• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.5
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• pp.501-509
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• 2011

Software defined radio(SDR) has a goal that places the analog-to-digital converter(ADC) as near the antenna as possible. But current technique actually can't do analog-to-digital converting about RF band signals. So one method is studying that samples RF band signals to IF band. One of the ways Sub-Sampling technique can convert signals from RF band to IF band without oscillator. If Sub-Sampling technique is used, over 2 bands can convert signals from RF band to IF band. But due to the filter performance in RF band, it is possible to generate interference between signals that is converted in low frequency band. The effect degrades performance. In this paper, we propose one method that uses time division multiplexing(TDM) method as a solution to avoid interference between signals. By doing TDM and Sub-Sampling at the same time that method can get signals without large changes of structures.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.821-824
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• 1999

In distributed arithmetic-based architecture for an inner product between two length-N vectors, the size of the ROM increases exponentially with N. Moreover, the ROMs are generally the bottleneck of speed, especially when their sire is large. In this paper, a ROM size reduction technique for DA (Distributed Arithmetic) is proposed. The proposed method is based on modified OBC (Offset Binary Coding) and control circuit reduction technique. By simulations, it is shown that the use of the proposed technique can result in reduction in the number of gates up to 50%.

• Journal of Korean Society of Forest Science
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• v.111 no.1
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• pp.165-176
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• 2022

To raise awareness of carbon reduction in climate change, the Korea Forest Service has developed and adopted a forest carbon offset program, which aims to reduce carbon levels based on forest management. However, to maintain the forest carbon offset program, challenges such as the lack of a forest monitoring system to manage and maintain the program, must be faced. In this context, we investigated the limitations of conducting forest carbon offset programs using a number of interview techniques, including in-depth interview and questionnaire survey methods. The questionnaire surveys were developed based on the results of a literature review along with a preinterview and in-depth survey of the people in charge of the forest carbon offset program. The Irving Seidman technique was adopted for the in-depth interviews. Additionally, descriptive and frequency analyses were conducted to identify the characteristics of perception. Lastly, logistic regression was used to identify the limiting factors that affect the willingness to perform forest carbon offset monitoring activity. Results showed that the project managers or people in charge of the forest carbon offset program lacked expertise in forest carbon offset programs, which negatively affected their willingness to perform monitoring activity. Additionally, the study revealed a number of limiting factors that hindered the monitoring of forest carbon offset projects. Improving understanding using the approaches presented in this study may contribute to increasing the benefits associated with the forest carbon offset program in South Korea.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.723-730
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• 2007

This paper shows how the ACLR of power amplifier can be reduced by using Anti-phase IMD linearization technique which generate anti-phase IMD in the driver stage compare to output stage's IMD. And design process proposed. From the experimental result of W-CDMA 4FA input signal, this amplifier has ACLR -55 dBc@5 MHz offset at 30 watts average power. Compare to optimum matching technique to get maximum power gain, this technique has been improved ACLR by 12 dBc. Also this amplifier meets 50 watts average output power amplifier specification in domestic market.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.2
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• pp.62-69
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• 2008

This paper proposes linearization technique that the linearity is improved by controlling IMD between the drive stage and the output stage. From the experimental results of W-CDMA 4FA input signal, this amplifier has ACLR of -48dBc@5MHz offset at 50W average power. Proposed linearization technique provides predistortion effect for using drive amplifier without additional circuit, which is the significant in this paper that it makes up for the weak point of analog predistortion method and feedforward method.

• Korean Journal of Remote Sensing
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• v.37 no.6_3
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• pp.2035-2046
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• 2021

Glacier movement speed is the most basic measurement for glacial dynamics research and is a very important indicator in predicting sea level rise due to climate change. In this study, the two-dimensional velocity measurements of Campbell Glacier located in Terra Nova Bay in East Antarctica were observed through the SAR offset tracking technique. For this purpose, domestic KOMPSAT-5 SAR satellite images taken on July 9, 2021 and August 6, 2021 were acquired. The Multi-kernel SAR offset tracking proposed through previous studies is a technique to obtain the optimal result that satisfies both resolution and precision. However, since offset tracking is repeatedly performed according to the size of the kernel, intensive computational power and time are required. Therefore, in this study, we strategically proposed a coarse-to-fine offset tracking approach. Through coarse-to-fine SAR offset tracking, it is possible to obtain a result with improved observation precision (especially, about 4 times in azimuth direction) while maintaining resolution compared to general offset tracking results. Using this proposed technique, a two-dimensional velocity measurements of Campbell Glacier were generated. As a result of analyzing the two-dimensional movement velocity image, it was observed that the grounding line of Campbell Glacier exists at approximately latitude -74.56N. The flow velocity of Campbell Glacier Tongue analyzed in this study (185-237 m/yr) increased compared to that of 1988-1989 (140-240 m/yr). And compared to the flow velocity (181-268 m/yr) in 2010-2012, the movement speed near the ground line was similar, but it was confirmed that the movement speed at the end of the Campbell Glacier Tongue decreased. However, there is a possibility that this is an error that occurs because the study result of this study is an annual rate of glacier movement that occurred for 28 days. For accurate comparison, it will be necessary to expand the data in time series and accurately calculate the annual rate. Through this study, the two-dimensional velocity measurements of the glacier were observed for the first time using the KOMPSAT-5 satellite image, a domestic X-band SAR satellite. It was confirmed that the coarse-to-fine SAR offset tracking approach of the KOMPSAT-5 SAR image is very useful for observing the two-dimensional velocity of glacier movements.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.1
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• pp.185-194
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• 2023

The 4-axis strain-gauge, which is widely applied to military weapon systems, is operated in poor temperature and vibration conditions, tolerance may increase and malfunctions may occur. To improve this, this paper proposes a signal-processing software technique for the tolerance of the 4-axis strain gauge applied to a military weapon system. First, the tolerance of the strain-gauge and the signal processing circuit according to the ambient temperature were evaluated and analyzed. Second, a software technique for processing the dead zone and offset area that can improve the tolerance of the strain-gauge is proposed. The experimental results applying the software technique confirmed that it operated normally in the temperature test and operation test. Therefore, the proposed software technique is valid and can be used as useful information to improve tolerance due to ambient temperature and vibration when designing a system using a strain-gauge.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1024-1031
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• 1999

In order to transmit high-speed wide band signals efficiently in multipath fading environments, M-ary QAM signalling combined with OFDM transmission technique is applied. In this paper, the effect of synchronization error caused by carrier frequency offset and SER(Symbol Error Rate) performance of OFDM-16QAM and OFDM-64QAM are theoretically analyzed. Our result shows that as the number of sub-carrier in OFDM system increases the frequency-offset caused inter-channel interference(ICI) increases significantly, and that an error floor occurs even at high SNR of OFDM system. For OFDM-64QAM, the error floor occurs at SER=1$\times$10-7 when a normalized frequency-offset is 0.001, in which the SNR degradation is much greater than that of OFDM-16QAM. From this study the maximum allowable frequency-offset of OFDM-16QAM and OFDM-64QAM systems can be determined to meet the specific SER requirement.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.823-832
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• 2011

In this paper, an efficient blind carrier frequency offset (CFO) estimation method in orthogonal frequency division multiplexing (OFDM) systems is proposed. In the proposed method, we obtain two time different received OFDM symbols by using both the cyclic prefix and oversampling technique, and a cost function is defined by using the two OFDM symbols. We show that the cost function can be approximately expressed as a cosine function. Using a property of the cosine function, a formular for estimating the CFO is derived. The estimator of the CFO requires three independent cost function values calculated at three different points of frequency offset. The proposed method is very efficient in computational complexity since no searching operation for the minimum cost value is required. The proposed method reduces 97% of the amount of FFT computation, compared with the ML method. Unlike the conventional methods such as the ML method and the MUSIC] method, the accuracy of the proposed method is independent of the searching resolution since the closed form solution exists. The computer simulation shows that the performance of the proposed method is superior to those of the MUSIC and the ML method.

• Journal of radiological science and technology
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• v.30 no.3
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• pp.265-270
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• 2007

The purpose of this study was to evaluate the possibility of utilizing MT pulse at CE-TOF-MRA in patients with cerebral infarction. MRA using time-of-flight(TOF) technique with varying offset frequencies (0, 600, 1,200, and 1,800 Hz) magnetization transfer were performed in 10 patients with cerebral infarction at 3.0T MR scanner. CE-TOF-MRA and TOF-SPGR in normal vessel shown decreased SNR and increased CNR. The highest CNR in narrowing vessel shown at CE-TOF-MRA using 600 and 1,200 Hz offset frequencies. CNR in stenosis vessel increased dependent on using offset frequencies. The occlusion was clearly shown, and the highest CNR in occlusion shown at CE-TOF-MRA using 1,800 Hz offset frequencies. There was no shape variation in narrowing vessel or no visualizing vessel.