• Journal of information and communication convergence engineering
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• 제9권3호
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• pp.305-309
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• 2011

This paper proposes a new rotational frequency detector (RFD) for phase-locked loop (PLL) or clock and data recovery (CDR) applications for fast frequency acquisition. The proposed RFD uses the four states finite state machine (FSM) model to accelerate the frequency acquisition time. It is modeled and simulated with MATLAB Simulink. The functionalities of the proposed RFD are examined and the results are compared to those of a conventional RFD. The proposed RFD's frequency acquisition time is four times faster than that of a conventional one. The proposed RFD incorporated with a phase detector (PD) in PLL or CDR is expected to improve the frequency and phase acquisition performance later greatly.

• 방송공학회논문지
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• 제15권2호
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• pp.182-191
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• 2010

본 논문에서는 DVB-S2 시스템을 위한 간단한 구조를 가지는 반송파 주파수 복구부를 소개한다. 위성방송 통신 환경 및 상용 부품의 사용으로 인해, DVB-S2 수신기의 반송파 주파수 복구부는 최대 20%의 정규화된 주파수 옵셋(Offset)을 복구해야만 한다. 이로 인해 기존에 소개된 반송파 주파수 복구 방식은 복잡한 구조를 가지고 많은 연산량 및 메모리를 필요로 한다. 본 논문에서 소개된 방식은 거친 주파수 복구부에 변형된 Fitz 방식을 채택하여 정확하게 거친 주파수 옵셋 복구를 수행하고, 잔류 주파수 옵셋을 후단의 알려진 간단한 미세 주파수 복구방식으로 처리하는 구조를 갖는다. 소개된 방식은 기존에 소개된 방식과 동일한 성능을 보이면서도 필요한 곱셈 연산량을 80% 가량 줄일 수 있고 추가적인 메모리를 필요로 하지 않는 장점이 있다.

• 대한임상전기생리학회지
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• 제8권1호
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• pp.1-5
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• 2010

Purpose : This research inquires into the effect of applying microcurrent (MC) according to various frequency levels on the pain and functional recovery of patients with chronic back pain. Methods : Thirty participants with chronic lower back pain disease were divided equally into three experimenta l groups. The MC frequency used in the first experimental group was 0.5Hz, the second experimental group was 50Hz, and the third experimental group was 100Hz for 20 minute sessions. A hot pack and ultrasound were applied to all groups as the general physical therapy. Measurements were taken using the visual analogue scale (VAS), the face pain rating scale (FPRS), and the Oswestry disability index (001). The analysis used the paired t-test in order to compare pretest and posttest results. A one-way ANOVA was performed to make comparisons with regards to frequency levels. Results : VAS, FPRS, and 001 showed significant pain decrease in all groups except for the 001 measurement in the 0.5 Hz group. There were no significant differences according to frequency levels. Conclusion: For chronic pain and functional recovery, a microcurrent produces an effect after treatment. However, results did not show a significant difference in change obtained from differing frequency levels.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.191-196
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• 2005

A low-cost, high-performance 40 Gb/s clock recovery module using a phase-locked loop(PLL) for a 40 Gb/s optical receiver has been designed and implemented. It consists of a clock recovery circuit, a RF mixer and frequency discriminator for phase/frequency detection, a DR-VCO, a phase shifter, and a hold circuit. The recovered 40 GHz clock is synchronized with a stable 10 GHz DR-VCO. The clock stability and jitter characteristics of the implemented PLL-based clock recovery module has shown to significantly improve the performance of the conventional open-loop type clock recovery module with DR filter. The measured peak-to-peak RMS jitter is about 230 fs. When input signal is dropped, the 40 GHz clock is generated continuously by hold circuit. The implemented clock recovery module can be used as a low-cost and high-performance receiver module for 40 Gb/s commercial optical network.

• 전기학회논문지
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• 제61권2호
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• pp.324-328
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• 2012

A recovered jitter of CDR(Clock and Data Recovery) Circuit based on Dual-loop DLL(Delay Locked Loop) for data recovery in high speed serial data communication is changed by depending on the input data and reference clock frequency. In this paper, 2-step DPC which has constant jitter performance for wide-range input frequency is proposed. The designed prototype 2-step CDR using proposed 2-step DPC has operation frequency between 200Mbps and 4Gbps. Average delay step of 2-step DPC is 10ps. Designed CDR circuit was tested with 0.18um CMOS process.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.403-406
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• 2003

In this paper, we have proposed a carrier recovery algorithm of OFDM/QPSK-DMR(Orthogonal Frequency Division Multiplexing/Quadrature Phase Shift Keying Modulation-Digital Microwave Radio)system using BL-PSF(Band Limited-Pulse Shaping Filter) and have analyzed the carrier phase MSE(Mean Square Error) performance of OFDM/QPSK and single carrier DMR systems. The existing OFDM/QPSK-DMR system using windowing requires training sequence or CP(Cyclic prefix) to synchronize a receive. carrier frequency. Because in the OFDM/QPSK-DMR system using BL-PSF there is no training sequence or CP(Cyclic Prefix), we also propose a carrier recovery useful to the system. The simulation results confirm that the proposed carrier recovery algorithm has the same carrier phase MSE(Mean Square Error) performance for the single carrier DMR system under AWGN(Additive White Gaussian Noise) environment.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.394-397
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• 2003

In this paper, we have proposed a clock recovery algorithm of OFDM/QPSK-DMR(Orthogonal Frequency Division Multiplexing/Quadrature Phase Shift Keying Modulation-Digital Microwave Radio)system using BL-PSF(Band Limited-Pulse Shaping Filter) and have analyzed the clock phase error variance performance of OFDM/QPSK and single carrier DMR systems. The existing OFDM/QPSK-DMR system using the windowing requires training sequence or CP(Cyclic Prefix) to synchronize a receiver clock frequency Because there is no training sequence or CP(Cyclic prefix) in our proposed DMR system, the proposed clock recovery algorithm is useful to the OFDM/QPSK-DMR system using BL-PSF, The simulation results confirm that the proposed clock recovery algorithm has the same clock phase error variance performance in a single carrier DMR system under AWGN(Additive White Gaussian Noise) environment.

• 한국통신학회논문지
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• 제38A권7호
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• pp.545-551
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• 2013

MQASK 수신기에서 수신 심볼의 타이밍 동기에 사용되는 타이밍 복원 루프 Timing Error Detector(TED) 와 입력신호의 표본화율을 제어하는 VCO또는 NCO 및 루프 필터로 구성된다. 여기서 수신신호의 심볼율과 수신기의 표본화율의 시간 축에서의 위상차를 검출하는 TED는 심볼율과 표본화율의 주파수차가 클 경우 정상동작을 하지 못하는 단점이 있다. 본 논문에서는 PLL의 주파수 검출기와 같은 역할을 타이밍 복원 루프에서 수행하여 타이밍 복원 입력 신호의 주파수 차가 매우 큰 경우에도 타이밍 복원을 가능하게 할 수 있는 심볼율 변별기(Symbol Rate Discriminator SRD) 와 이를 사용한 타이밍 복원루프 구조를 제안 하였으며 이를 통해 심볼율이 가변되는 신호에 대한 타이밍 동기 획득이 가능함을 모의실험을 통해 입증하였다.

• 대한의용생체공학회:의공학회지
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• 제40권2호
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• pp.68-74
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• 2019

Lateral epicondylitis is caused by repeated use of the wrist, which causes inflammation and pain in the wrist extensor and tendon of the humerus. Delayed onset muscle soreness (DOMS) caused by repetitive resistance exercise affects the tendons connected in series with the muscle, leading to lateral epicondylitis. Although micro-current stimulation has been suggested as a possible treatment for tendinitis, there are insufficient studies on specific variables such as frequency. In this study, 15 healthy adult males and females developed DOMS in the wrist extensor and tendon in the humerus. The experimental group consisted of a low frequency group applying 20 Hz and a high frequency group applying 100 Hz according to the micro-current frequency. Each subject underwent an experiment for 5 days after DOMS, and the recovery rates were compared by measuring AROM, GPT, MST, PPT, and VAS. As a result, the 20 Hz group showed significant changes in AROM, MST, and VAS compared to the control group on the 4th day, and the recovery rate was also higher than that of the 100 Hz group. On the 5th day, recovery rate of 100 Hz group was higher than 20 Hz in AROM and PPT, and MST showed higher recovery rate than 20 Hz group, but there was no significant difference. These results indicate that microcurrent stimulation is effective for the treatment of delayed myalgia and tendon inflammation and that the 100 Hz group has faster recovery than the 20 Hz group.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.9-11
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• 2005

Adequate Co-ordination between Generator Speed Governor and AGC plays major role in maintaining a Frequency Stability. Recently frequency instability cases were recorded when power system was unbalanced between generation and demand in Korea. The paper deals with the concept of Generator frequency control logic & AGC algorithm for determining generator output target. Consequently the paper presents the improvement of EMS AGC control for stable frequency recovery in case of generator disturbance.