• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1543-1544
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• 2008

In this paper, we introduce a gaussian enveloped linear chirp signal that can change parameters for consideration of target material characteristics. Using the gaussian enveloped linear chirp signal, time-frequency domain reflectomety is able to detect fault location in power transmission line. we suggest design method of reference signal for power transmission line fault detection. This method is verified by locating fault in HIV low voltage power transmission line.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.3
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• pp.321-327
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• 2018

To classify seafloor sediments using a probabilistic neural network (PNN), the frequency-dependent characteristics of broadband acoustic scattering, which make it possible to qualitatively categorize seabed type, were collected from three different geographical areas in Korea. The echo data samples from three types of seafloor sediment were measured using a chirp sonar system operating over a frequency range of 20-220 kHz. The spectrum amplitudes for frequency responses of 35-75 kHz were fed into the PNN as input feature parameters. The PNN algorithm could successfully identify three seabed types: mud, mud/shell and concrete sediments. The percentage probabilities of the three seabed types being correctly classified were 86% for mud, 66% for mud/shell and 72% for concrete sediment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1549-1558
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• 2012

Location-aware system is utilized in various fields such as Logistics, Home Network, Healthcare, Military and Transportation systems. In this paper, we designed and implemented a Location-aware system based on IEEE 802.15.4a CSS (Chirp Spread Spectrum) technology in variable environment. The CSS is possible to precision location awareness using RF signal. According to experimental result, the implemented system has recognition error less than 0.5m within 20m radius in space.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.514-517
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• 2002

We developed Frequency-shifted feedback laser using AOM inside the cavity. The feedback loop of the laser is formed with the first-order diffracted light of the AOM to output mirror. It is shown that the FSF laser output has spectral output called“chirped frequency comb”with an ultrafast frequency chirp rate of several hundreds of PHz/s. It can know the range using chirped frequency comb in the optical range measurement that is FSF laser as source.

• Journal of IKEEE
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• v.16 no.4
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• pp.364-368
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• 2012

We generate 10 GHz short pulses from a continuous wave laser at 1.5 um by cascaded intensity and phase modulation, followed by chirp compensation using a single mode fiber. The measured spectral and pulse widths are 0.64 nm and 5.7 ps respectively, resulting in the time-bandwidth product of 0.46.

• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.157-158
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• 2008

High-order harmonics from gaseous atoms driven by an intense femtosecond laser pulse can form an attosecond pulse train. By selecting suitable harmonic generation conditions, the harmonic spectrum can be broad enough to form sub-hundred attoseconds. One serious limitation, however, comes from the inherent attosecond chirp originating from the harmonic generation process. We have proposed to compensate for the positive attosecond chirp by making use of negative group delay dispersion of a metallic x-ray filter or a noble gas. We generated 241-as pulses from neon and compressed them to 106 as after propagating through argon, close to the transform-limited duration of 98 as.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2714-2716
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• 2003

대역확산기술의 하나인 Chirp 방식을 이용하여 기존의 전력선 통신모뎀 보다 고속 전송이 가능한 40kbps급 협대역 전력선 통신모뎀을 구현하였다. 본 연구에서 구현한 모뎀은 CEBus 규격을 사용하였으며, $100{\sim}380kHz$의 선형 가변 주파수 신호가 25us 동안 지속한 심볼을 사용하였다. 그리고 구현된 모뎀의 무부하 선로, 각종 부하 및 잡음환경에서의 특성실험 결과, Chirp 방식의 통신기술이 협대역에서 40kbps 이상의 속도를 낼 수 있는 가능성을 확인하였다.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.484-489
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• 2002

This paper concerns the design and implementation of a Bandwidth Variable Digital Chirp Generator (DCG) for the radar altimeter. A double SRAM parallel structure is used to breakthrough the upper DCG bandwidth limited by the highest clock frequency of the digital chips. An experimental system working in the waveform storage method has been implemented. We show that the bandwidth changed according to the radar altimeter's requirement and the design released the stringent speed requirement of the chips fur making a variable wide bandwidth DCG.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.2
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• pp.195-206
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• 2022

The separation of spectrally overlapped broadband echo signals from free-swimming Japanese needlefish Hypohamphus sajori using the fractional Fourier transform (FrFT) was investigated. The broadband echo signals were measured over frequency ranges of 40-80 and 110-220 kHz. The overlapped echo signals were separated after eliminating noise signals in the smoothed pseudo-Wigner-Ville distribution domain. The echo signal from a 40 mm WC sphere suspended just below a chirp transducer was used to calibrate the broadband of the chirp echo sounder and estimate the frequency dependence of target strength for the separated echo signals. The experimental results show that the proposed FrFT method can analyze the time-frequency image of broadband echo signals from free-swimming individual fish effectively and can be used as a quantitative tool for extracting the acoustic features used for fish species identification.

• Photonics industry news
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• s.1
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• pp.63-63
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• 2000