• 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 Korea Society of Computer and Information
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• v.16 no.10
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• pp.137-145
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• 2011

In this paper, we modeled digital M/W transmission channel by frequency non-selective fading channel and analyzed the power spectrum magnitude of digital M/W transmission systems adopting OFDM modulation scheme through simulation. From the simulation results, it was found that deep does not appear in the specified fixed bandwidth under the AWGN environment. Also, lower power spectrum magnitude was shown in frequency non-selective fading channel than that in AWGN channel. Futhermore, the power spectrum magnitude value became more lowered when carrier frequency and vehicle speed became higher.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.9
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• pp.1641-1648
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• 2016

A weather radar estimates Doppler frequency and width of Doppler spectrum from the received weather signal which represents the return echoes from rain or dust particles in a corresponding area. These estimates are very important parameters since they are directly related to precipitation, wind velocity and degree of turbulence. Therefore, these estimated values should be highly reliable to obtain accurate weather information. However, the echoes of a weather radar include both the weather signal and the clutter which occurred from ground reflection or moving objects, etc. The existence of the clutter in the echoes may cause serious errors in the estimation of weather-related parameters. Therefore, in this paper, models are developed to represent the weather signal and the clutter for the purpose of analyzing estimation errors caused by the strong clutter echoes. Using these models, various return echoes according to the weather signal and clutter power are simulated to analyze the effects of the clutter.

• Journal of Biomedical Engineering Research
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• v.20 no.6
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• pp.531-537
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• 1999

본 연구에서는 FFT와 파라메트릭 방법에 의한 혈류 추정방법을 연구하고 디지털 신호처리 프로세서를 이용하여 레이저 도플러 혈률계를 구현하였다. 레이저 도플러 혈류계는 피부의 모세혈류의 흐름을 측정할수 있는 장비로서 다양한 분야에 활용이 가능하다. 구현된시스템은 TI사의 TMS320C32 DSP를 사용하였으며, 전력 스펙트럼의 모멘트값을 이용하여 혈류를 추정하였다. 혈류 추정 값은 매 0.5초마다 그래픽 사용자 인터페이스를 통해서 표시하도록 하였다. 시스템의 성능을 평가하기 위해서 혈류 시뮬레이터에 흐르는 혈류를 계단함수, 삼각함수, 사인함수로 제어하여 그 결과를 비교하였으며 인체 부위에 따른 혈류를 측정하였다. 실험결과 구현된시스템의 혈류 추정성 및 재현성이 보장되고있음을 확인할수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.9
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• pp.1123-1130
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• 2019

Simulation of the strong clutter occurring from the airborne radar is essential in the efficient development and performance evaluation of the aircraft radar system. If the efficient simulation of the clutter can be successful, algorithms can be proved and analyzed and also the performance evaluation is possible in the laboratory environment. Therefore, development and implementation of the airborne radar system can be achieved very economically in the effective way. However, the clutter simulation procedure is very difficult and tedious since the clutter environment changes in numerous ways as it depends on the flight path, direction of antenna beam, reflectivity of the surface, etc.. Thus, in this paper, the general Doppler spectrum model is suggested for efficient simulation of the various clutter environment. Also, it is shown that the various type of clutter in time domain can be generated easily by changing and adjustment of parameters in the general Doppler spectrum model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2187-2193
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• 2010

A specific radar system can be implemented more easily using the frequency modulated continuous wave comparing with the pulse Doppler radar. It also has the advantage of LPI (low probability of interception) because of the low power and wide bandwidth characteristics. These radars are usually used to cover the short range area and to obtain the high resolution measurements of the target range and velocity information. The transmitted waveform is used in the mixer to demodulate the received echo signal and the resulting beat signal can be obtained. This beat signal is analyzed using the FFT method for the purpose of clutter removal, detection of a target, extraction of velocity and range information, etc. However, for the case of short signal acquisition time, this FFT method can cause the serious leakage effect which disables the detection of weaker echo signals masked by strong side lobes of the clutter. Therefore, in this paper, the weighting window method is analyzed to suppress the strong side lobes while maintaining the proper main lobe width. Also, the results of FFT beat spectrum analysis are shown under various environments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.3
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• pp.390-394
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• 2003

It is very important to simulate various mobile communication channels for the reliable system design and performance tests. Therefore, a new method is proposed in this paper to improve the conventional one for the purpose of the efficient channel simulation having various characteristics. A newly proposed method can simulate any narrow band channel very efficiently from the given Doppler power spectrum model. Also, it has many simulation advantages considering the variety of wireless channel conditions since parameters related with channel characteristics, such as a signal power, signal to noise ratio, direct signal power ratio, etc., can be easily changed according to various propagation environments to be tested.