• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.398-402
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• 2003

In this paper, we have analyzed the performance enhancement of OFDM/QPSK-DMR(Orthogonal Frequency Division Multiplexing/Quadrature Phase Shift Keying Modulation-Digital Microwave Radio)system using BL-PSF(Band Limited-Pulse Shaping Filter) over the microwave channel. For performance enhancement, we apply the one-tap adaptive equalizer for OFDM/QPSK-DMR system and compare with the BER performance of single carrier DMR system. Computer simulations confirm that the OFDM/QPSK-DMR system using one-tap adaptive equalizer has the same BER performance for the single carrier DMR system.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1355-1357
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• 1997

In this study, the ferrite/rubber composite microwave absorbers mixed Ni-Zn ferrite and $Ni_2Y$ ferroxplana were prepared in order to control matching condion. The variation of the material constants($\dot{\varepsilon}$, $\dot{\mu}$) and microwave absorbing characteristics were investigated with various ferrite mixing ratio. The material constants of ferrite/rubber composite microwave absorber could be controlled by variation ferrite mixing radio. The matching frequency and thickness could be controlled with various ferrite mixing ratio.

• Journal of Magnetics
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• v.2 no.1
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• pp.25-27
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• 1997

Ferrite tile absorber is of great concern for the application to anechoic chambers due to the growing demand of EMI or EMC measurements. This paper investigates the magnetic, dielectric and microwave absorbing properties of a Ni-An ferrite for the purpose. A design chart was constructed with the solutions of impedance-matching equation in the radio frequencies (30 MHz - 1 GHz). The material parameters for zero-reflection are predicted from the chart. The magnetic and dielectric properties of sintered Ni-Zn ferrite is found to be well suited for this requirements. A superior microwave absorbing properties (frequency band and absorber thickness) of the samples are demonstrated.

• Journal of Information Display
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• v.12 no.2
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• pp.109-113
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• 2011

This paper summarizes the recent fabrication and characterizations of flexible high-speed radio frequency (RF) transistors, PIN-diode single-pole single-throw switches, as well as flexible inductors and capacitors, based on single-crystalline Si nanomembranes transferred on polyethylene terephthalate substrates. Flexible thin-film transistors (TFTs) on plastic substrates have reached RF operation speed with a record cut-off/maximum oscillation frequency ($f_T/f_{max}$) values of 3.8/12 GHz. PIN diode switches exhibit excellent ON/OFF behaviors at high RF frequencies. Flexible inductors and capacitors compatible with high-speed TFT fabrication show resonance frequencies ($f_{res}$) up to 9.1 and 13.5 GHz, respectively. Robust mechanical characteristics were also demonstrated with these high-frequency passives components.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.1 s.116
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• pp.7-14
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• 2007

In this paper, the scan characteristics of phased array antenna consisted of rectangular open-ended waveguide with a triangular grid are investigated. An infinite array structure is analyzed by numerically solving the integral equation for the electric field over the waveguide aperture using waveguide mode function and Floquet mode function. Next, SEP(Scan Element Pattern) and SI(Scan Impedance) characteristics are simulated by CST's MWS(Microwave Studio) and Ansoft's HFSS(High Frequency Structure Simulator) for the finite and infinite array structures. Also, validity of these approaches is verified by comparing the calculated and simulated results with the measured ones for an $8{\times}8$ subarray. Within 10.5 % fractional bandwidth in the X-band, the fabricated subarray showed the flat gain characteristic in the scan range of ${\pm}45^{\circ}C$ in the E-plane(azimuth) and ${\pm}20^{\circ}C$ in the H-plane(elevation), and also showed the return loss characteristic of less than -10 dB.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.32.2-32.2
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• 2010

The Korean Solar Radio Burst Locator (KSRBL) is a single dish radio spectrograph, which is designed to record the spectra of microwave (0.5 - 18 GHz) bursts with 1 MHz spectral resolution and 1 s time cadence, and locate their positions on the solar disk within 2 arcmin. It was installed at KASI in 2009 August, and operational thereafter. The antenna pointing coefficients were initially determined during the installation and refined later using a series of antenna pointing calibrations. The filter to prevent the radio frequency interference around 2 GHz was designed and is to be installed. After the installation, the full frequency coverage will be recovered from the temporarily restricted frequency coverage (5 - 14 GHz). Also an effort to solve a couple of minor problems for the full performance of the system is in progress.

• Electronics and Telecommunications Trends
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• v.32 no.6
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• pp.66-72
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• 2017

The frequency range of a radio wave is from 3kHz to 300GHz, and radio technologies use this range to improve the quality of human lives. Radio technologies have entered a new phase of communication. The core infrastructure used as the basis for technologies leading the fourth industrial evolution, such as artificial intelligence, the Internet of Things, autonomous cars/drones, augmented reality, robots, and remote medical diagnoses, is the 5G network. The 5G network enables transmitting and receiving large amounts of data at very high speed. In particular, application technologies with artificial intelligence have been studied, including radar, wireless charging, electromagnetic devices and their effects on humans, EMI/EMC, and microwave imaging. In this study, we present a future radio technology that is needed to prepare for the upcoming industrial revolution and digital transformation.

• Journal of The Korean Astronomical Society
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• v.38 no.4
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• pp.445-462
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• 2005

In a companion paper, we have presented so-called Spatio-Spectral Maximum Entropy Method (SSMEM) particularly designed for Fourier-Transform imaging over a wide spectral range. The SSMEM allows simultaneous acquisition of both spectral and spatial information and we consider it most suitable for imaging spectroscopy of solar microwave emission. In this paper, we run the SSMEM for a realistic model of solar microwave radiation and a model array resembling the Owens Valley Solar Array in order to identify and resolve possible issues in the application of the SSMEM to solar microwave imaging spectroscopy. We mainly concern ourselves with issues as to how the frequency dependent noise in the data and frequency-dependent variations of source size and background flux will affect the result of imaging spectroscopy under the SSMEM. We also test the capability of the SSMEM against other conventional techniques, CLEAN and MEM.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.489-498
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• 2003

Recently to introduce new services of ultra-high speed wireless access and systems beyond the 3rd generation mobile communication, 5 GHz band has been highly interested. As a way of getting the required frequency, it is considered that microwave relay bands below 6 GHz, which shows a slow decrease in demand and less cost-effectiveness, should be moved to other bands above 6 GHz. In this paper, as a tool for analyzing microwave link design and its service quality, the outage prediction based upon Vigants & Barnett＇s model is reviewed. To show outage and availability calculation, simulations are performed for the operating 4 GHz radio sites, and some results and features regarding frequency movement to 6.7 as well as 8 GHz are also discussed in terms of diversity techniques, bit error rate, and availability As the results, it is confirmed that only the diversity techniques of space or space and frequency can satisfy the annual objective of availability irrespective of frequency movement.

• Journal of Astronomy and Space Sciences
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• v.32 no.1
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• pp.91-99
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• 2015

The Korean Solar Radio Burst Locator (KSRBL) is a solar radio spectrograph observing the broad frequency range from 0.245 to 18 GHz with the capability of locating wideband gyrosynchrotron bursts. Due to the characteristics of a spiral feed, the beam center varies in a spiral pattern with frequency, making a modulation pattern over the wideband spectrum. After a calibration process, we obtained dynamic spectra consistent with the Nobeyama Radio Polarimeter (NoRP). We compared and analyzed the locations of bursts observed by KSRBL with results from the Nobeyama Radioheliograph (NoRH) and Atmospheric Imaging Assembly (AIA). As a result, we found that the KSRBL provides the ability to locate flaring sources on the Sun within around 2'.