• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.114-125
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• 2014

In a conventional sonar system, which uses LFM signal for detecting targets with varying speed, the results of multiple LFM Doppler correlators are aligned and the maximum alined result are selected as a test cell for detecting targets. As the number of the LFM Doppler correlators are increased for accurate target detection, as the required computational complexity and the memory are also increased. This fact makes it difficult to implement the accurate LFM target detector. In this paper, we propose a new fast target detection which is robust for the variation of target speed. Because the proposed method uses the summation of alined results of large numbers of LFM Doppler correlators, the proposed method increase SNR and provide robust SNR for the variation of target speed. And the proposed method can provide very fast target detection by implementing the process, the summation of alined results of large numbers of LFM Doppler correlators, as one summation filter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.166-176
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• 2000

In this paper, the LEO system signal degradation is mainly due to fading and doppler shift, so that the analysis of the signal degradation and compensation techniques are very important. This paper propose a Kalman filter based two step Automatic Frequency Control(AFC) to combat large and time variant frequency offset in low earth orbit satellite communication systems. The proposed Kalman AFC method estimates a frequency offset in two steps, I. e., coarse and fine estimations, extending the frequency acquisition range to even for than the symbol rate. Furthermore, it can track well a time variation of frequency offset. It is shown that the proposed compensator is able to compensate for doppler shift more than several KHz.

• Journal of Biomedical Engineering Research
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• v.20 no.3
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• pp.275-281
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• 1999

Conventional PW Doppler systems suffer from the ambiguity of measured blood velocities due to the spectrum aliasing when the corresponding Doppler frequencies are greater than the Nyquist frequency. Base-line shift is a customary method for dealiasing the Doppler spectrums. I lowever, Doppler audio signals still remain unchanged even when the base-line shift method is applied. This paper de scribes an method for dealiasing both the Doppler spectra and audio signals by using sampling rate expansion, frequency shifting, and filtering poerations. For undirectional flows, the method can increase the maximum detectable Doppler frequency from the Nyquist limit of one-half of the Pulse Repetition Frequency(PRF) to the PRF. Experiments with real data have been performed to verify the proposed method.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.48-55
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• 2009

The feedback interference channels are those made through the multipaths that are built by moving and stationary objects around transmit and receive antennas mounted at the same point. This paper describes the method to measure the feedback interference channels in the rural regions and sides of highways and the analysis on channel characteristic parameters. Using the measured samples, we estimated scattering functions, delay power spectra, and Doppler power spectra, and we analyzed the channels using eight parameters including coherence bandwidth, coherence time, maximum excess delay, average excess delay, rms delay spread, Doppler shift, Doppler spread, and spread factor, and delay and Doppler cumulative distributions. Even though many observations are made, note that the feedback signals of high Doppler frequencies and large energy are observed in the sides of highways due to high speed vehicles while low Doppler frequencies occurred in the rural region due to rare traffic.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.2
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• pp.75-82
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• 2001

In this paper, a transmitter and a receiver using a Gunn diode and SBD was designed and fabricated in X-band. This system detects Doppler shift signal reflected by moving target through the homodyne detection, which is Doppler radar sensor for the measurement of the velocity of moving target. By the experimental results, the oscillating condition of the transmitter was satisfied at about the half wavelength between the supporting post of the Gunn diode in the waveguide and the waveguide short. And using the fabricated Doppler radar sensor, the velocity measurement deviation of moving target was 1.24%.

• Journal of Satellite, Information and Communications
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• v.4 no.1
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• pp.21-27
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• 2009

In this paper, we introduce a simulation result of cross ambiguity function (CAF) using time difference of arrival and frequency difference of arrival. This method is generally used to find a geographical location of the unknown radio transmitter. If multiple signals with the same source information are arrived at a receiver via different paths, then they will have different time delays and Doppler shifts. We can estimate the CAF by using these characteristics, and estimate the location of the unknown transmitter. This paper introduces a technique to improve the estimation performance of CAF.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.3
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• pp.301-307
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• 2024

In this paper, we propose a round trip time (RTT)-enabled Doppler-based positioning method considering the low earth orbit (LEO) satellite visibility restriction. Doppler-based positioning typically requires visibility to at least eight satellites, which is often unfeasible due to the limited coverage of LEO satellites, as beamforming technique is applied to current LEO satellites. To solve this problem, we utilize the RTT measurements, assuming that a communication link exists between the user equipment (UE) and LEO satellites. We employ the Newton-Raphson method to estimate the UE position with RTT and Doppler measurements. We analyze the positioning performance of the considered framework via simulation, demonstrating its performance in 3D positioning errors under varying satellite numbers and measurement errors.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.313-316
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• 2000

본 논문에서는 동적 다중경로 환경에 대한 DTV수신 성능 개선을 위하여 정보 데이터 세그먼트 부분에서는 Stop and Go 알고리즘을 사용하고 313 세그먼트 중 한 개만이 훈련열로 쓰이는 기존의 ATSC 표준의 데이터 프레임 구조보다 더 많은 훈련열이 들어있는 새로운 데이터 프레임 구조를 제안한다. 정보가 없는 널 패킷을 훈련열로 대체하기 때문에 데이터의 손실 없이 더 많은 훈련열을 사용하여 특히 동적 다중경로 환경에서 등화기의 수렴 특성을 개선할 수 있다. 전산 모의 실험을 통하여 동적 다중경로 환경의 도플러 천이에 대한 시스템 수신 성능의 개선을 확인하였다.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.294-297
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• 2002

ADP(Acoustic Current Profiler)는 수중에서 음파를 발사하여 해수와 함께 유동하는 부유입자에 의하여 반사되는 음향의 Doppler 효과를 이용하여 여러 개의 수층에서 유속과 유향을 측정하는 장비이다. Doppler 효과에 의한 반사음향의 주파수 천이가 부유입자의 속도에 따라 달라지는 것을 이용하여 해수의 흐름을 관측할 수 있다. (중략)

• Journal of IKEEE
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• v.15 no.1
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• pp.49-56
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• 2011

In this paper, a compact doppler sensor with oscillator type active antenna operating at 2.4GHz frequency band is proposed to measure the distance or speed of a moving object. The active antenna has been realized by oscillator using radiator, patch antenna, as its resonator. The oscillation frequency is shifted depending on approaching of the object, and a detection circuit discriminates the frequency deviation. The oscillator type active antenna has been designed and simulated. The prototype fabricated has a very small circular disk type of diameter 30mm and height 4.2mm. As for antenna performance, broadside radiation pattern with beamwidth of $130^{\circ}$ and oscillation frequency of 2.373GHz has been measured. Test results as a doppler sensor shows that doppler signal voltage of about 190mV has been obtained for conducting plate moving 1 meter away from the sensor. And, doppler signal voltage has been linearly increased to the ground from 4.5m height by free-falling the sensor.