• Title, Summary, Keyword: 도플러

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General Derivation of the Doppler Effect by Using a Space-Time Graph and Its Application (시공 그래프를 이용한 도플러 효과의 일반적 유도와 적용)

  • Kim, Gyhyuk
    • New Physics: Sae Mulli
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    • v.67 no.11
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    • pp.1342-1347
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    • 2017
  • We derived the Doppler effect from geometric analysis of a space-time graph and found the general solution of the Doppler effect for 3-dimensional plane wave and spherical wave. In our general solution, we were able to treat symmetrically the motion of the wave source and that of detector and to integrate the formulas for the elastic wave and the light. Applying the formula to a relativistic aberration, we presented a simpler explanation of related physical concepts. In the case of 3-dimensional spherical waves, we expected a new transverse Doppler effect. The geometric derivation of the Doppler effect should allow students to study the Doppler effect more consistently and systematically.

Noncontact Respiration and Heartbeat Monitoring System using the Doppler Radar System (2.4GHz 도플러 레이더를 이용한 비접촉 방식의 심박 및 호흡 모니터링 시스템)

  • Shin, Jae-Yeon;Cho, Sung-Pil;Jang, Byung-Jun;Park, Ho-Dong;Lee, Kyoung-Joung
    • Proceedings of the KIEE Conference
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    • pp.478-479
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    • 2008
  • 본 연구에서는 비접촉 방식으로 심박과 호흡을 측정하기 위해 2.4GHz 대역에서 동작하는 도플러 레이더 센서와 베이스밴드 모듈로 구성된 도플러 레이더 시스템을 설계하고 그 성능을 평가하였다. 설계된 도플러 레이더 시스템은 심폐활동에 의한 흉부 표면의 움직임에 의해 반사되는 레이더의 위상변화를 이용하여 심폐 활동을 측정한다. 도플러 레이더 센서의 출력은 베이스 밴드 모듈의 전처리 필터부, 증폭부, 오프셋 조정부를 통과하여 호흡과 심박 신호로 분리된다. 분리된 생체신호는 기존의 생체신호와 상관성을 확인하기 위해 기준신호로 호흡과 심전도를 동시에 측정하여 그 결과를 비교 및 분석하였다. 설계된 도플러 레이더 시스템에서 분리된 호흡 및 심박 신호는 측정 대상의 움직임이 없는 상태에서는 높은 검출률을 보였으며, 도플러 레이더에서 심박과 호흡 신호를 검출한 결과 거리, 호흡과 심박의 변이량, 호흡과 심박대역에 따라 검출률이 영향을 받는다는 것을 알 수 있었다.

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이중광속을 이용한 레이저 도플러 속도 측정계(Fiber optic sensors 시스템 기술 개발연구)

  • 이형종
    • Proceedings of the Optical Society of Korea Conference
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    • pp.134-139
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    • 1989
  • 레이저 도플러 효과를 써서 유체 또는 작은 입자의 속도를 잴수 있는 레이저 도플러 속도측정 장치를 만들었다. 광학계는 레이저 광속을 두 갈래로 나누어 다시 마주치게 하여 두 광속이 겹치는 곳에, 평행한 삼차원 간섭무늬가 생기도록 꾸몄다. 분무기로 작은 물방울을 만들어 두 광속이 겹치는 곳을 지나게 했더니 도플러 신호를 얻을 수 있었다.

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Influence to the Doppler Images by the Defects of SAE in the Probe of Medical Ultrasonic Scanners (초음파 프로브에서 인접 단위 소자군(SAE) 결함이 도플러 영상에 미치는 영향)

  • Lee, Kyung-Sung
    • Journal of radiological science and technology
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    • v.38 no.1
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    • pp.7-15
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    • 2015
  • A ultrasonic probe is very important in medical ultrasonic image, but the frequency of probe defects are often. Therefore practical tools for probe based ultrasonic QA should be developed. Advanced research on the effects of the probe defects on the quality of ultrasonic images is required. This study has investigated the effects of the defects in the probe elements influence Doppler images in the medical ultrasonic scanners. Especially the defects in a set of adjacent elements(SAE) electrically disconnected influence Doppler images were tested. The results show Doppler brightness and velocity became rapidly reduced as the defected elements is located centrally, as the defected elements is activated. The more the defected elements increased, the more Doppler brightness and velocity increased. As a set of the element disconnected moved, it appeared Doppler velocity starting to decrease and then was followed by brightness. The strength is not consistent with the velocity in the number and location of the defected elements. The defects in the probe elements influence Doppler velocity when the defected elements got out of the elements activated at Doppler mode.

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.

A Basic Study on the Measurement of Velocity Distribution of Underwater Targets (수중 물체의 속도 분포 측정에 관한 기초 연구)

  • 이은방;이상집
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.2 no.1
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    • pp.1-10
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    • 1996
  • 초음파는 액체 및 고체의 매질 속에서도 그 전달 특성이 우수하여 수중 물체의 감지, 지질 조사 자원탐사뿐만 아니라, 의학 분야에서도 널리 사용되고 있다. 물체유동정보 측정방식에는 연속파를 이용한 도플러식과 펄스 신호를 이용한 도플러는 거리 분해능이 좋으므로 깊이에 따른 속도 정보를 쉽게 얻을 수 있는 장점이 있으나, 수신되는 도플러 신호가 탐촉자의 특성과 매질 속에서의 전파특성 등에 의하여 송신된 신호와 파형이 다르고 복잡한 주파수 특성을 가지므로 연속파에서와 같이 도플러 주파수를 직접 측정하기 곤란하다. 도플러 주파수를 검출하기 위하여 여러 방법이 개발되어 있으나, 측정거리와 측정속도의 제약과 더불어, 실시간(real time) 처리에 의한 분포적 측정이 어려운 실정이다. 본 연구에서는 시간 영역에서 국소 데이터를 이용하여 펄스 신호의 위상을 정의하고 실시간에서 펄스 신호를 위상으로 변환하는 신호 처리법을 제안하였다. 또한 이 신호 처리법을 응용하여 측정 범위의 위상 곡선에서 위상 차를 계산함으로써 평균 가속도와 유동속도정보를 분포적으로 얻을 수 있는 새로운 펄스 도플러 기법을 제안하였으며, 모델 신호를 만들어 제안된 방법의 유용성을 검토하였다.

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The Impacts of Piezoelectric Elements' Defects On Color & Power Doppler Images (초음파 프로브에서 소자결함이 컬러 및 파워 도플러 영상에 미치는 영향)

  • Lee, Kyung-Sung
    • Journal of radiological science and technology
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    • v.38 no.4
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    • pp.443-449
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    • 2015
  • An ultrasound probe has a big impact on Doppler images even though it has very high risk of frequent function-breakdowns occurring in medical ultrasound scanners. This study experimentally analyses the impacts of an ultrasonic probe's defected elements on power & color Doppler images. The results show that, the bigger the size of defected probe elements is, and the closer a group of action elements is to the center, the more the brightness of images and the velocity of Doppler diminish. When elements' defects increase in color & power Doppler images, false images are formed to be mistaken for blood-vessel plaque in neighboring regions. Accordingly, whenever element defects are suspected, we need check-up process in B-mode. From this respective, it is advisable to have primary interest in a probe and carry out continuous probe QA for ultrasonography.

The Relative Position Estimate of the Moving Distributed Sources Using the Doppler Scanning Technique (도플러 스캐닝 기법을 이용한 이동하는 다중 음원의 상대 위치 추적 기법)

  • 노용주;윤종락;전재진
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.5
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    • pp.446-454
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    • 2002
  • This paper presents the Doppler Scanning technique which enables us to detect the relative positions of moving distributed sources using Doppler frequency shift estimate when the moving source consists of distributed sources with different signature frequencies. Doppler frequency shifts of characteristic frequencies of machinery noise sources such as ship's generator and propeller, with tine along CPA (Closest Point of Approach of moving source) are unique, and can be functioned with respect to each source position. Therefore, this technique can be applied to estimate the relative geometrical positions between machinery noise sources. The Extended Kalman Filter (EKF) which has a high frequency resolution with high time resolution, is adopted for improving accuracy of Doppler frequency shift estimate geometric resolution of machinery positions since machinery noise sources show in general low frequency band characteristics with limited spacial distance. The performance of the technique is examined by the numerical simulations and is verified by the experiment using loudspeaker sources on the roof of the car.

Development of Ultrasound Sector B-Scanner(III)-Pulsed Ultrasonic Doppler System- (초음파 섹터 B-스캐너의 개발(III)-초음파 펄스 도플러 장치-)

  • 백광렬;안영복
    • Journal of Biomedical Engineering Research
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    • v.7 no.2
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    • pp.139-146
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    • 1986
  • Pulsed ultrasonic Doppler system is a useful diagnostic instrument to measure blood-flow-velocity, velocity profile, and volume-blood-flow. This system is more powerful compare with 2-dimensional B-scan tissue image. A system has been deve- loped and ii being evaluated using TMS 32010 DSP. We use this DSP for the purpose of real-time spectrum analyzer to obtain spectrogram in singlegate pulsed Doppler system and for the serial comb filter to cancel clutter and zero crossing counter to estimate Doppler mean frequency in multigate pulsed Doppler system. The Doppler shift of the backscattered signals is sensed in a phase detector. This Doppler signal corresponds to the mean velocity over a some region in space defined by the ultrasonic beam dimensions, transmitted pulse duration, and transducer ban(iwidth. Multi- gate pulsed Doppler system enable the transcutaneous and simultaneous assessment of the velocities in a number of adjacent sample volumes as a continuous function of time. A multigate pulsed Doppler system processing the information originating from presented.

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A Study on Simulation of Asymmetric Doppler Signals in a Weather Radar (기상 레이다에서의 비대칭 도플러 신호 모의구현에 관한 연구)

  • Lee, Jong-Gil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.12 no.10
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    • pp.1737-1743
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    • 2008
  • A weather radar extracts the weather information from the return echoes which consist of scattered electromagnetic wave signals from rain, cloud and dust particles, etc. The characteristics of Doppler weather signal and ground clutter should be analyzed to extract the accurate weather information. However, the conventional symmetric weather Doppler model is somewhat inappropriate in representing various weather situations. Therefore, the improved model is suggested to describe the skewness in the Doppler spectrum model. Using the suggested model, many various weather signals can be simulated efficiently in time and spectral domain according to weather situations, operation environment and system characteristics. This simulation method may be very helpful in verifying the accuracy of the weather information extraction algorithms and developing the new system for further performance improvement.