• 한국광학회지
• /
• 제5권2호
• /
• pp.291-297
• /
• 1994

Erbium첨가 광섬유 증폭기에서 증폭된 자연방출광(ASE) 출력의 일부를 대역투과 파장 필터를 거쳐 입력단으로 루프 귀환시켜 광증폭기를 특정 파장에서 발진시킴으로써 신호광에 대한 증폭 이득을 일정치에 고정시켰다. 증폭 이득과 ASE 출력 스펙트럼은 광증폭기가 발진하는한 입력광 power나 펌프광 power의 변화에 대하여 무관하였으며 귀환 루프의 손실에만 의존하였다. 또한 광증폭기에 저속으로 변조된 대신호가 입사하는 경우에도 이득포화에 의한 파형 왜곡없이 증폭이 가능하였다.

• 한국통신학회논문지
• /
• 제21권7호
• /
• pp.1833-1841
• /
• 1996

Recently, by emerging of the ALE techniques that make it possible to providereliable communications link automatically, high frequency communiation is newly used as emergency communication and back-up for satellite communications. ALE signal is transmitted in burst, and the received signal is subject to distortions by detrimental multipath fading channels. In the case of that channel, the performance of ALE system is highly dependent upon that of synchronization techniques. In this paper, M-ary FSK signals are detected by a bank of bandpass filter, which is implemented using recusive DFT(Discrete Fourier Transform). Also an acquisition and trancking algorithm are designed uisng parallel structure and early-late-gate methods respectively. Finally, we verify the performance ofthe proposed synchronization algorithm by the computer simulation.

• Structural Engineering and Mechanics
• /
• 제39권6호
• /
• pp.813-831
• /
• 2011

This paper presents an efficient version of Hilbert-Huang transform for nonlinear non-stationary systems analyses. An ensemble empirical mode decomposition (EEMD) is introduced to alleviate the problem of mode mixing between intrinsic mode functions (IMFs) decomposed by EMD. Yet the problem has not been fully resolved when a signal of a similar scale resides in different IMF components. Instead of using a trial and error method to select the "best" outcome generated by EEMD, a hybrid algorithm based on EEMD and EMD is proposed for multi-mode signal processing. The developed approach comprises the steps from a bandpass filter design for regrouping modes of the IMFs obtained from EEMD, to the mode extraction using EMD, and to the assessment of each mode in the marginal spectrum. A simulated two-mode signal is tested to demonstrate the efficiency and robustness of the approach, showing average relative errors all equal to 1.46% for various noise levels added to the signal. The developed approach is also applied to a real bridge structure, showing more reliable results than the pure EMD. Discussions on the mode determination are offered to explain the connection between modegrouping form on the one hand, and mode-grouping performance on the other.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
• /
• pp.413-416
• /
• 2001

In high frequency range, RF circuit design without considering shielding effect can cause several significant changes due to increase in parasitic capacitance and inductance between RF signal lines and shielding box. In this paper, bandpass filter has been made to measure the shielding effect and its s-parameter has been measured by Vector Network Analyzer (VNA). Equivalent circuit model including the shielding effect has been constructed with the lumped elements extracted from the 3D electromagnetic simulator, Maxwell SI. Then, the validity of the model is verified using microwave circuit simulator, ADS (Advanced Design System).

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1994년도 추계학술대회 논문집
• /
• pp.360-364
• /
• 1994

This paper is concerned with extracting the diagnostic signature for motor-operated valves (MOV's) noninvasively. A torque estimator is developed and tested to obtain electical torque of the induction motors which are attached to the MOV's. Inverse filter is used to recover the gear meshing forces from the measured actuator housing vibration, which contain the gear rotation information. Frequency demodulation techniques are performed and an adaptive linear bandpass filter is implemented to improve signal-to-noise ratio. Finally, stand-alone valve experiments are carried out to validate the signature extraction scheme.

• Journal of the Optical Society of Korea
• /
• 제19권3호
• /
• pp.255-259
• /
• 2015

We have proposed and experimentally verified a pulse-width modulation (PWM) generator which directly generated a PWM signal in the optical domain. Output waveforms were clear at the repetition rate of 16 MHz; the duty cycle (DC) was from 14.7% to 72.1%; and the DC-control resolution was about 4.399%/dB. The PWM generator' operation principle is based on the injection-locking property of a single-mode Fabry-$P{\acute{e}}rot$ laser diode (SMFP-LD). The SMFP-LD, which has a self-locked mode wavelength at ${\lambda}_{PWM}$, was used to detect the power of the injection-locking signal (optical analog input). If the analog input power is high, the SMFP-LD is locked to the wavelength of the input signal ${\lambda}_a$ and there is no output after an optical bandpass filter (OBF). If the analog input power is low, the SMFP-LD is unlocked and there is output signal at ${\lambda}_{PWM}$ after the OBF. Thus, the SMFP-LD plus the OBF provide digital output for an analog input. The DC of the output PWM signal can be controlled by tuning the power of the analog input.

• 대한전자공학회논문지TC
• /
• 제48권1호
• /
• pp.92-96
• /
• 2011

본 논문에서는 CRLH 구조의 대역통과여파기를 이용하여 선형성이 개선된 전력증폭기를 구현하였다. CRLH 구조를 이용한 대역통과여파기외 구조는 윗변에는 인터디지트 형태의 신호선으로, 아랫면에는 CSRR 형태의 구조로 이루어져 있으며 via를 통해 윗면과 아랫면이 연결되어 있다. 전력증폭기의 동작대역에서 손실을 최소화하고 CRLH 전송 선로를 이용하여 2차 고조파 성분을 제한시켜서 전력증폭기의 선형성을 개선하였다. 2.l4GHz에서 동작하는 전력증폭기의 측정된 출력 전력은 33dBm 기준으로 2차 고조파는 -53.527 dBc, 3차 혼변조 신호는 -36.16 dBc, 부가전력효율은 33.14% 가 측정되었으며, 이는 기존의 전력증폭기에 비해 2차 고조파는 약 16 dB, 3차 혼변조 신호는 약 12 dB 개선되었다.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2005년도 추계종합학술대회
• /
• pp.131-134
• /
• 2005

Recently, RF systems have rapidly grown with the extension of the mobile communication service The mobile service companies are providing the satellite broadcasting and common usage are expected. Coinciding with current trend, the development of improved satellite DMB (Digital Multimedia Broadcasting) tuner is required. To improve the receiving sensitivity under the poor communication circumstance, It is necessary to design the LNA (Low Noise Amplifier) with outstanding low noise characteristic and the BPF (Bandpass Filter) to transmit only desired signal without distortion and loss. Besides high reliability, the miniaturization and lightweight are required for design of mobile terminals. In this study, we designed and fabricated DMB SIR-type BPF which operates at 2642 MHz and is embedded in the substrate using LTCC. As a result, we obtained the passband insertion loss of 2.4 dB and the passband ripple of 0.08 dB. So this DMB SIR-type BPF is applicable to RF module of a satellite DMB tuner.

• 전기전자학회논문지
• /
• 제10권2호통권19호
• /
• pp.109-115
• /
• 2006

본 논문에서는 FCC 규격을 만족하는 DS-UWB 통신을 위한 고차미분 가우시안 펄스 생성기를 제안하고, 이를 실험적으로 구현하였다. 100Mbps의 구형파를 가우시안 펄스로 변환하기 위해 두개의 SRB만을 이용한 가우시안 펄스 발생기를 제작하였다. 출력된 펄스는 330 psec의 펄스폭과 920 mV의 크기를 가진다. 또한 WLAN 대역을 제거하기 위해 마이크로스트립 라인과 병렬 스터브를 이용한 고차미분의 특성을 가지는 이중 대역통과 필터를 설계 및 제작하였다. 최종적으로 WLAN 대역을 -25dB 이상 억제를 하고, 시간축 상에서 1 nsec의 펄스폭과 25 mV의 크기를 가지는 13차 가우시안 펄스를 출력하였다.

• 한국컴퓨터정보학회논문지
• /
• 제7권2호
• /
• pp.130-135
• /
• 2002

본 논문에서는 구조적인 장점 때문에 최근 초고주파 소자에 많이 사용되고 있는 코플러너 웨이브가이드를 사용하여 대역통과 필터를 이동통신 기지국용 모듈형태로 설계.제작하였다. Itoh의 Conductor-Backed Coplanar Waveguide를 이용하였으며. 각 단의 임피던스를 실제로 제작이 가능한 잎피던스 값을 갖도록 파라미터 H를 2.4로 선택하여 계산하였다. 선로의 길이는 $\lambda$/4인 코멘슈레이트 선로를 사용하였으며, 접지면 사이의 간격을 고정하고 신호선의 폭을 구하였다. 설계된 필터는 마이크로스트립 필터보다 적은 공간을 차지하면서 예리한 차단특성과 통과대역 전 대역의 return loss가 15dB인 우수한 특성을 얻을 수 있었다.