• Journal of electromagnetic engineering and science
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• v.15 no.1
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• pp.59-61
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• 2015

A wideband H-band detector operating near 300 GHz has been developed based on SiGe HBT technology. The detector consists of an on-chip antenna and a HBT differential pair for square-law detection. It showed responsivity of more than 1,700 V/W and noise equivalent power (NEP) smaller than $180pW/Hz^{0.5}$ for the measured frequency range of 250-350 GHz. The maximum responsivity and the minimum NEP were 5,155 V/W and $57pW/Hz^{0.5}$, respectively; both were obtained at 330 GHz with DC power dissipation at 9.1 W.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.28-30
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• 2002

The PD in GIS leads to a charge transfer and a voltage drop across the discharge area. They cannot be measure directly but we can measure electromagnetic wave made by PD. In generally, compared with VHF band, electromagnetic waves of UHF band have a low noise therefore, we can detect the real defect with several pC in GIS using UHF method. In this paper, the U-slot microstrip patch antenna for measuring PD signal in GIS is presented. the proposed UHF sensor are designed to have large band characteristics and unaffected structure for GIS operation.

• Journal of the Korea Society of Computer and Information
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• v.11 no.3
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• pp.213-219
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• 2006

Interference occurs by signals received from directions that were different from the signals of the users in a mobile communication system. Various studies have been undertaken, including diversity, equalizer, etc., in order to reduce interference. In this study, the weighted value of the array antenna was obtained to improve signal-to-noise ratio. The weighted value was obtained as an eigen value and an eigen vector by using the correlation coefficient of the signal. The weighted value obtained was then applied to the CDMA system to increase system performance and capacity. Both QPSK and OQPSK modulation systems were applied to analyze performance.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.4
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• pp.467-474
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• 2019

Recently, optical phased array(OPA) based laser detection and ranging(LADAR) has gained great interest to replace the traditional mechanical light detection and ranging technique(LiDAR). In OPA-based LADAR, it is well known that phases of laser pulses traveling through each of channels should be the same to obtain a narrow free-space single beam without noise-like ripples in the far field. However, it is difficult to provide such ideal condition due to the fabrication errors. To tackle this problem, any algorithms should be necessary to compensate the initial random phases of each channel in OPA antenna. In this paper, we propose a hill-climbing based phase calibration algorithm and evaluate the performance of the proposed algorithm.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.370-375
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• 1987

In this study, the Rayleigh fast fading simualtors encountered in channel modelling of mobile radio have been implemented and evaluated. Two models used for the fading environment were frequency composition of phase modulated signals and shaping spectrum of noise sources with filters. The spectrum chosen for our purpose is appropriate to an omnidirectional antenna. From results of the experiment with various parameters, we have obtained satisfying results which are closely agreed to theoretical values.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.27 no.2
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• pp.109-122
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• 2023

In this study, we consider the application of the bifocusing method (BFM) for identifying the locations and shapes of small anomalies from scattering parameter data when the exact values of background permittivity and conductivity are unknown. To this end, an imaging function using numerical focusing operator is introduced and its mathematical structure is revealed by establishing a relationship with an infinite series of Bessel functions, antenna arrangements, and anomaly properties. On the basis of the revealed structure, we demonstrate why inaccurate location and size of anomalies were retrieved via the BFM. Some simulation results are illustrated using synthetic data polluted by random noise to support the theoretical result.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.152-157
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• 2006

In this paper, we have analyzed the effects of interference from HAPS ground stations to P-MP FWA base station and to P-MP FWA terminal station using more detail parameters such as a new interference model, a realistic HAPS scenario, practical antenna patterns for both the HAPS system and FWA systems. The analysis results show that, in the case of interference from HAPS GSs into a P-MP BS, compatibility of the two systems can be obtained by using a sectored BS antenna with the boresight directed away from the nadir. However, in the case of interference from HAPS GSs into a P-MP TS, the two systems cannot operate effectively in the same band unless the separation distance is guranteed and/or some form of interference mitigation technique is employed such as dynamic channel allocation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.3
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• pp.186-194
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• 2017

In this paper, we analyze the main performance of satellite's Synthetic Aperture Radar system for high resolution and wide swath. We have used the radiation pattern of reflector antenna with array feed and comparison between the conventional ScanSAR mode and SweepSAR mode has been carried out. The SweepSAR mode is a high-resolution wide-swath mode that transmits beams over a wide range and receives echo signals through sequential beamforming based on SCORE(SCan On REceive). In this paper, we analyzed the operating principle and characteristics of satellite's SweepSAR mode and simulate system performances. In addition, in order to increase the utilization of image, performances analysis for multiple frequency bands(C-band, X-band) has been considered.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.52-57
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• 2016

We introduce a hybrid scheduling in a multi-path poor scattering full-duplex (FD) system, which consists of one multi-antenna FD base station and a large number of single-antenna half-duplex mobile stations. Our hybrid scheduling utilizes partial channel state information at the transmitter. In particular, unlike the conventional scheduling method using opportunistic transmission for both uplink and downlink, the proposed scheme combines a random transmit beamforming for downlink and a zero forcing beamforming for uplink. As our main result, via computer simulations, it is shown that the proposed scheme has a superior sum-rate performance than that of the conventional scheduling method beyond a certain signal-to-noise ratio regime.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.335-339
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• 2018

The optical characteristics of a terahertz (THz) antenna-coupled bolometer (ACB) detector were evaluated using a pulsed quantum cascade laser (QCL) and radiation blackbody sources. We investigated a method for measuring the responsivity and noise-equivalent power (NEP) of the THz detector using two different types of light sources. When using a QCL source with a frequency of 3 THz, the average responsivity of 24 devices was $1.44{\times}10^3V/W$ and the average NEP of those devices was $3.33{\times}10^{-9}W/{\surd}Hz$. The average responsivity and NEP as measured by blackbody source were $1.79{\times}10^5V/W$ and $6.51{\times}10^{-11}W/{\surd}Hz$, respectively, with the measured values varying depending on the light source. This was because the output power of each light source was different, with the laser source being driven by a pulse type wave and the blackbody source being driven by a continuous wave. The power input to the THz sensor was also different. Futhermore, the responsivity and NEP values measured using band pass filter (BPF) were similar to those measured when using only THz windows. It was found that ACB sensor responds normally in the THz region to both the laser and the blackbody source, and the method was confirmed to effectively evaluate the characteristics of the THz sensor.