• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.40-45
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• 2007

Lightning warning system plays an important role in protecting human life and other facilities from lightning return strokes. This paper dealt with lightning positioning algorithms and circuits as a main function of lightning warning system, which monitor movements and activities of thunderclouds. Electric field component produced by lightning discharge is detected by the configuration of a whip antenna and a narrow-band resonance amplifier with center frequency of 300[kHz]. Measurement circuit of magnetic field waveform consists of a crossed-loop coil and an integral amplifier, and its frequency bandwidth is ranges from 5[kHz] to 1.2[MHz]. The polarity of lightning discharge is discriminated by electric field component. After-fixing the polarity, we can calculate the direction and distance of lightning discharge by the peak and the zero-cross time of magnetic field waveform.

• Journal of Korea Multimedia Society
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• v.9 no.12
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• pp.1669-1680
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• 2006

This paper explains that the RF systems for hi-directional wireless capsule endoscopes were designed and implemented. The designed RF systems for a capsule endoscope can transmit the images of intestines from the inside to the outside of a body and the behavior of the capsules can be controlled by an external controller simultaneously. The hi-directional wireless capsule endoscope consists of a CMOS image sensor, FPGA, LED, battery, DC to DC Converter, transmitter, receiver, and antennas. The transmitter and receiver which were used in the hi-directional capsule endoscope, were designed and fabricated with $10mm(diameter){\times}3.2mm(thickness)$ dimensions taking into the MPE, power consumption, system size, signal to noise ratio and modulation method. The RF systems designed and implemented for the hi-directional wireless capsule endoscopes system were verified by in-vivo experiments. As a result, the RF systems for the hi-directional wireless capsule endoscopes satisfied the design specifications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.4
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• pp.300-309
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• 1996

The electric and magnetic fields radiated by lightning discharges are significantly changeable in amplitude and time, one of the topics concerning electromagnetic compatibility of modern electronic systems is the efficient and economic protection against transient voltages caused by not only by direct but also by nearly lightning strokes. In this paper, in order to obtain the detailed informations about lightning electromagnetic impulse waveforms, the electric and magnetic fields radiated by lightning discharges in the summer of 1995 were measured by a fast electric antenna and a loop-type magnetic field sensor, and their charac- teristics were presented and analyzed. The signals of the electric and magnetic fields were re- corded continuously by a transient digitizer having a resolution of 12 bit and a memory capacity of 5000 point and using a sampling time of 200 ns. The electric and magnetic field waveforms associated with lightning return strokes are significantly different with those of intracloud discharges. The magnetic fields radiated by intracloud lightning discharges have essentially the same waveforms as the electric field when the lightning discharhes are at distance of 50 km or more. Also the main frequency components of the electric and magnetic fields radiated by lightning discharges range from a few kHz to several hundred kHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.1043-1049
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• 2005

In OFDM system suitable for high capacity high speed broadband transmission, ICI caused by phase noise degrades system performance seriously by destroying the orthogonality among subcarriers. In this paper, a new STFBC method combining ICI self cancellation scheme and antenna, time, frequency diversity is studied to reduce ICI effectively. CPE and ICI are analyzed by the phase noise linear approximation method in the proposed STFBC OFDM system. CIR, PICR and BER are discussed to compare the system performance degraded by phase noise of PLL. As results, STFBC method significantly reduces ICI. Furthermore, the SCI that usually happens in the traditional STBC, SFBC diversity coding method can be easily avoided.

• Journal of Sensor Science and Technology
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• v.12 no.6
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• pp.249-257
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• 2003

The bio-telemetry technologies, that use the wireless miniaturized telemetry module implanted in the human body and transmits several biomedical signal from inside to outside of the body, have been expected to solve the problem such as the patient's inconvenience and the limit for diagnosis. In the case of transceiver system using the wireless RF transmission method, the method of three-dimensional localization for implantable miniaturized telemetry module is necessary to detect the exact position of disease. A new method for three-dimensional localization using small loop antenna in the implantable miniaturized telemetry module was proposed in this paper. We proposed a method that can accurately determine the position of telemetry module by analyzing the differences in the strength of signal, which is received at each of the small size RF receiver array installed on the body surface.

• Journal of Magnetics
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• v.18 no.1
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• pp.43-49
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• 2013

A pulsed ferrite magnetic field generator (FMFG) was designed for the use in the 1000 m long through-the-earth (TTE) communication system for mining disaster situations. To miniaturize the TTE system, a ferrite core having 10,000 of permeability was used for the FMFG. Attenuation of the magnetic field intensity from the FMFG (200-turn and 0.18 m diameter) was calculated to be 89.95 dB at 1000 m depth soil having 0.1 S/m of conductivity. This attenuation was lower than 151.13 dB attenuation of 1 kHz electromagnetic wave at the same conditions. Therefore, the magnetic-field was found to be desirable as a signal carrier source for TTE communications as compared to the electromagnetic wave. The designed FMFG generates the magnetic field intensity of $1{\times}10^{-10}$ Tesla at 1000 m depth. This magnetic field is detectable by compact magnetic sensors such as flux gate or magnetic tunneling junction sensor. Therefore, the miniature FMFG TTE communication system can replace the conventional electromagnetic wave carrier type TTE system and allow reliable signal transmission between rescuer and trapped miners.

• Journal of Navigation and Port Research
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• v.40 no.6
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• pp.385-390
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• 2016

ELoran Systems can provide Position, Navigation, and Time services with comparable performance to Global Positioning Systems (GPS) as a back up or alternative system. High timing and navigation performance can be achieved by eLoran signals because eLoran receivers use "all-in-view" reception. This incorporates Time of Arrival (TOA) signals from all stations in the service range because each eLoran station is synchronized to Coordinated Universal Time (UTC). Transmission station information and the differential Loran correction data are transmitted via an additional Loran Data Channel (LDC) on the transmitted eLoran signal such that eLoran provides improved Position Navigation and Timing (PNT) over legacy Loran. In this paper, we propose a technique for adapting the delay time compensation values in eLoran timing receivers to provide precise time comparison. For this purpose, we have designed a system that measures time delay from the crossing point of the third cycle extracted from the current transformer at the end point of the transmitter. The receiver delay was measured by connecting an active H-field, an E-field and a passive loop antenna to a commercial eLoran timing receiver. The common-view time transfer technique using the calibrated eLoran timing receiver improved the eLoran transfer time. A eLoran timing receiver calibrated by this method can be utilized in the field for precise time comparison as a GNSS backup.

• Journal of Broadcast Engineering
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• v.28 no.1
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• pp.145-148
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• 2023

Open-loop Octonion space-time block code for 4 transmit antenna system is considered and random phases are applied to 4 transmit antennas for physical layer security. When an illegal hacker estimates the random phases of 1 through 4 transmit antennas with maximum likelihood (ML), this letter analyzes the bit error rate (BER) performances versus signal-to-noise ratio (SNR). And the Octonion code in the literature[1] does not have full orthogonality so, this letter employs the perfect orthogonal Octonion code. When the hacker knows that the random phases are 2-PSK constellations and he should estimate all the 4 random phases, the hacking is impossible until 100dB. When the hacker possibly know that some of the random phases, bit error rate goes down to 10^-3 so, the transmit message could be hacked.

• Journal of Korea Water Resources Association
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• v.48 no.8
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• pp.613-623
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• 2015

To overcome the difficulties of discharge measurements during flood season, MWSCM(micowave water surface current meter) which measures river surface velocities without contacting water has been applied in field work since its development. The existing version of MWSCM is for floods so that its applicability is low due to the short periods of floods. Therefore the renovative redesign of MWSCM to increase the applicability was conducted so that it can be applied to the discharge measurements during normal flows as well as flood ones by extending the measurable range of velocity. A newly developed high-performance MWSCM for general use can measure the velocity range of 0.03-20.0 m/s from flood flows to normal flows, whereas MWSCM for floods can measure the velocity range of 0.5-10.0 m/s. The improvement of antenna isolation between transmitter and receiver to block the inflow of transmitted singals to receiver and the improvement of phase noise of oscillator are necessary for detecting low velocity with MWSCM technology. Separate type antenna of transmitting and receiving signals is developed for isolation enhancement and phase locked loop synthesizer as an oscillator is applied to high-performance MWSCM for general use. Microwave frequency of 24 GHz is applied to the new MWSCM rather than 10 GHz to make the new MWSCM small and light for convenient use of it at fields. Improvement requests on MWSCM for floods-stable velocity measurement, self test, low power consumtion, and waterproof and dampproof-from the users of it has been reflected on the development of the new version of MWSCM.