• Proceedings of the KIEE Conference
• /
• 2003.07c
• /
• pp.1776-1778
• /
• 2003

Partial Discharge(PD) pulses propagate in gas insulated substation(GIS) with rise time shorter than one nanosecond. Therefore, Ultra high frequency(UHF) couplers which have ultra wide band(UWB) characteristics from hundreds of MHz to several GHz are desirable for the detection of the PB pulses in GIS. In this paper, the authors proposed a log-periodic antenna for GIS PD detection. Various parameters of the coupler such as frequency bandwidth, coupler gain, radiation pattern, coupler geometry were considered through the simulations and the experiments together.

• Journal of Digital Convergence
• /
• v.11 no.11
• /
• pp.85-94
• /
• 2013

This paper presents a novel mobile measurement system with multi antennas which enable mobile measurement as well as fixed measurement with telescope mast. Proposed system installed 4 omni directional antennas for the space diversity process and one directional log periodic antenna for the simultaneous conventional fixed measurement. Whole antenna systems are connected to the custom DTV channel analyzers with Ethernet networks respectively and processed by the main controller to calculate real time average receive levels. To prove the performance of proposed system, the typical receive models are categorized as 3 area types - open area, building area and house area, and then intensive field tests were performed through mobile and fixed measurement phases. With these measurement data, the relationships between mobile and fixed measurement are analyzed, and the concept of compensation factor is proposed to assume the average receive level of signal. The field test is fulfilled as a co-work with public broadcasters and the proposed system is applied to the intensive coverage measurement projects for metropolitan areas by the korean government agencies.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.11
• /
• pp.1004-1011
• /
• 2016

In this paper, we suggested the methodology of analyzing and reconstructing of measured electromagnetic emanations from the Micro Controller Unit(MCU) chip of Universal Serial Bus(USB) keyboard. By analyzing electromagnetic emanations, entered information is found at keystroke and furthermore, information security problems such as personal information leakage and eavesdropping can be arisen. USB keyboards make the radiated signal according to the signal transmission mechanism. Electromagnetic emanations were measured by log periodic antenna and wideband receiver and were analyzed by signal processing algorithm.

• ETRI Journal
• /
• v.38 no.4
• /
• pp.665-674
• /
• 2016

We designed and fabricated a semiconductor optical amplifier-integrated dual-mode laser (SOA-DML) as a compact and widely tunable continuous-wave terahertz (CW THz) beat source, and a pin-photodiode (pin-PD) integrated with a log-periodic planar antenna as a CW THz emitter. The SOA-DML chip consists of two distributed feedback lasers, a phase section for a tunable beat source, an amplifier, and a tapered spot-size converter for high output power and fiber-coupling efficiency. The SOA-DML module exhibits an output power of more than 15 dBm and clear four-wave mixing throughout the entire tuning range. Using integrated micro-heaters, we were able to tune the optical beat frequency from 380 GHz to 1,120 GHz. In addition, the effect of benzocyclobutene polymer in the antenna design of a pin-PD was considered. Furthermore, a dual active photodiode (PD) for high output power was designed, resulting in a 1.7-fold increase in efficiency compared with a single active PD at 220 GHz. Finally, herein we successfully show the feasibility of the CW THz system by demonstrating THz frequency-domain spectroscopy of an ${\alpha}$-lactose pellet using the modularized SOA-DML and a PD emitter.

• Journal of Astronomy and Space Sciences
• /
• v.37 no.2
• /
• pp.143-156
• /
• 2020

Korea Polar Research Institute (KOPRI) installed an ionospheric sounding radar system called Vertical Incidence Pulsed Ionospheric Radar (VIPIR) at Jang Bogo Station (JBS) in 2015 in order to routinely monitor the state of the ionosphere in the auroral oval and polar cap regions. Since 2017, after two-year test operation, it has been continuously operated to produce various ionospheric parameters. In this article, we will introduce the characteristics of the JBS-VIPIR observations and possible applications of the data for the study on the polar ionosphere. The JBS-VIPIR utilizes a log periodic transmit antenna that transmits 0.5-25 MHz radio waves, and a receiving array of 8 dipole antennas. It is operated in the Dynasonde B-mode pulse scheme and utilizes the 3-D inversion program, called NeXtYZ, for the data acquisition and processing, instead of the conventional 1-D inversion procedure as used in the most of digisonde observations. The JBS-VIPIR outputs include the height profiles of the electron density, ionospheric tilts, and ion drifts with a 2-minute temporal resolution in the bottomside ionosphere. With these observations, possible research applications will be briefly described in combination with other observations for the aurora, the neutral atmosphere and the magnetosphere simultaneously conducted at JBS.

• Journal of The Korean Astronomical Society
• /
• v.42 no.1
• /
• pp.1-7
• /
• 2009

The e-CALLISTO is a global network of frequency-agile solar radio spectrometers that was constructed in a collaboration between Swiss Federal Institute of Technology Zurich (ETH Zurich) and local host institutes. It is intended to monitor solar radio bursts 24 hours a day in frequency range between 45 MHz and 870 MHz. One of e-CALLISTO spectrometer was installed at Korea Astronomy and Space Science Institute (KASI) in 2007 October. The spectrometer gets signals from a horizontally polarized log-periodic antenna mounted on an automatic Sun-tracking system. Tracking status and data are monitored in Space Weather Monitoring Laboratory (SWML) of KASI in real time, and flare time data are transferred to ETH Zurich data archive daily. Using this spectrometer we obtained a couple of type II solar radio bursts on 2007 December 31, and found that these bursts are associated with a CME which occurred on the east limb.