• Title, Summary, Keyword: 주파수 변조 피드백

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Laser cooling 용 다이오드 레이저의 안정화

  • 이호성;양성훈
    • Proceedings of the Optical Society of Korea Conference
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    • pp.149-153
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    • 1995
  • 세슘원자에 대한 레이저 쿨링용 광원으로 사용하기 위해 다이오드 레이저의 서폭을 축소하고 발진 주파수 및 출력을 동시에 안정화 시키는 연구를 수행하였다. 자유발진 상태에서 약 30 MHz 이고, 출력이 10mW인 다이오드 레이저에 유이창으로 Q 갑이 낮은 외부 공진기를 구성함으로써 발진선폭을 약 5MHz로 줄일수 있었다. 그리고 세슘원자의 포화흡수 스펙트럽의 교차공진 흡수선에 레이저 주파수를 안정시키기 위해 주입전류를 10kHz 로 변조하고, lock-in amp 의 출력단에서 나오는 주파수 오차신호를 전류공급장치와 유리창이 부착된 PZT로 동시에 피드백시켰다. 또한 오차신호를 레이저 다이오드의 온도 조절장치로 피드백 시킴으로써 주파수와 동시에 레이저 출력을 안정화시킬 수 있었다. 이 때의 출력의 변동폭은 약 0.03% 로서 온도로 피드백 시키지 않는 경우에 비해 약 260배 안정된 결과를 얻었다. 그리고 컴퓨터를 이용해서 흡수선의 peak 값을 매 10초마다 검색하고 이 값이 최대가 되도록 PZT 전압을 조절함으로써 레이저 주파수를 세슘원자의 흡수선의 봉우리에 1주일 이상 안정화시킬 수 있었다. 주파수 안정도 측정을 위해 Zeeman 이동된 포화흡수 스펙트로미터를 구성하였으며, 측정된 주파수 안정도 (Allan 분산의 제곱근)는 적분시간 1초 일 때 1.2x10-10 이었다.

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A Study on Characteristics of the Stuttering according to Auditory Feedback Types (주파수 청각 피드백(FAF)에 따른 말더듬 특성 연구)

  • Chang, Hyun-Jin;Shin, Myung-Sun
    • The Journal of the Korea Contents Association
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    • v.9 no.12
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    • pp.940-947
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    • 2009
  • The study aims at investigating frequency of the stuttering of stutterers according to FAF pitch alternation level, examining a stuttering group. The study has collected spoken language samples by making each 10 people of a stuttering group carry out a reading and monologue task using NAF and FAF. The results of this study were as follows. In stuttering frequency, both reading and monologue task, there was significant difference of stuttering frequency according NAF and FAF pitch alternation level. But, There was significant difference of stuttering frequency according FAF pitch alternation level. NAF levels than FAF on type of stuttering decreased at the level of all the core behavior. The decrease was a lot of block, core behavior has changed as often repeated.

The Third-Order Multibit Sigma-Delta Modulator with Data Weighted Averaging (Data Weighted Averaging을 이용한 3차 멀티비트 Sigma-Delta 변조기)

  • 김선홍;최석우;조성익;김동용
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.41 no.9
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    • pp.107-114
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    • 2004
  • This paper presents block and timing diagrams of the DWA(Data Weighted Averaging) to optimize a feedback time delay of the sigma-delta modulator. Through the MATLAB modeling, the optimized coefficients of the integrators are obtained to design the modulator. The fully differential SC integrators, feedback DAC, 9-level quantizer, and DWA are designed by considering the nonideal characteristics of the modulator. The designed third-order multibit modulator is fabricated in a 0.35${\mu}{\textrm}{m}$ CMOS process. The modulator achieves 75dB signal-to-noise ratio and 74dB dynamic range at 1.2Vp-p 825kHz input signal and 52.8MHE sampling frequency.

A Simulation of Δ-Σ Modulators for Frequency Synthesizers of FMCW Radars (FMCW 레이더 주파수합성기용 델타-시그마 변조기의 시뮬레이션)

  • Hwang, In-Duk;Kim, Chang-Hwan
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.4
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    • pp.707-714
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    • 2012
  • After a single-stage, second-order, multiple-feedback ${\Delta}-{\Sigma}$ modulator and a two-stage, second-order MASH ${\Delta}-{\Sigma}$ modulator were analyzed and simulated using Simulink and Matlab and their characteristics were compared, the following result was obtained: 1) The two ${\Delta}-{\Sigma}$ modulators do not have group delay distortion. 2) The characteristics of the noise shaping are nearly identical. As a result of the noise shaping, the power spectral densities have slope of 40 dB/dec. 3) There was no spurious tone. 4) The input range of the two modulators is from -1 to +1 in common. 5) Because the output of the two-stage MASH modulator is 2-bits (4-levels), design of frequency dividers and charge pumps of PLL are more demanding.

Inverter Drives Adopting the Two-Phase Space Vector SRP-PWM Scheme with Fixed Switching Frequency (고정 스위칭 주파수를 갖는 2상 공간벡터 SRP-PWM기법을 적용한 인버터 구동 시스템)

  • 정영국;위석오;임영철;양승학
    • The Transactions of the Korean Institute of Power Electronics
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    • v.8 no.3
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    • pp.230-238
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    • 2003
  • In this paper, Inverter drives adopting 2 phase space vector SRP-PWM (Separately Randomized Pulse Position PWM) with fixed switching frequency is proposed. The proposed 2 phase space vector SRP-PWM scheme is based on the 3 phase SRP-PWM. In the proposed SRP-PWM scheme, each of two phase pulses is located randomly in each switching interval. The experimental results show that the voltage and acoustic noise harmonics are spread to a wide band area. Also, the performance of the proposed 2 phase SRP-PWM and the conventional center aligned SVM are compared to each other. In result, the speed response is nearly similar to each other from the viewpoint of the v/f constant control.

Analog feedback control using optical link for capacitive-coupled wireless power transmission system (광학링크를 이용한 전계결합형 무선전력전송 회로의 아날로그 피드백 제어)

  • Park, Jun-Young;Lee, Si-Ho;Hwang, Jae-Young;Choi, Sung-Jin
    • Proceedings of the KIPE Conference
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    • pp.3-4
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    • 2014
  • 무선전력전송 회로는 부하의 변동에 따라 출력값을 알맞게 제어해 줄 필요가 있는데 송신부와 수신부 회로는 분리되어 있으므로 제어루프 또한 분리되어야 한다. 기존에는 주로 통신방식이나 부하측 변조를 이용한 1차측 제어를 사용하였다. 하지만 통신을 이용하는 경우 가격이 비싸고 시스템이 복잡하며, 부하측 변조 방식은 제어회로의 반응이 느리다는 단점이 있다. 본 논문은 2.5W급 전계결합형 무선전력회로에 대하여 LED 광학링크를 이용해 송신부의 스위칭 주파수를 제어하는 회로를 제안한다. 이 회로는 수신부에 포토다이오드와 연산증폭기를 내장하여 부하에 추가적인 배터리전원 없이 저가로 우수한 성능의 제어기를 구성할 수 있으며, 그 성능을 하드웨어로 검증하였다.

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Sigma-Delta Modulator using a novel FDPA(Feedback Delay Path Addition) Technique (새로운 FDPA 기법을 사용한 시그마-델타 변조기)

  • Jung, Eui-Hoon;Kim, Jae-Bung;Cho, Seong-Ik
    • Journal of IKEEE
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    • v.17 no.4
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    • pp.511-516
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    • 2013
  • This paper presents a SDM using the FDPA technique. The FDPA technique is the added feedback path which is the delayed path of DAC output. The designed SDM increases the SNR by adding the delayed digital feedback path. The proposed SDM is easily implemented by eliminating the analog feedback path. Through the MATLAB modeling, the optimized coefficients are obtained to design the SDM. The designed SDM has a power consumption of $220{\mu}W$ and SNR(signal to noise ratio) of 81dB at the signal-bandwidth of 20KHz and sampling frequency of 2.56MHz. The SDM is designed using the $0.18{\mu}m$ standard CMOS process.

Adaptive Bit-Interleaved Coded OFDM over Time-Varying Channels (시변 채널에서 Bit-Interleaved Coded OFDM을 위한 적응 변조 기법)

  • Choi, Jin-Soo;Sung, Chang-Kyung;Moon, Sung-Hyun;Lee, In-Kyu
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.1
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    • pp.32-39
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    • 2009
  • When adapting the transmitter to the channel state information(CSI), improved transmission is possible compared to the open loop system where no CSI is provided at the transmitter. However, since the perfect channel information is rarely available at the transmitter, the system design based on the partial CSI becomes an important factor. Especially, in mobile environments, the consideration for the outdated CSI should be applied for mitigating the performance degradation. In this paper, we propose a robust adaptive modulation and coding scheme for bit-interleaved coded orthogonal frequency division multiplexing over time-varying channels. With reasonable feedback overhead, the proposed scheme shows the enhanced performance by compensating for the outdated CSI due to Doppler spread. Simulation results confirm that the performance gain is achieved by applying an accurate BER estimation method.

3rd SDM with FDPA Technique to Improve the Input Range (입력 범위를 개선한 FDPA 방식의 3차 시그마-델타 변조기)

  • Kwon, Ik-Jun;Kim, Jae-Bung;Cho, Seong-Ik
    • Journal of IKEEE
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    • v.18 no.2
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    • pp.192-197
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    • 2014
  • In this paper, $3^{rd}$ SDM with FDPA(Feedback Delay Pass Addition) technique to improve the input range is proposed. Conventional architecture with $3^{rd}$ transfer function is just made as adding a digital delay path in $2^{nd}$ SDM architecture. But the input range is very small because feedback path into the first integrator is increased. But, proposed architecture change feedback path into the first integrator to the second integrator, so input range could be improved about 9dB. The $3^{rd}$ SC SDM with only one operational amplifier was implemented using double-sampling technique. Simulation results for the proposed SDM designed in $0.18{\mu}m$ CMOS technology with power supply voltage 1.8V, signal bandwidth 20KHz and audible sampling frequency 2.8224MHz show SNR(Signal to Noise Ratio) of 83.8dB, the power consumption of $700{\mu}W$ and Dynamic Range of 82.8dB.