• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.1
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• pp.17-24
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• 2004

The starter of the turbo generator is composed of a high speed generator(HSG), an inverter and a boost converter instead of a gearbox, a DC motor and a low-voltage battery in the starter of the turbo shaft generation system. Because turbo generator is needed a high speed motoring at start-up, high speed generator has a low leakage inductance and inverter need a high DC link voltage. In this study, for developing the stater of a turbo generator, a boost converter with a high capacity was developed to convert high voltage from a low battery voltage. And for controlling a high frequency current to be injected to a motor winding with a low leakage inductance, the inverter with a high precision and a high speed operation was designed and for a stable ignition, the starting algorithm of a turbo generator was proposed. Turbo generator was started by the starter developed to verify the performances.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.572-579
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• 2010

Filtered multi-tone (FMT) is a form of multicarrier modulation utilizing frequency-domain equalization efficient in multi-path fading channels. Doppler frequency information can be employed for channel estimation and link adaptation to improve the performance. However, most previous studies have concentrated on the orthogonal frequency division multiplexing (OFDM) instead of FMT. Moreover, they have not considered the synchronization error that can commonly occur in practical systems. In this paper, we propose Doppler frequency estimation scheme that is effective in FMT systems with residual synchronization error and high noise levels.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.826-841
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• 2018

The military satellite communication of ROK military, ANASIS is designed for analog data such as voice and streaming data. ANASIS cannot fully support ALL-IP communications due to its long propagation delay. The next generation satellite communication system is being designed to overcome the limitation. Next generation satellite communications system considers both high-speed and low-speed networks to support various operating environment. The low-speed satellite supports both broadband and narrow-band communication. This network works as the infrastructure for of wide-area internetworking over multiple AS's in the terrestrial network. It requires minimum satellite frequency and minimum power and works without PEP and router. In this paper, we propose a network operation structure to enable the inter-operation between high and low-speed satellite networks. In addition, we propose a data link protocol for low speed satellite networks.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.7
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• pp.524-538
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• 1989

A new bilateral series resonant inverter and its control method are proposed. The proposed inverter consists of zero current switched cycloconverter. Output voltage is regulated by modulating the average magnitude of resonant current sinusoidally. Cycloconverter synthesizes low frequency output voltage from high frequency resonant current pulses. In the proposed inverter, bidirectional power flow in possible and isolation transformer is miniaturized. The proposed control method is verified through simulation and experiment. The proposed inverter will satisfy the small size and low cost requirements of small Uninterruptible Power Supply (UPS) of less than 1 KVA suitable for micro-computers and electronic equipments used in office and home automation.

• Journal of Power Electronics
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• v.18 no.2
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• pp.547-557
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• 2018

This work proposes a control method of frequency stabilization for grid integration of large-scale wind farms via the voltage source converter-based high-voltage direct current (VSC-HVDC) technology. First, the topology of grid integration of a large-scale wind farm via the VSC-HVDC link is provided, and simple control strategies for wind turbines, wind farm side VSC (WFVSC), and grid side VSC are presented. Second, a mathematical model between the phase angle of WFVSC and the frequency of the wind farm is established. The control principle of the large-scale wind power integrated system is analyzed in theory in accordance with the mathematical model. Third, frequency and AC voltage controllers of WFVSC are designed based on the mathematical model of the relationships between the phase angle of WFVSC and the frequency of the wind farm, and between the modulation index of WFVSC and the voltage of the wind farm. Corresponding controller structures are established by deriving a transfer function, and an optimization method for selecting the parameters of the frequency controller is presented. Finally, a case study is performed under different operating conditions by using the DIgSILENT/PowerFactory software. Results show that the proposed control method has good performance in the frequency stabilization of the large-scale wind power integrated system via the VSC-HVDC technology.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.146-153
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• 2008

In this paper, a integrated phase-locked loop(PLL) as a clock multiphase generator for a high speed serial link is designed. The designed PLL keeps the same bandwidth and damping factor by using programmable current mirror in the whole operation frequency range. Also, the close-loop transfer function and VCO's phase-noise transfer function of the designed PLL are obtained with circuit netlists. The self impedance on board-mounted chip is calculated according to sizes and positions of decoupling capacitors. Especially, the detailed self-impedance analysis is carried out between frequency ranges represented the maximum gain in the close-loop transfer function and the maximum gain in the VCO's phase noise transfer function. We shows PLL's jitter characteristics by decoupling capacitor's sizes and positions from this result. The designed PLL has the wide operating range of 0.4GHz to 2GHz in operating voltage of 1.8V and it is designed 0.18-um CMOS process. The reference clock is 100MHz and PLL power consumption is 17.28mW in 1.2GHz.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.175-181
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• 2006

This paper addresses an in-depth analysis of the stratosphere-to-Earth co-channel interference produced by high-altitude platforms (HAPs) and proposes a new methodology for the evaluation of its impact to terrestrial systems in terms of fractional degradation in performance, taking into account parameters such as HAP's mobility, realistic distribution of azimuth and elevation angles of the terrestrial microwave links (TMLs), and gradual high-altitude platform network (HAPN) loading. Simulations performed for different HAPN configurations, prove that the implementation of the methodology proposed, may lead to a more efficient use of the spectrum shared between the two services.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.1
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• pp.33-38
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• 1997

Generally, various semiconductor switching devices for power systems are used in battery chargers for electric vehicle. When these used, it takes the problems of transient-current or distortion of waveforms in power systems near by battery chargers because of harmonics and large peak-current, low power factor, etc., caused by the non-linearity of these devices. Recently, power factor control, line current peak-cut, harmonics reduction which was ignored in past is more and more important. In this paper, to solve those problems we will improve the characteristics of voltage rising and propose the high power factor converter circuit for battery chargers. Our proposed system convert commutated voltage to AC resonant wave in high frequency inverter and rectify the link voltages passed high-frequency transformer and transfer the DC voltages. Especially, the effect using these converter system can be improved very large by power factor control and we have to verify the possibilities of improvement through the experiment of Pb-Acid battery application.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.607-613
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• 2015

In order to design M/W(microwave) short backhaul above 10 GHz to meet the increase in mobile traffic demand, the rain attenuation as well as the atmospheric conditions such as Earth bulge and Fresnel zone should be considered. In this paper, the path lengths have been estimated theoretically in various frequency bands using the Korean standard rain rate, and an example of path profile has been analyzed in urban area utilizing spectrum management intelligence system (SMIS). These derived minimum path lengths in various frequency bands are compared to the foreign them, and then will be proposed to improve the Korean minimum path length unitized to 10 km. This paper will provide useful information for microwave engineers in designing a M/W access link, and be utilized to make an efficient usage of high frequency bands for the short mobile broadband backhaul.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.37-44
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• 2011

This paper presents the method of improving the data rate and BER in the inductive coupling link using a BPM signaling method. A complementary switching transmitter is used to remove invalid glitches at transmitted data, and the concept of pre-distortion is introduced to optimize received data. Also, an integrating receiver is used to increase the sampling margin and equalizing transistors are added in the pre-charge path of the integrator and comparator for high frequency operation. The transceiver designed with a 0.13 um CMOS technology operates at 2.4 Gb/s and consumes 5.99 mW from 1.2 V power supply.