB of conversion loss and 8.77 dBm, 12.5 dBm of IIP3(Input 3rd Intercept Point) for respective bands when the two RF inputs of 2.452 and 5.260 GHz are down-converted to the identical 356 MHz If frequency. The RF-LO isolations are measured 36 dB, 41 dB at each frequencies and over 50 dB of LO-IF isolations are achieved at all cases.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.581-584
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• 2000

In order to obtain the fundamental data about method of luring fish schools by underwater audible sound, the auditory threshold of black rockfish Sebastes inermis on the coast of Cheju Island was investigated by heartbeat conditioning technique using pure tones coupled with a delayed electric shock, The audible range of black rockfish extended from 80 Hz to 800 Hz with a peak sensitivity at 300 Hz. The mean auditory thresholds of black rockfish at the frequencies of 80 Hz, 100 Hz, 200 Hz, 300 Hz, 500 Hz and 800 Hz were 102 dB, 103 dB, 99 dB, 96 dB, 116 dB and 122 dB, respectively, As the frequency became higher than 300 Hz, the auditory threshold increased rapidly.

• Journal of Elementary Mathematics Education in Korea
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• v.23 no.3
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• pp.273-288
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• 2019

This study focuses on understanding proportionality, in particular, what constitutes relational understanding of a:b=c:d, which is called proportional expression. The meanings of a:b=c:d are analyzed and some suggestions are offered for improving the teaching and learning of it. The equation a:b=c:d has three different meanings. First, it represents two different structures in one proportional situation. Second, it represents a common structure in two different proportional situations. Finally, it represents a number or a quantity underlying in different proportional situations. It is important to choose and use a unit flexibly to understand the first and the second meanings of a:b=c:d, Double strip diagram and double number line are useful to visualize the meanings of a:b=c:d. In addition, what a number or a quantity in the third meaning of a:b=c:d refers to in proportional situations should be emphasized in teaching and learning of a:b=c:d.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1687-1693
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• 2015

Recently, demand for digital image processing devices increases rapidly, more clear images have been required. But, in the process of digital image acquisition, processing and transmission, image degradation occurs due to various external reasons and researches about noise reduction are on the rise. Therefore, this study suggested the algorithm to process AWGN(additive white Gaussian noise) by separately processing as three levels according to the pixel distribution in the mask in order to remove AWGN(additive white Gaussian noise) which is added in the image. Regarding the processed results by applying Barbara images which were damaged by AWGN(σ = 15), suggested algorithm showed the improvement by 2.87[dB], 2.95[dB], 2.88[dB], 1.52[dB], 1.49[dB], 1.58[dB] and 1.25[dB] respectively compared with the existing MF(5 × 5), A-TMF(5 × 5), AWMF(5 × 5), MF(3 × 3), A-TMF(3 × 3), AWMF(3 × 3), GF(5 × 5).

• Journal of Fisheries and Marine Sciences Education
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• v.12 no.1
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• pp.1-10
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• 2000

In order to obtain the fundamental data on the auditory thresholds of fishes for marine ranching, the auditory thresholds of black rock fish Sebastes Schlegeli were measured in the presence of masking noise in the spectrum level range of 73 - 83dB (0dB re $1{\mu}Pa/{\sqrt{Hz}}$) with a classical cardiac conditioning technique. Critical ratios were about 19 - 30dB at 80 - 300Hz and 46 - 54dB at 500 - 800Hz. The ratio increased almost linearly with increasing frequency to 500Hz. The noise spectrum level at the start of masking was about 70dB within the frequency range of 80 - 800Hz excepting 65dB at 300Hz. This suggests that hearing of the black rock fish is masked in the natural environment with the noise spectrum level above 65dB. The sound pressure level of which the signal sound of 100 - 200Hz is recognized by black rock fish under the ambient noise is above 90dB and the critical ratio of them is above 20dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.6 s.121
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• pp.629-638
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• 2007

The methods of bandwidth measurement in the field environments are notified in ITU-R spectrum monitoring(SM) documents. But, these methods for terrestrial DTV and T-DMB are not informed yet. The x-dB bandwidth is the most suitable method fer the bandwidth measurement of terrestrial digital broadcasting signals. So, we proposed the suitable x-dB value for x-dB bandwidth measurement of the digital broadcasting signal that is not notified in ITU-R SM documents. As a result, we derived the x dB value of -12 dB and -8 dB that can be used fer estimation of occupied bandwidth of DTV and T-DMB signals respectively by x dB bandwidth measurement in field environments.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.209-212
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• 1997

Spectral gain variation characteristics of the silica-based erbium doped fiber amplifiers is investigated in the 1545-1557 nm wavelength region. For a given length of the erbium doped fiber, the gain($G_0$) with minimum spectral gain variation is uniquely determined. The spectral gain imbalance DG is nearly proportional to the difference between G0 and the operating gain(G) with the proportional constant of 0.1-0.2 dB/dB. For the gain flattened EDFA at the input power of -20 dBm/ch. and the gain of 21 dB, the output power and the optical signal to noise variations after 12 cascaded EDFAs were 5 dB and 3 dB, respectively.