• Journal of Forest and Environmental Science
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• 제32권1호
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• pp.99-102
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• 2016

Echolocation call structure and intensity were measured from the Malaysian Myotis muricola, which were recorded from the hand-released bat. The Malaysian M. muricola produced typical FM call pattern of the genus Myotis, producing steep, downward frequency-modulated calls. The average PF of calls is $64.39{\pm}1.33(kHz)$. Discrete PF patterns of two types are found, which consist of 63.39 kHz and 66.15 kHz. The averages of SF and D are $126.07{\pm}3.37kHz$ and $2.14{\pm}0.29ms$, respectively. There are various IPI lengths with average of $42.97{\pm}12.68ms$. A pulse consists of two harmonies which consist of the first harmony with wider bandwidth and the second harmony with narrower bandwidth. The PF of the first harmony is higher than that of the second harmony. The typical FM call structure, with two harmonies and wide bandwidth, would be highly related to fast flying and wide screening in the dense forests.

• Journal of Forest and Environmental Science
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• 제32권1호
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• pp.68-73
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• 2016

We investigated structure and intensity of 267 echolocation calls that were collected from the five Korean Myotis species (M. nettereri, M. petax, M. ikonnikovi, M. macrodactylus and M. formosus). All the Myotis species produced typical FM call pattern with similar echolocation call shapes and outer shapes, producing steep, downward frequency-modulated calls. A pulse has two harmonies, which consist of the first harmony with wider bandwidth and the second harmony with narrower bandwidth. The PF of the first harmony is higher than that of the second harmony. The typical FM call structure, with two harmonies and wide bandwidth, might be highly related to fast flying and wide screening in the dense forests. In classification of the echolocation calls by DFA, most of calls from the five species could be well correctly classified. All calls of M. nettereri (100% of 17 calls), M. formosus (95.5% of 22 calls) and M. ikonnikovi (85.7% of 70 calls) could be well discriminated from those of the other species, whereas calls of M. petax and M. macrodactylus could be discriminated by 70.4% of 98 calls and 76.7% of 60 calls, respectively. Our results indicate that the five Korean Myotis species can be well identified by the echolocation calls with high correct classification by DFA.

• 한국ITS학회 논문지
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• 제4권1호
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• pp.89-95
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• 2005

본 논문에서는 GSM/GPS/DCS/US-PCS 핸드 셋을 위한 4중 대역 안테나를 제안한다. 제안되어진 안테나는 핸드 셋의 제한된 내부 공간에 집적하기 위하여 저자세로 설계되어 지고 ,다중대역을 위해 $\lambda$/4 길이를 갖는 세 개의 방사점으로 구성된다. 또한 안테나의 크기 변화 없이 넓은 대역폭을 얻기 위하여 방사체 아래의 접지면을 제거하였고, GPS/DCS/US-PCS 대역의 편리한 임피던스 매칭을 위하여 방사체 중앙에 슬릿을 추가하였다. 제안되어진 안테나는 전 대역에서 VSWR 3:1 대역폭을 만족하고, anechoic chamber (10m$\times$6m$\times$4m)내의 측정 결과 전 대역에서 최대 이득은 -2.19 dB 에서 2.09 dB이다

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 춘계학술대회
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• pp.61-62
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• 2017

본 연구에서는 주파수 1.5GHz~1.7GHz 넓은 대역에서 동작하는 내부 슬롯과 외부 스터브를 갖는 원형편파 패치 안테나를 설계하였다. 광대역 특성과 고 이득을 갖기 위해 기본적으로 접지판으로부터 높은 공기층을 적용하였다. 임피던스 대역폭을 개선하기 위하여 패치의 크기, 매인 패치와 접지판 간거리, 내부 슬롯의 길이, 급전 위치, 외부 스터브의 길이 등을 조정하였다. 시뮬레이션을 통해 1.5GHz~1.7GHz 대역의 안테나를 설계하고 반사손실, 이득, 방사패턴 등의 안테나 특성을 확인하였다.

• ETRI Journal
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• 제41권2호
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• pp.167-175
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• 2019

A wideband dual-polarized antenna coupling cross resonator is proposed for LTE700/GSM850/GSM900 base stations. An additional resonance is introduced to obtain strong coupling between the dipole and resonator. Moreover, the input impedance of the proposed antenna is steadily close to $50{\Omega}$, which results in better impedance matching. Therefore, a wide bandwidth can be achieved with multiresonance. A prototype is fabricated to verify the proposed design. The measured results show that the antenna has a fractional bandwidth of 35.7% from 690 MHz to 990 MHz for ${\mid}S_{11}{\mid}$ < -15 dB. Stable radiation patterns as well as gain are also obtained over the entire operating band. Moreover, a five-element antenna array with an electrical downtilt of $0^{\circ}$to $14^{\circ}$ is developed for modern base station applications. Measurement shows that a wide impedance bandwidth of 34.7% (690 MHz to 980 MHz), stable HPBW (3-dB beamwidth) of $65{\pm}5^{\circ}$, and high gain of $13.8{\pm}0.6dBi$ are achieved with electrical downtilts of $0^{\circ}$, $7^{\circ}$, and $14^{\circ}$.

• 한국전자파학회논문지
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• 제24권6호
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• pp.581-585
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• 2013

마이크로스트립 패치 안테나의 대역폭을 확장하기 위한 방안을 제시하였다. 이 안테나는 사각형의 슬롯을 가진 접지판 위에 변형된 T-자 모양의 마이크로스트립 라인으로 급전되는 구조를 갖는다. 제시된 마이크로스트 립 패치 안테나는 슬롯과 변형된 T-자 모양의 급전 라인의 크기와 위치를 최적화시킴으로써 광대역 특성을 구현 하였다. 컴퓨터 모의실험 결과에 의하면 VSWR 2:1 기준에서 127.8 %(0.65~2.95 GHz)의 대역폭을 얻을 수 있었다.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권3호
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• pp.180-185
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• 2005

Microstrip antennas generally have a lot of advantages that are thin profile, lightweight, low cost, and conformability to a shaped surface application with integrated circuitry. In addition to military applications, they have become attractive candidates in a variety of commercial applications such as mobile satellite communications, the direct broadcast system (DBS), global positioning system (GPS), and remote sensing. Recently, many of the researches have been achieved for improving the impedance bandwidth of microstrip antennas. The basic form of the microstrip antenna, consisting of a conducting patch printed on a grounded substrate, has an impedance bandwidth of $1\~2\%$. For improvement of narrow bandwidth of microstrip patch, we were designed U-slot microstrip patch antenna in this paper. This antenna had wide bandwidth for all personal communication services (PCS) and IMT-2000. For the design of U-slot microstrip patch antenna using a finite difference time domain(FDTD) method. This numerical method could get the frequency property of U-slot patch antenna and the electromagnetic fields of slots.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2018년도 추계학술대회
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• pp.431-433
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• 2018

본 논문은 광대역 음성의 음질 향상을 위해 시간 영역에서 인공대역 확장 기술을 사용하여 초광대역 음성신호를 출력하여 사용자에게 개선된 음질의 음성을 제공하는 시스템을 제안한다. 시간 영역에서 소스필터 모델에 기반하여 광대역 여기신호 및 LSP를 추출하고, 각각의 대역폭 확장 알고리즘을 적용였고, 초광대역 여기신호 및 LSP를 추론하여 초광대역 음성신호를 합성한다. 주관적인 테스트를 통해 광대역 음성신호보다 초광대역 음성신호의 음질을 더 선호하는 결과를 도출하였다.

• Journal of the Optical Society of Korea
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• 제18권1호
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• pp.15-22
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• 2014

We present a novel bandwidth measurement scheme for multimode optical fibers. Amplified spontaneous emission (ASE) radiation was utilized for a source of intrinsically modulated light with a wide modulation bandwidth. In our measurement scheme, the continuous-wave (CW) ASE light that passed through a multimode fiber (MMF) under test was analyzed by the fourth-order power with a high-speed photodetector and an electric spectrum analyzer. The modulation transfer function of the multimode fiber could be directly measured with the photoelectric spectra in the modulation frequency domain. The measurement result of our method was experimentally compared to that of the conventional measurement scheme based on the impulse response measurement. It has been found that our scheme provides a stable measurement means of MMF characterization that is suitable for the field testing due to the simplicity of the system.

• ETRI Journal
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• 제26권1호
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• pp.57-60
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• 2004

We propose an inductive compensation method for a surface-mountable 10 Gbps photoreceiver module. Since many typical 10 Gbps photoreceiver modules consist of a photodetector and low-noise pre-amplifier, the impedance mismatch between the photodetector and pre-amplifier, as well as package parasitics, may reduce the frequency bandwidth. In this paper, we inserted an inductive component between the photodetector and pre-amplifier in order to create frequency bandwidth expansion. From the measurement results, we have found that the proposed technique can increase the -3 dB bandwidth about 4.2 GHz wider compared with an uncompensated module. And, from a bit-error rate (BER) test, we observed -15.7 dB sensitivity at $10^{-12}$ BER. This inductive compensation can be implemented easily and is compatible with common manufacturing processes of photoreceiver modules.