• Journal of electromagnetic engineering and science
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• v.11 no.1
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• pp.16-26
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• 2011

This paper presents high power and high efficiency Doherty amplifiers for 2.345 GHz wireless broadband (WiBro) applications that use a Nitronex 125-W ($P_{3dB}$) GaN high electron mobility transistor (HEMT). Two- and three-way Doherty amplifiers and a saturated Doherty amplifier using Class-F circuitry are implemented. The measured result for a center frequency of 2.345 GHz shows that the two-way Doherty amplifier attains a high $P_{3dB}$ of 51.5 dBm, a gain of 12.5 dB, and a power-added efficiency (PAE) improvement of about 16 % compared to a single class AB amplifier at 6-dB back-off power region from $P_{3dB}$. For a WiBro OFDMA signal, the Doherty amplifier provides an adjacent channel leakage ratio (ACLR) at 4.77 MHz offset that is -33 dBc at an output power of 42 dBm, which is a 9.5 dB back-off power region from $P_{3dB}$. By employing a digital pre-distortion (DPD) technique, the ACLR of the Doherty amplifier is improved from -33 dBc to -48 dBc. The measured result for the same frequency shows that the three-way Doherty amplifier, which has a $P_{3dB}$ of 53.16 dBm and a gain of 10.3 dB, and the saturated Doherty amplifier, which has a $P_{3dB}$ of 51.1 dBm and a gain of 10.3 dB, provide a PAE improvement of 11 % at the 9-dB back-off power region and 7.5 % at the 6-dB back-off region, respectively, compared to the two-way Doherty amplifier.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.9
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• pp.936-943
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• 2013

This work presents the design and measured results of the single channel automotive radar system for 76.5~77 GHz long range FMCW radar applications. The transmitter uses a commercial GaAs monolithic microwave integrated circuit(MMIC) and the receiver uses the down converter designed using 65 nm CMOS process. The output power of the transmitter is 10 dBm. The down converter chip can operate at low LO power as -8 dBm which is easily supplied from the transmitter output using a coupled line coupler. All MMICs are mounted on an aluminum jig which embeds the WR-10 waveguide. A microstrip to waveguide transition is designed to feed the embedded waveguide and finally high gain horn antennas. The overall size of the fabricated radar system is $80mm{\times}61mm{\times}21mm$. The radar system achieved an output power of 10 dBm, phase noise of -94 dBc/Hz at 1 MHz offset and a conversion gain of 12 dB.

• The KIPS Transactions:PartC
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• v.16C no.1
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• pp.51-56
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• 2009

Time synchronization algorithm in wireless sensor networks is essential to various applications such as object tracking, data encryption, duplicate detection, and precise TDMA scheduling. This paper describes CDRS that is a time synchronization algorithm using the Clock Drift rate and Reference Signals between two sensor nodes. CDRS is composed of two steps. At first step, the time correction is calculated using offset and the clock drift rate between the two nodes based on the LTS method. Two nodes become a synchronized state and the time variance can be compensated by the clock drift rate. At second step, the synchronization node transmits reference signals periodically. This reference signals are used to calculate the time difference between nodes. When this value exceeds the maximum error tolerance, the first step is performed again for resynchronization. The simulation results on the performance analysis show that the time accuracy of the proposed algorithm is improved, and the energy consumption is reduced 2.5 times compared to the time synchronization algorithm with only LTS, because CDRS reduces the number of message about 50% compared to LTS and reference signals do not use the data space for timestamp.

• Management & Information Systems Review
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• v.32 no.3
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• pp.25-41
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• 2013

This study was designed to suggest the effective CSR strategies for MNCs operating in Chinese market. For this purpose, it compares the multi-years results for the evaluation on CSR activities of Multinational and Chinese firms. It also conducts questionnaire survey in an attempt at developing measures of Chinese publics' perception on the four dimensions of CSR defined by Research Center of Chinese Academy of Social Sciences - responsibility management, economic responsibility, social responsibility, and environmental responsibility. The findings of empirical analyses indicate that the CSR activities of MNCs much fall in all four dimensions compared with them of Chinese firms. Among four dimensions, MNCs have had bad evaluations especially on economic responsibility and social responsibility that are considered more important than the others to Chinese. Those findings imply that the MNCs has so far failed to implement effective CSR activities in China. In order to offset their liabilities of foreignness and compensate for their disadvantages in the lack of governmental supports, MNCs should intensify the CSR in economic and social responsibilities.

• Management & Information Systems Review
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• v.36 no.3
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• pp.255-268
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• 2017

This study examines whether firms with tax avoidance of Corporate Social Responsibility(CSR) performance is tempered by the extent firms engage in CEO turnovers. Considering the increasing interest in CSR activities of the firm to secure sustainable growth of national economy, this paper investigates the benefit and cost of CSR activities by combining the agency theory using the firm level data. Prior studies document that investors positively value tax avoidance. The rationale for this finding is that tax avoidance provides cash savings that can be used by firm managers to generate future shareholder wealth. Prior studies also show that investors' valuations are sensitive to the risk of future negative tax outcomes. Assuming that many types of CSR performances are low risk, low yielding uses of firm resources, we posit that higher levels of CSR performance may signal to investors that cash generated via tax avoidance has not been fully used to generate a return sufficient to offset the risk associated with aggressive tax planning strategies. Consistent with this argument, we predict and find that the positive association between CSR performance and tax avoidance is significantly weakened when firms have higher positive levels of CEO turnovers. Further, we predict and find that 'philanthropic' types of CSR activities in particular are associated with investor discounting of tax avoidance. We interpret our results as suggesting the equity market views CSR activities to be ostensibly funded through cash savings generated via tax avoidance.

• Journal of the Korean Geophysical Society
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• v.2 no.3
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• pp.209-216
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• 1999

In order to get geologic information necessary for underground installation of water pipe, seismic refraction profiling was applied to the southwest side of the Seomjin River which flows between Namwon-gun, Cholabuk-do and Gokseong-gun, Cholanam-do. Before obtaining the in-line refraction data, walkaway data were recorded with 1 m geophone interval and -36∼+36 m offset range. From the walkaway data, it is interpreted that a dry soil layer with the average velocity of 585 m/s covers wet sediments with the average velocity of 1,326 m/s. The second layer overlies basements nearly horizontally with the average velocity of 4,218 m/s. Refraction profiling of 220 m long with the geophone interval of 2 m is interpreted with the Generalized Reciprocal Method (GRM). Three layers are identified with average velocities of 688 m/s, 1,473 m/s, and 3,776 m/s, respectively. The depth to the bedrock impossible for ripping ranges between two extremes, 1.51∼2.43 m and 2.25∼3.54 m, depending upon thickness of the hidden layer. A typical shortcoming of refraction method, the hidden layer problem, prevents accurate estimation in depth of the second layer.

• International Commerce and Information Review
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• v.14 no.4
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• pp.517-541
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• 2012

Since the Korea-Chile FTA in 2003, eight FTAs are now in force including Korea-EU and Korea-US FTA. The government anticipate that FTAs increase the GDP of Korea. Government-related research institutes officially reports the positive economic impact in Korea. However, the report does not show that how much Busan economy is affected by the FTAs. For this reason, we study the economic effects of FTAs in Busan. We compare the trade statistics before and after the time each FTA is in force. The resulting figures show that the exports and trades of Busan with the FTA nations increased significantly after the enforcement. For example, the exports to Chile increased by 273% when we compare the three-year average trade. We also construct an econometrics model to estimate the price elasticity. The estimated elasticity of exports for manufactured goods is 1.38 while that of imports is 0.83. Among the manufacturing industry, machinery has the highest price elasticity, 1.8. The average tariff for manufactured goods is 3.9% for FTA nations, while that is 5.8% for Busan. This higher price fall in Busan is offset by the lower price elasticity to make Busan's export increase be greater than Busan's import increase. Busan's export increases by 4.8% while import increases by 3.7%. So, it is expected to be added to the annual trade surplus of approximately $107million.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.4
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• pp.11-17
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• 2001

In this paper, we propose a polarity decision carrier recovery algorithm for high order QAM(Quadrature Amplitude Modulation), which has robust and large frequency acquisition performance in the high order QAM modem. The proposed polarity decision PD(Phase Detector) output and its variance characteristic are mathematically derived and the simulation results are compared with conventional DD(Decision-Directed) method. While the conventional DD algorithm has linear range of $3.5^{\circ}{\sim}3.5^{\circ}$, the proposed polarity decision PD algorithm has linear range as large as $-36^{\circ}{\sim}36^{\circ}$ at ${\gamma}-17.9$. The conventional DD algorithm can only acquire offsets less than ${\pm}10\;KHz$ in the case of the 256 QAM while an analog front-end circuit generally can reduce the carrier-frequency offset down to only ${\pm}100\;KHz$. Thus, in this case additional AFC or phase detection circuit for carrier recovery is required. But by adopting the proposed polarity decision algorithm, we can find the system can acquire up to ${\pm}300\;KHz$at SNR = 30dB without aided circuit.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.12
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• pp.16-21
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• 2007

In this paper, the dual-band voltage-controled oscillator (VCO) using the composite right/left-handed (CRLH) transmission line (TL) and the tunable negative resistance based on the fin diode is presented. It is demonstrated that the CRLH TL can lead to metamaterial transmission line with the dual-band tuning capability. The dual-band operation of the CRLH TL is achieved by the frequency offset and the phase slope of the CRLH TL, and the frequency ratio of the two operating frequencies can be a non-integer. Each frequency band of VCO has to operate independently, so we have used the tunable negative resistance based on the pin diode. When the forward bias has been into the pin diode, the phase noise of VCO is $-108.34\sim-106.67$ dBc/Hz @ 100 kHz in the tuning range, $2.423\sim2.597$ GHz, whereas when the reverse bias has been fed into the pin diode, that of VCO is $-114.16\sim-113.33$ dBc/Hz @ 100 kHz in the tuning range, $5.137\sim5.354$ GHz.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.53-59
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• 2008

In this paper, a novel dual-band high-efficiency class-F power amplifier using the composite right/left-handed (CRLH) transmission lines (TLs) has been realized with one RF Si lateral diffusion metal-oxide-semiconductor field effect transistor (LDMOSFET). The CRLH TL can lead to metamaterial transmission line with the dual-band tuning capability. The dual-band operation of the CRLH TL is achieved by the frequency offset and the nonlinear phase slope of the CRLH TL for the matching network of the power amplifier. Because the control of the all harmonic components is very difficult in dual-band, we have managed only the second- and third-harmonics to obtain the high efficiency with the CRLH TL in dual-band. Also, the proposed power amplifier has been realized by using the harmonic control circuit for not only the output matching network, but also the input matching network for better efficiency. Two operating frequencies are chosen at 880 MHz and 1920 MHz in this work. The measured results show that the output power of 39.83 dBm and 35.17 dBm was obtained at 880 MHz and 1920 MHz, respectively. At this point, we have obtained the power-added efficiency (PAE) of 79.536 % and 44.04 % at two operation frequencies, respectively.