• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.107-113
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• 2016

In this paper, we suggest a design method of a wide-band Butler matrix working at 5.9 GHz for V2X communication antennas. Since V2X communication needs beam-forming and beam-steering antennas to make transportation systems, mobile comm platforms, saturated frequency-resources, and signal TX-and-RX smart, multi-functional, resolved, and efficient utmost, respectively, the proper Butler matrix and its radiating elements as a low-profile geometry are realized. The constitutive components of the basic Butler matrix of a narrow band are designed first. And then, it is extended to a wide-band version to make its frequency-shift less affected by the event of the antenna system being mounted on a car body. The beam-forming and beam-steering performance is presented as the common feature tagged along with the different bandwidths of the frequency responses as the comparison between the narrow- and wide-band cases.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.422-429
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• 2008

This paper presents compact low frequency ultra-wide band (UWB) sensor design and study of the partial discharge diagnosis by sensing electromagnetic pulse emitted from the partial discharge source with the newly designed UWB sensor. In this study, we designed a new type of compact low frequency UWB sensor based on microstrip antenna technology to detect both the low frequency and high frequency band of the partial discharge signal. Experiments of offline PD testing on medium voltage (22.9kV) underground cable mention the comparative results with the traditional HFCT as a reference sensor in the laboratory. In the series of comparative tests, the calibration signal injection test provided with the conventional IEC 60270 method and high voltage injection testing are included.

• Journal of the Korea Society of Computer and Information
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• v.16 no.10
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• pp.131-136
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• 2011

In this paper, we fabricate multi channel receiver for radar system. This receiver at X-band can be received 8 signal of an identical characteristic, dynamic range has more than 80[dB]. To process direct received signals, this system has the built-in two digital de-modulators which offer the minimum loss on the receiving signal path and has high stability by adding Built-In Test. The gain, noise figure, difference of amplitude and phase on the signal path is respectively 20${\pm}$2[dB], 19[dB], ${\pm}$2[dB], $10^{\circ}$ and below.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.1
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• pp.53-60
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• 2010

This paper dealt with the acoustic detection of partial discharge (PD) in insulation oil for insulation diagnostics of oil immersed transformers. Electrode systems such as needle to plane, plane to plane, and floating were fabricated to simulate some defects in transformers. A wide band acoustic emission(AE) sensor with the frequency ranges of 100 kHz~1 MHz and a narrow band AE sensor with the resonant frequency of 140 kHz were used in the experiment. Also, a decoupler and an amplifier were designed to detect and amplify the acoustic signal only. The decoupler separates acoustic signal from DC source without any distortion, and the amplifier has the gain of 40 dB in frequency ranges of 11 kHz~4 MHz. In the experiment, frequency components and propagation characteristics of acoustic signal were analyzed, and an algorithm of positioning of PD occurrence by the time difference of arrival was proposed. From the results, the frequency components of the acoustic signal exist from 50 kHz to 200 kHz and the positioning error of PD calculated by three AE sensors was within 1%.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.143-144
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• 2017

다양한 응용 매체의 유비쿼터스(ubiquitous) 연결을 위한 사물 인터넷 (Internet-of-Thing; IoT) 시스템은 저전력 광역 통신 (Low Power Wide Area; LPWA) 기술을 기반으로 한다. 저전력 광역 통신 시스템의 충족조건인 전송 거리 확대와 낮은 전력 사용은 시스템 전력 운용 관점에서는 상호 충돌하는 조건이다. 이를 위해 신호대역폭을 줄여 수신기 감도 (receiver sensitivity) 를 개선하는 초협대역 (Ultra Narrow Band; UNB) 기술이 주목받고 있다. 여기서는 이러한 저전력 광역 통신을 위한 초협대역 변조 기술의 신호 대 잡음 비(Signal-to-Noise Ratio; SNR)에 대해 분석한다.

• Journal of Magnetics
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• v.18 no.2
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• pp.178-182
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• 2013

We have developed a new non-conventional electron paramagnetic resonance (EPR) spectrometer, in which no resonant cavity was used. We previously demonstrated a wide frequency range operation of an EPR spectrometer using two loop antennas, one for a microwave transmission and the other for signal detection [1]. In contrast to Ref. [1], the utilization of a microstrip antenna as a transmitter enhanced a capability of wide-band operation. The replacement of conventional capacitors with varactor diodes makes resonance condition easily reproducible without any mechanical action during tuning and matching procedure since the capacitance of the diodes is controlled electronically. The operation of the new EPR spectrometer was tested by measuring a signal of 1,1-diphenil-2-picrylhydrazyl (DPPH) sample in the frequency range of 0.8-2.5 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1071-1077
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• 2010

The six-port phase correlator using lumped elements was designed and fabricated in this paper, also the receiving performance of L-band direct conversion receiver using lumped six-port phase correlator element was analyzed. The proposed L-band lumped six-port phase correlator element was composed of a resistive power divider and the twist-wire coaxial cables. The proposed lumped six-port structure provides the small-sized configuration and wide-band characteristics. The performance of the L-band lumped direct conversion receiver structure was measured under the conditions of 1.69 GHz frequency for LO-CW signal and RF-QPSK signal, which are input signals for the lumped six-port phase correlator element. The direct conversion receiving structure using the proposed lumped six-port phase correlator element can recovered the good digital I/Q signal.

• Journal of the Korean Institute of Telematics and Electronics
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• v.8 no.3
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• pp.27-32
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• 1971

This paper presents the analysis of the amplitude distortion occurring in the transmission of super wideband AM signal when the amplitude and phase variations of the upper and lower sidebands of the AM signal are symmetrical, and odd symmetrical with respect to the carrier. It is shown that the case where the amplitude variations of the upper and lower sidebands of AM signal are symmetrical with respect to the carrier while the phase variations of the upper and lower sidebands are odd symmetrical with respect to the carrier induce, no amplitude distortion in AM signal transmission.

• Publications of The Korean Astronomical Society
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• v.18 no.1
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• pp.51-60
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• 2003

This paper is the research and development including the system design and the prototype system building of the 400MHz wide-band digital autocorrelation spectrometer system for radio astronomy observation, which will be used as back-end signal processing unit of the Dual channel SIS receiver at Taeduk Radio Astronomy Observatory. So in this paper, we performed development of the high speed digitizing sampler, the circular memory buffer, and the correlator module for the 400MHz wide-band digital autocorrelator. This developed system will be use at TRAO after the housing and some calibration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.68-73
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• 2002

This paper presents the implementation of wide-band RFIC amplifier operating from near 50 MHz to 3 GHz using Tachyonics SiGe HBT foundry. Voltage shunt feedback is used for the flat gain and the broad band impedance matching. Initial design parameters are calculated through the low frequency small signal analysis. Since the HBT model was not available at the design time, discrete tuning board was made for fine adjustment in the low frequency range. Fabricated amplifier shows 12 dB gain with 1 dB fluctuation and P1 dB reaches 15 dBm at 850 MHz.