• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.8
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• pp.632-639
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• 2018

This paper presents a single antenna radar sensor with a Ku-band radar transceiver IC realized by 130 nm CMOS processes. In this radar receiver, sensitivity time control using a DC offset cancellation feedback loop is employed to achieve a constant SNR, irrespective of distance. In addition, the receiver RF block has gain control to adjust high dynamic range. The RF output power is 9 dBm and the full chain gain of the Rx is 82 dB. To reduce the direct-coupled Tx signal to the Rx in a single antenna radar, a stub-tuned hybrid coupler is adopted instead of a bulky circulator. The maximum measured distance between the horn antenna and a metal plate target is 6 m.

• Journal of Drive and Control
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• v.12 no.3
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• pp.52-59
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• 2015

An electro hydraulic poppet valve (EHPV) and a variable orifice poppet are assembled in a single block, which is referred to as a RHINO but is also generally called a pilot-operated flow control valve. In this study, we analyzed the structure and the operating principle for a RHINO applied in a 21-ton electric excavator system. The RHINO was experimentally tested to measure the dynamic responses and the pressure energy loss. In this test, we investigated the variation in the conductance coefficient according to the increase in the supply pressure under a constant current and a variation in the flow rate according to the increase in the current. Then, the geometrical shapes and the spring stiffness of the RHINO were considered to develop an analysis model. The characteristics (current-force and hysteresis) for the solenoid based on the experimental data were reflected in the analysis model that was developed, and the reliability of the analysis model was also verified by comparing the experimental and analytical results. The developed model is thus considered to be reliable for use in a wide range of applications, including optimum design, sensitivity analysis, parameter tuning, etc.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.3
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• pp.274-284
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• 2003

Multi-level converter that is high-capacity electric power conversion system is used widely to electric motor drive system and FATCs(Flexible AC Transmission Systems). H-Bridge converter has been prevalently applied to shunt-type system because it can be easily expanded to the multi-level. In steady states, converter is normally operated in the range of 0.7∼0.8 of modulation Index. Even though zero vectors are not imposed to high modulation index, DC-Link voltage Is constant. It means that converter has another boost vector except for zero vectors among several vectors in 3-level converter. This paper has examined the principle of boost vector and investigated the difference between another boost vector and zero vectors in 3-level converter. In addition, this paper has analysed and compared the charging currents and the capacitor voltages of two topologies. The currents and voltages are related to reference voltage. Therefore, it proposed the calculation method for the voltage ripple and the charging current of each capacitor and compared various DC-Link voltage control methods through the simulation.

• Journal of Communications and Networks
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• v.15 no.5
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• pp.476-485
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• 2013

In this paper, the effective capacity of a multiple-input multiple-output (MIMO) system in two different cases with receive antenna selection (RAS) and transmit antenna selection (TAS) schemes is investigated. A closed-form solution for the maximum constant arrival rate of this network with statistical delay quality of service (QoS) constraint is extracted in the quasi-static fading channel. This study is conducted in two different cases.When channel state information (CSI) is not available at the MIMO transmitter, implementation of TAS is difficult. Therefore, RAS scheme is employed and one antenna with the maximum instantaneous signal to noise ratio is chosen at the receiver. On the other hand, when CSI is available at the transmitter, TAS scheme is executed. In this case, one antenna is selected at the transmitter. Moreover, an optimal power-control policy is applied to the selected antenna and the effective capacity of the MIMO system is derived. Finally, this optimal power adaptation and the effective capacity are investigated in two asymptotic cases with the loose and strict QoS requirements. In particular, we show that in the TAS scheme with the loose QoS restriction, the effective capacity converges to the ergodic capacity. Then, an exact closed-form solution is obtained for the ergodic capacity of the channel here.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1065-1071
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• 2012

Wind energy is becoming one of the most preferable alternatives to conventional sources of electric power that rely on fossil fuels. For stable electric power generation, constant rotating speed control of a wind turbine is performed through pitch control and stall control of the turbine blades. Recently, variable pitch control has been implemented in modern wind turbines to harvest more energy at variable wind speeds that are even lower than the rated one. Although wind turbine pitch controllers are currently optimized using a step response via the Ziegler-Nichols auto-tuning process, this approach does not satisfy the requirements of variable pitch control. In this study, the variable pitch controller was optimized by a genetic algorithm using a neural network model that was constructed by the Latin Hypercube sampling method to improve the Ziegler-Nichols auto-tuning process. The optimized solution shows that the root mean square error, rise time, and settle time are respectively improved by more than 7.64%, 15.8%, and 15.3% compared with the corresponding initial solutions obtained by the Ziegler-Nichols auto-tuning process.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.2
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• pp.29-36
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• 2000

The principle and design of two-stage CMOS operational amplifier with rail-to-rail input and class-AB output stage is presented. The rail-to-rail input stage shows almost constant transconductance independent of the common mode input voltage range in global transistor operation region. This new technique does not make use of accurate current-voltage relationship of MOS transistors. Hence it was achieved by using simple linear relationship of currents. The simulated transconductance variation using SPICE is less the 4.3%. The proposed global two-stage opamp can operate both in strong inversion and in weak inversion. Class AB output stage proposed also has a full output voltage swing and a well-defined quiescent current that does not depend on power supply voltage. Since feedback class- AB control is used, it is expected that this output stage can be operating in extremely low voltage. The variation of DC-gain and unity-gain frequency is each 4.2% and 12%, respectively.

• Journal of the Korean Magnetics Society
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• v.13 no.6
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• pp.251-256
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• 2003

We have developed the quality analysis system for magnetic field effect of cathode-ray tube that is used a monitor, TV and medical appliance. We designed and constructed the large 3-axis square coil (2 m length) system for the generation of 3-component magnetic field using power supply, magnetometer and computer below 0.2 mT range. The coil constant is 30.31 ${\mu}$T, 29.73 ${\mu}$T and 30.51 ${\mu}$T for the X, Y and Z axis square coil respectively. The magnetic field resolution was 0.01 T. The uniformity of magnetic field was measured within 1 ％ in the range of 12 cm.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1219-1226
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• 2017

In this paper, it is performed the optimal design of the UV LED bar which can be used variously. The UV LED Bar emits ultraviolet rays, so it is important to emit ultraviolet rays constantly for the purpose of use. In order to emit a certain amount of ultraviolet rays as ever, the ultraviolet ray emission should be driven by a constant current source within the operable input voltage range. And also the heat dissipation is particularly important because of the long ultraviolet emission retention time due to the UV utilization characteristics. In addition, since human body protection is essential, the algorithm is configured to operate according to human body detection using distance sensor and Bluetooth. Three 365nm UV LEDs were used in series to emit ultraviolet UVA, operating at the constant current of 500mA with an efficiency of 87.5% and a power consumption of 6.006W. The ultraviolet radiation dose was measured at $5.35mW/cm^2$ at the distance of 10 cm when measured by the Lutron ultraviolet measuring instruments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.231-236
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• 2016

The stability of DGPS signal in the DGPS service area was measured and the service availability according to the receiving signal strength was analyzed in this paper. Based on the effects of radio wave propagation in the seasons of winter and summer, daytime and night, the method to provide the DGPS service coverage was presented in this paper. The signal's strength of DGPS radio wave were measured at a constant distance from the DGPS reference station during a constant period. The propagation of DGPS radio wave is affected by status of ground conductivity, so the DGPS service area is dependant on the ground conductivity. To provide the stable service coverage, it is necessary to apply the adaptive power control for receiving signal's variations and the antenna design for alleviation of high elevation's radiation.

• Smart Media Journal
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• v.13 no.1
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• pp.52-59
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• 2024

This paper proposes a plan to improve the reception radio environment of the mobile terminal and maintain a constant reception electric field by using small cells in a small closed environment. In order to configure an efficient communication infrastructure for small cells, both ends of wireless transmission and reception of an Ethernet-based wireless video recording system are connected using an L2 switch. The small cell connected to the receiving side L2 switch shares the wireless network section of the wireless video recording system and connects to the transmitting side L2 switch. After that, when it is normally linked to FMS, a management system for small cells, through the Internet network, the output of small cells is checked. In order to verify the results, a proposed network is formed on the elevator inside the building with a poor radio wave environment, and the radio wave environment is measured before and after the small cell application in the section where the elevator operates. As a result, the main parameters of the radio wave environment in all sections of the elevator are improved, as well as a constant receiving electric field strength within the moving elevator.