• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2101-2107
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• 2012

A current velocity measurement radar for a river or a stream estimates Doppler frequencies of return echoes to extract the corresponding surface velocity information. It is very important to maintain the reliability and accuracy of these velocity estimates for water resource management such as flooding or drought conditions. However, received Doppler spectra of water surface return echoes have very widely varying shapes according to different measurement environments and weather conditions. Therefore, serious problems may arise in maintaining the reliability and accuracy of velocity estimating algorithm in a radar sensor because of Doppler spectra which can have many different kind of shapes. Therefore, in this paper, an appropriate Doppler spectrum model is suggested to simulate many various Doppler spectra. This model can be very useful in validating the reliability and accuracy of surface velocity estimates.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.956-957
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• 2014

In a fluid velocity measurement radar, the velocity information can be extracted from Doppler spectrum estimates of the return signal. However, the Doppler frequency ranges are too low for the case of low velocity profile measurements resulting in the serious effects in the velocity measurement. Therefore, the improved method is analyzed to overcome this problem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6A
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• pp.586-592
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• 2006

In this paper, a novel detection method called the joint multiple frequency cell (JMFC) detection is addressed for spread spectrum code acquisition in the presence of residual Doppler frequency offset (RDFO). When the RDFO exists, the correlation peak used for detection during the acquisition process is split into several lower neighboring peaks, resulting in severe degradation in the detection performance, and consequently, in the overall acquisition performance. In the JMFC detection, a decision variable for detection is formed by combining several consecutive correlator outputs, so that the reduction in the correlation value due to the RDFO can be alleviated. Numerical results show that the proposed scheme can offer better detection performance over the conventional scheme based on the cell-by-cell detection.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.9
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• pp.1999-2005
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• 2015

A wind velocity is measured in a weather radar as well as the strength of return echoes from rain clouds. These wind velocities are obtained through estimation of Doppler frequencies in return signals. This kind of Doppler frequency estimation method is called as a correlation method. It is widely used in most weather radars because of less computation time. However, it may cause serious errors if a spectrum is not symmetric. Therefore, in this paper, it is shown that the improved method using 3^rd order phase estimation model yields the more accurate estimation of the average Doppler frequency using various simulated weather data.

• Journal of Biomedical Engineering Research
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• v.7 no.2
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• pp.169-182
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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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.853-856
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• 2007

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 acquisition of accurate weather information depends on the operation environment which include the Doppler weather signal and ground clutter characteristics. Since the conventional symmetric weather Doppler model does not represent the measurements in real situations, 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 to verify the accuracy of signal processing algorithms and the reliability of the extracted weather information

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3A
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• pp.205-210
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• 2002

In a Doppler weather radar, high resolution windspeed profile measurements are needed to provide the reliable detection of hazardous weather conditions. For this purpose, the pulse pair method is generally considered to be the most efficient estimator, However, this estimator has some bias errors due to asymmetric spectra and may yield meaningless results in the case of a multimodal return spectrum. Although the poly-pulse pair method can reduce the bias errors of skewed weather spectra, the modes of spectrum may provide more reliable information than the statistical mean for the case of a multimodal or seriously skewed spectrum. Therefore, the idea of relatively simple mode estimator for a weather radar is developed in this paper, Performance simulations show promising results in the detection of hazardous weather conditions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.9
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• pp.1818-1825
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• 2017

An Acoustic Doppler Current Profiler(ADCP) measures the current velocity and analyzes the degree of turbulence using Doppler effects of ultrasonic waves. Therefore, the autocorrelation or FFT spectrum estimates are obtained for extraction of current velocity in each spatial region. However, if the correlation method does not satisfy the assumption that the return signal spectra are symmetric Gaussian, the large bias errors can occur. Also, the accurate estimation of autocorrelation or FFT spectrum is difficult due to the short acquisition interval when the rapid changes of current velocity occur. Thus, in this paper, the estimation method of the autoregressive spectrum peak is suggested for the accurate current velocity measurement of both symmetric and asymmetric spectra. It is shown that estimation quality can be improved using the suggested method comparing with the conventional methods. Many return signals under the various environment are simulated and the results are compared and analyzed for evaluation of the suggested method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1492-1499
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• 2020

A weather radar system generally shows the weather phenomena related with rainfall and wind velocity. These systems are usually very helpful to monitor the relatively high altitude weather situation for the wide and long range area. However, since the weather hazards due to the strong hail and heavy rainfall occurring locally are observed frequently in recent days, it is important to detect these wether phenomena. For this purpose, it is necessary to detect the fast varying low altitude weather conditions. In this environment, the effect of surface clutter is more evident and the antenna dwell time is much shorter. Therefore, the conventional Doppler spectrum estimation method may cause serious problems. In this paper, the AR(autoregressive) Doppler spectrum estimation methods were applied to solve these problems and the results were analyzed. Applied methods show that improved Doppler spectra can be obtained comparing with the conventional FFT(Fast Fourier Transform) method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.561-564
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• 2007

Recently, The detection of weather conditions and weather related hazards with a weather radar are being actively investigated based on the echo intensity and the Doppler spectrum analysis. For this purpose, many types of simulated weather signals are needed for investigation. Therefore, this paper analyzed the method to simulate the many weather radar signals.