• Journal of Biomedical Engineering Research
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• v.10 no.1
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• pp.33-42
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• 1989

The doppler effect is used for measuring the velocity of the blood flow in artery. Because of the range information, the pulsed doppler system is most commonly used. In this paper, we propose a new two-dimensional(2-D) pulsed Doppler system. Which uses second-order sampling method and serial processing. The proposed system using second-order sampling method eliminates in-phase, quadrature-phase balancing problem at demodulator of quadrature detection method. In addition, the new pulsed 2-D doppler system eliminates balancing problem of channels of 2-D doppler system because of serial processing.

• Korean Journal of Optics and Photonics
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• v.32 no.3
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• pp.108-113
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• 2021

We propose and experimentally demonstrate a method of remote sound extraction using laser Doppler interferometry. The output frequency of a laser Doppler interferometer changes to be the same as the frequency of the acoustic wave from than object vibrated by the sound due to the Doppler effect. Based on this phenomenon, we measure the vibrational frequency of a remote target affected by a sound wave in real time, via laser Doppler interferometry. We track the peak frequency of the interferometer's output via appropriate signal processing, which confirms that the characteristics of the so detected wave are the same as that of the original sound source. We also confirm that the same method can retrieve the sound waves not only from remote sources of single tones, but from those of any sound.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.947-952
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• 2015

To supplement energy needs and take advantage of renewable energy sources, many wind farms are currently being built in mountainous areas under the supervision of the Korean government. However, operation of these wind farms can cause serious threats to national security due to Doppler modulation from the wind turbines causing interference with military radar operating in the vicinity. Therefore it is necessary to develop methods to analyze the Doppler frequency during the operation of wind turbines and the effect on radar signals. Based on modeling of the mountainous region, blockage analysis, turbine motion and the radar signals, this paper proposes a signal processing method to extract and analyze the Doppler frequency. Simulation results showed the change of Doppler frequency over time caused by the geometry of the mountainous area and the wind turbine.

• The Journal of the Acoustical Society of Korea
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• v.25 no.3
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• pp.113-120
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• 2006

This paper is concerned with a equalization technique for Orthogonal Frequency Division Multiplexing (OFDM) systems based on a block type pilot arrangement over slow fading channels. The bit rates obtained in underwater channels are relatively modest compared to some other communication channels such as cellular phones or indoor wireless systems. Consequently. the Doppler effect is the important parameter in tracking a channel. In case of a coherent demodulation scheme, the residual mean phase errors due to Doppler frequency may be fatal for the performance of the system. The equalizer could not solely handle mean Doppler shift. To account for the common Doppler effect a phase error tracking loop is used with the frequency equalizer. so that the rotation errors are avoided. Furthermore. simulations show that we can reduce the computational load of the tracking loop with negligible effect on performance.

• Journal of the Korea Society for Simulation
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• v.12 no.4
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• pp.17-24
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• 2003

In this paper, we propose a model that simulates the reflective waveform from underwater objects by means of Doppler effect, highlight and elongation phenomenon. Also, this paper presents a hardware Implementation of simulation model with the input and output parameters. The underwater target simulator consists of transducer, receiver, transmitter and control parts. According to the experimental results of the simulator, it carried out the performances of real target in response to transmission signal.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.327-330
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• 2015

Cosmology considers the Hubble redshift of galaxy light by the Doppler effect as proof the Universe has been expanding since the Big Bang. However, cosmic dust that permeates the Universe also redshifts galaxy light that if not corrected over-predicts the velocities of all astronomical measurements inferred by the Doppler effect. Hubble redshifts corrected for cosmic dust suggest the Universe may not be expanding, the consequence of which may allow the outstanding problems in cosmology to possibly be resolved by Newtonian mechanics.

• The Journal of the Acoustical Society of Korea
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• v.9 no.3
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• pp.48-55
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• 1990

We analyze the effect of second-order sampling on estimating the mean frequency of the Doppler signal. In order to reduce the sampling frequency of analogue-to-digital converter, it is possible to obtain the Doppler signal by sampling the radio frequency echo signal with the low frequence of $4f_0$/5 or $4f_0$/9 instead of $4f_0$, where $f_0$ is the center frequency of the transmitted signal. The computer simulation and experiments show that if the narrowband signal is transmitted as is usual in the Doppler system, the error of the mean frequency estimates due to the low sampling frequency is negligible.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5513-5529
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• 2016

Doppler Effect is a prominent obstacle in vehicular networks, which dramatically increase the Bit-Error-Rate (BER). This problem is accompanied with the presence of the Orthogonal Frequency Division Multiplexing (OFDM) systems in which the Doppler shift interrupts the subcarriers orthogonality. Additionally, Inter-Symbol Interference (ISI) and high Peak-to-Average Power Ratio (PAPR) are likely to occur which corrupt the received signal. In this paper, the single-carrier combined with the frequency domain equalizer (SC-FDE) is utilized as an alternative to the OFDM over the IEEE 802.11p uplink vehicular channels. The Minimum Mean Squared Error (MMSE) and Zero-Forcing (ZF) are employed in order to study the impact of these equalization techniques along with the SC-FDE on the propagation medium. In addition, we aim to enhance the BER, improve the transmitted signal quality and achieve ISI and PAPR mitigation. The proposed schemes are investigated and we found that the MMSE outperforms the ZF equalization under different Doppler shift effects and modulations.

• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.1
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• pp.106-115
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• 2000

This paper presents the measuring technique of time and velocity when rocket motor is burnt out for 2.751" rocket. This technique use doppler effect, frequency spectrum analysis and curve fitting. In this study, we use muzzle velocity radar for doppler signal acquisition, short-time fourier transform for spectrum analysis and curve fitting for smoothing.

• Journal of the Korean Institute of Navigation
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• v.5 no.2
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• pp.1-39
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• 1981

A doppler log is the typical device which can measure the ship's speed over the ground directly, by means of doppler effect of the underwater ultrasonic wave, which involves the error due to the sea bottom inclination, the trim and the incorrect transducer installation etc. The present doppler log adopts a single transducer, faced in the direction of themain beam, and therefore it is unable to correct the beam direction to eliminate the above mentioned error. Moreover, the frequencyis also limitted in a comparatively high range for getting a sharp beam with single transducer, and the speed over the ground can not be detectable at the deep sea, for an instance, over 200 meters. This paper describes a theoretical consideration for the doppler log error and an analysis by a computer on the observed speed data by a full size model ship. The result is verified that the most of doppler log error is caused by the ultrasonic beam angle of transducer. To eliminate the doppler log error due to the incorrect transducer installation and also to sharpen the beam for lower frequency range to expand measurable sea depth, this paper proposes a method of controlling the directivity adopting a linear transducer array and of controlling the directivity by the control of exciting current, and investigates by the computer simulation and make experiment with magnetostrictive ferrite transducer of 28, 50 and 75KHz. The experimental results are shown well coincide with the measured ones, and they are revealed that in case where the transducer interval is greater than 1 wavelength, the effective control of the beam direction is hardly performed with keeping adequate beam width and side lobe level. It is concluded that 6-elements array with inter element space of a half wavelength can make comparatively sharp beam and low side lobe level. The results obtained here will contribute very much to the improvement of the performance of doppler log.