• 제목/요약/키워드: Doppler Frequency

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Determination of Flow Direction by Using an Acousto-Optic Effect (광음향 변조효과를 이용한 유체의 방향 결정)

  • 김규욱
    • Proceedings of the Optical Society of Korea Conference
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    • 1990.02a
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    • pp.34-36
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    • 1990
  • The flow direction in a glass tube is measured by using a forward scatering dual beam laser Doppler velocimeter with an acousto-optic modulator. We can determine the flow direction by measuring the shifted Doppler frequency which is dependent on the order of modulation of the laser frequency shifting moves only the Doppler signal, enabling complete separation of the Pedestal and Doppler singal.

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A Study on Measurement of Heartrate and Respiration during Sleep using Doppler Radar: Preliminary Study (도플러 레이더를 이용한 수면 중의 심박 및 호흡 측정: 예비연구)

  • Lim, Yong Gyu
    • Journal of Biomedical Engineering Research
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    • v.38 no.5
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    • pp.264-270
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    • 2017
  • A Doppler radar sensor was applied to detect respirations and heartbeats of persons who were lying on a bed. This study is preliminary study aiming at non-contact and non-intrusive respiration and heart rate monitoring during sleep in daily life. For the experiments, 10GHz Doppler radar with patch-type antenna was used and installed on the upper right and the distance between the body and the antenna was 1 m. The results show that each signal of respiration and heartbeat is observed in each frequency band however the frequency band and the waveform vary according to the subjects and the posture. The results show that the heartbeats can be detected with the peak detection in some frequency band. This study shows the feasibility of applying the Doppler radar to detection of heartbeat and respiration during sleep and further studies about heartbeat detection algorithm are required.

Laser doppler velocimetry using the optogalvanic effect of $Co_2$ laser (광전류 효과를 이용한 $Co_2$ 레이저 도플러 속도 측정기)

  • 최종운;김용평;김윤명
    • Korean Journal of Optics and Photonics
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    • v.8 no.6
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    • pp.482-485
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    • 1997
  • A new laser Doppler velocimeter employing a $CO_2$laser has been developed by using its optogalvanic effect. A change in the electric impedance of a discharge, induced by mixing of a returned wave with an originally existing wave inside the cavity, was employed to detect the Doppler frequency shift. A Doppler frequency shift as much as 60 KHz was detected, and also a good linear relationship between the velocity and the Doppler frequency shift was obtained.

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GPS L5 Acquisition Schemes for Fast Code Detection and Improved Doppler Accuracy

  • Joo, In-One;Sin, Cheon-Sig;Lee, Sang-Uk;Kim, Jae-Hoon
    • ETRI Journal
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    • v.32 no.1
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    • pp.142-144
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    • 2010
  • In this letter, we propose GPS L5 acquisition schemes to detect a fast code phase and improve the accuracy of the Doppler frequency. The proposed approach is based on the code-phase changes which occur during the acquisition processing time originating in the Doppler frequency. The proposed schemes detect a fast code phase within about 1 chip near the estimated code phase and improve the accuracy of the Doppler frequency by up to about 4 times in comparison with the popular Septentrio receiver. The feasibility of the proposed schemes is demonstrated through simulation.

Photoacoustic Laser Doppler Velocimetrv Using the Self - mixing Effect of RF - excited CO2 Laser

  • Choi, Jong-Woon;You, Moon-Jong;Choi, Sung-Woong;Woo, Sam-Young
    • Journal of the Optical Society of Korea
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    • v.8 no.4
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    • pp.188-191
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    • 2004
  • A new laser Doppler velocimeter employing a $CO_2$ laser has been developed by using its photoacoustic effect. A change in the pressure of a discharge, induced by mixing of a returned wave with an originally existing wave inside the cavity, is employed to detect the Doppler frequency shift. We found that a Doppler frequency shift as small as 50 kHz was detected, and also a good linear relationship between the velocity and the Doppler frequency shift was obtained.

A Study on Estimation of Doppler Frequency in a Current Velocity Measurement Radar (유속 측정 레이다에서의 도플러 주파수 추정에 관한 연구)

  • Lee, Jonggil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.17 no.7
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    • pp.1551-1557
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    • 2013
  • A current velocity measurement radar estimates Doppler frequencies to extract the corresponding surface velocity information. Therefore, it is required to maintain the high degree of reliability and accuracy of Doppler frequency estimates. However, Doppler spectra of water surface return echoes can have very widely varying shapes according to measurement environments and weather conditions. Therefore, serious problems may arise in maintaining the reliability and accuracy of conventional velocity estimating algorithm in a radar sensor. Therefore, in this paper, a newly suggested algorithm is proposed for improvement using estimation of peak Doppler frequencies. The proposed method shows that the more accurate velocity measurement can be possible comparing with the conventional one.

GPS Pull-In Search Using Reverse Directional Finite Rate of Innovation (FRI)

  • Kong, Seung-Hyun;Yoo, Kyungwoo
    • Journal of Positioning, Navigation, and Timing
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    • v.3 no.3
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    • pp.107-116
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    • 2014
  • When an incoming Global Positioning System (GPS) signal is acquired, pull-in search performs a finer search of the Doppler frequency of the incoming signal so that phase lock loop can be quickly stabilized and the receiver can produce an accurate pseudo-range measurement. However, increasing the accuracy of the Doppler frequency estimation often involves a higher computational cost for weaker GPS signals, which delays the position fix. In this paper, we show that the Doppler frequency detectable by a long coherent auto-correlation can be accurately estimated using a complex-weighted sum of consecutive short coherent auto-correlation outputs with a different Doppler frequency hypothesis, and by exploiting this we propose a noise resistant, low-cost and highly accurate Doppler frequency and phase estimation technique based on a reverse directional application of the finite rate of innovation (FRI) technique. We provide a performance and computational complexity analysis to show the feasibility of the proposed technique and compare the performance to conventional techniques using numerous Monte Carlo simulations.

A New Method for Extending Doppler Mean Frequency in Ultrasonic Imaging Systems (초음파 영상 시스템에서 새로운 도플러 평균주파수 확장 방법)

  • Kwon, Sung-Jae
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.8 no.5
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    • pp.1047-1056
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    • 2007
  • Basically, an ultrasonic imaging system has two fundamental imaging modes available. One is the B-mode imaging modality which provides an image of reflection coefficient, and the other is the Doppler color flow mode that maps blood flow inside the human heart and blood vessels. This paper presents a new method of detecting and compensating for aliasing that occurs when the Doppler frequency exceeds one-half of the pulse-repetition frequency (PRF). Its validity is shown by computer simulation. The new method not only extends the measurable Doppler frequency, but also helps to reduce the effect of noise. The results show that the aliasing can be compensated for correctly fur signal-to-noise ratios down to 20 dB.

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Laser Doppler blood flowmeter using self-mixing effect for the measurement of tissue blood flow. (조직혈류측정을 위한 자기혼합형 레이저 도플러 혈류계의 검토.)

  • Ko, Han-Woo;Choi, Duck-Hee
    • Proceedings of the KOSOMBE Conference
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    • v.1993 no.11
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    • pp.67-70
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    • 1993
  • This preliminary study describes the self-mixing effect of laser diode for the measurement of tissue blood flow. A self-mixing effect of laser diode was detected by the single-mode laser diode and the moving target, and the Doppler shifted frequency was thanked linearly with the driving frequency of speaker. The measured Doppler shifted frequency was compared with the simulated data.

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A Study on Effects of Antenna Diversity in Doppler Spread Environments (도플러 확산 환경에서의 안테나 다이버시티 효과에 관한 연구)

  • Lee Jong-Gil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.9 no.3
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    • pp.510-515
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    • 2005
  • Doppler spread can occur due to the relative movement of transmitter and receiver. The Doppler frequency shift varies as the relative location and the velocity of transceivers change. This Doppler spread may seriously degrade the performance of OFDM system which is considered to be very efficient for multimedia wireless communication. Therefore, applying the method of receiver diversity, we analyze the degree of BER improvement in Doppler spread environments to investigate the effectiveness of the chosen methods according to various wireless channels.