• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.3
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• pp.413-420
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• 2010

An Estimation of VHF data link range for EW(Electronic Warfare) equipment in the sea environment was studied to predict the data link range between transmitting and receiving station. The theoretical estimation predicts within 3% error with actual measurement of VHF data link range at sea. Data link range factors including refraction and reflection are added in the basic wave propagation equation. The effect of refraction and reflection to the range is analysed with quantity level.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1243-1253
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• 2007

Recently UHF RFID system has drawn a great deal of attention because of its potential to revolutionize supply chain management. An important characterization of the performance of a RFID system is 'interrogation range', which is defined as the maximum distance between a reader and a tag. Forward-link interrogation range is defined as the maximum distance from which the tag receives just enough power to turn on and back-scatter, and reverse-tink interrogation range is the maximum distance from which the reader can detect this back-scattered signal. A link balance has to be found between the two interrogation ranges. In this paper, the interrogation range equations are formulated in both forward-link and reverse-link and a trade-off between the two values is investigated in order to maximize the interrogation range. As a result, it is observed that the gain of the reader antenna, the isolation of the circulator, and the phase noise of the local oscillator with range correlation effect mainly determine the reverse-link interrogation range.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.2 s.332
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• pp.9-16
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• 2005

The performance of satellite range measurement using tone method was analyzed in the presence of satellite link AWGN. The phase errors in range measurement are generated by AWGN of satellite up- and down-link and the degradations of satellite range measurement are dependent on the transmission mode and loop bandwidth of satellite measurement system. The analyzed effects for satellite measurement in presence of satellite link noise were also analyzed with the measured satellite range data via satellite range measurement system operating in satellite link AWGN. In RAU mode, the satellite range differences of 14.4 to 40.6 m were occurred according to the loop bandwidth of satellite range measurement system and the degradation of 0.3 dB compared with theoretical value was generated under condition of the signal-to-noise ratio of 43 dB. In RAU and TM mode, the performances of range measurement were approximately agreed to the that of RAU mode. In order to get the equal performance characteristics with RAU mode, the signal-to-noise ratio of satellite link for RAU and TM mode should be increased by signal power of 2.3 dB, which is a power loss due to transmission of telemetry signal.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.330-334
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• 2014

In this paper, we present an incoherent dual-parallel modulation linearized optical link employing two different optical wavelengths. Comparing with previous dual-parallel modulation, this linearization method prevents the recreation of distortion products and can be readily implemented. Furthermore, a dual-wavelength dual-parallel modulation linearized optical link constructed with the commercially available devices is experimentally demonstrated with a spurious-free dynamic range of $122.5dB.Hz^{4/5}$. More than 25 dB suppression of the intermodulation distortion, 15.6 dB improvement of spurious-free dynamic range and 1.5 dB improvement of compression dynamic range are achieved after linearization.

• Journal of electromagnetic engineering and science
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• v.9 no.1
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• pp.39-45
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• 2009

In this paper, we discuss hardware design and deployment issues in current passive UHF RFID systems. Using the link budget concept, the methodology to calculate forward- and reverse-link interrogation range is shown. Then, we consider hardware issues: phase diversity, phase noise with range correlation, and TX leakage problems. Finally, three interference problems when deploying RFID systems are presented.

• ETRI Journal
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• v.40 no.1
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• pp.101-110
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• 2018

In wireless positioning systems using range measurements non-line-of-sight (NLOS) links cause estimation errors. Several studies have attempted to improve the positioning performance by mitigating these NLOS errors. These studies, however, have focused on the performance of a dataset consisting of three or more links. Therefore, measurement errors induced by links are averaged, and a reliable link is not fully utilized in the dataset. This paper proposes a Link Reliability based on Range Measurement (LRRM) scheme, which specifies the relative reliability of each link using residuals. The link reliability becomes the input to a Link Residual Weighting (LRW) scheme, which is also proposed as a weighted positioning scheme. Moreover, LRRM and LRW constitute new turbo positioning, where the estimation errors are reduced considerably by iterative updates.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.10
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• pp.708-711
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• 2000

Sensorless PMSM is much studied for the industrial applications and home appliances because a mechanical sensor reduce reliability and increase cost. Most of sensorless algorithms are based on motor equations, and so the magnitude of phase voltage and current should be exactly obtained. However, the inverter output voltage applied to PMSM has relatively large error in the low speed range, and a relatively poor response is shown in the low speed range. This paper investigates the improved performance of sensorless PMSM in the low speed range. This paper proposes the error reduction of inverter output voltage which is realized through the variable link voltage. The proposed algorithm is verified through simulation and experiment.

• Ocean Systems Engineering
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• v.8 no.1
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• pp.33-39
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• 2018

The paper presents a numerical underwater channel model developed in MATLAB for estimating the optical link budget between a light emitting diode (LED) based optical transmitter and a photo diode (PD) receiver when operated in the harbor, coastal and deep waters locations in the Bay of Bengal. The water samples are collected at different locations in the Bay of Bengal using a water sampler during an offshore research cruise. The optical attenuation, the main inherent parameter determining the range of the optical communication link is identified for the different waters using an underwater irradiance measurement system in the laboratory. The identified parameters are applied to the numerical model and found that a 10 W LED and a photo diode based system can provide the optical budget required for a horizontal underwater communication range of about 0.5, 14 and 35 m in the harbor, coastal and deep waters locations respectively. By increasing the transmitter power to 50 W, the operating range of the communication link could be increased up to 53 m in deep water locations in the Bay of Bengal.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.5
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• pp.577-584
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• 1999

In this paper, the double inverted pendulum having a single actuator is built and the controller for the system is proposed. The lower link of the target pendulum system is hinged on the plate to free for rotation in the specified range($10^{\cire}$) on the x-z plane. The upper link is connected to the lower link through a DC motor. The double inverted pendulum built can be kept upright posture by controlling the position of the upper link even though it has no actuator in lower hinge. The algorithm to control the inverted pendulum consists of a state feedback controller within a linearizable range and a fuzzy logic controller coupled with a nonlinear feedback compensator for the rest of the range. Conventional state feedback control is employed, and the fuzzy controller is responsible for generating the reference joint angle of the upper link for the nonlinear feedback compensator which drives a DC motor to generate an indirect torque to the lower joint. As a result, we can get the upright posture of the proposed pendulum system. Simulations and experiments are conducted to show the validity of the proposed controller.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1656-1663
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• 2016

A capacitive wireless power transfer (C-WPT) system uses an electric field to transmit power through a physical isolation barrier which forms a pair of ac link capacitors between the metal plates. However, the physical dimension and low dielectric constant of the interface medium severely limit the effective link capacitance to a level comparable to the main switch output capacitance of the transmitting circuit, which thus narrows the soft-switching range in the light load condition. Moreover, by fundamental limit analysis, it can be proved that such a low link capacitance increases operating frequency and capacitor voltage stress in the full load condition. In order to handle these problems, this paper investigates optimal design of double matching transformer networks for C-WPT. Using mathematical analysis with fundamental harmonic approximation, a design guideline is presented to avoid unnecessarily high frequency operation, to suppress the voltage stress on the link capacitors, and to achieve wide ZVS range even with low link capacitance. Simulation and hardware implementation are performed on a 5-W prototype system equipped with a 256-pF link capacitance and a 200-pF switch output capacitance. Results show that the proposed scheme ensures zero-voltage-switching from full load to 10% load, and the switching frequency and the link capacitor voltage stress are kept below 250 kHz and 452 V, respectively, in the full load condition.