• 대한전자공학회논문지
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• 제26권5호
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• pp.32-37
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• 1989

Tschebyscheff 배열 방법에 의한 중앙급전식 구형도파관 공진형 슬롯배열 안테나의 설계방법을 제시한다. 도파관슬롯의 어드미턴스는 슬롯간의 상호결합 작용을 고려하여 실험 및 이론적 방법으로 구한다. 주파수 9.4GHz에서 동작하는 길이 1.8피이트의 공진형 슬롯배열 안테나를 설계제작하였다. 실험결과는 이득 25.5dB. 부엽준위 최대-22dB 및 반치각 $3.6^{circ}$로서 매우좋은 특성을 나타내었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.1335-1338
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• 2002

This paper presents the analysis of the required limit on a multibeam active phased array antenna (APAA) aperture using the statistical simulation for a High Altitude Platform Station (HAPS). The simulation takes into account the random errors caused by the non-identity of the array elements and the inaccuracy of the antenna calibration. The results of our statistical simulation show that the strict requirements on the sidelobe envelope for HAPSs can be met when the amplitude and phase distribution errors are minor, a condition which may be achieved by using digital beam forming.

• 전자공학회논문지A
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• 제32A권1호
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• pp.36-44
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• 1995

For a parabolic reflector antenna, a simple method is presented for computing efficiently the average power pattern degradations caused by the surface roughness of the reflector and misalignments between the reflector and the feed. In this procedure, both nonuniform surface errors and nonuniform illuminations are employed. The assumptions to derive the expressions are that in each annular region of the antenna, the rms value of the surface roughness is known, and in a zone in a annular region, the phase error by misalignments is constant, and can be taken to its value at the center of the zone. Detailed parametric studies are performed with derived expressions to determine the effects of those errors and illumination tapers on parameters such as gain and sidelobe levels.

• 전자공학회논문지A
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• 제31A권12호
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• pp.9-15
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• 1994

In this paper, the linearized power amplifier using digital adaptive predistorter is implemented in order to restrict spectral spreading and adjacent channel interference. The linearized systems is composed of a DSP56001 processor that executes predistortion in baseband. 90.deg. phase shifter, power splitter/combiner, quadrature modulator/demodulator of 360MHz band, and nonlinear amplifier. A ${\pi}$/4-shift QPSK is used to modulate digital random signals. As the quantized power of baseband signal and the output of amplifier are fed to the predistorter, and predistorting values are calculated using an adaptive algorithm. In the experiment, a peak to sidelobe ratio of the linearized amplifier is improved up to 15dB in comparison with conventional nonlinear amplifier, which means that the distortion of transmitted signal is decreased and adjacent channel interference was reduced.

• 한국소음진동공학회논문집
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• 제16권7호
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• pp.677-682
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• 2006

In the case of aeroacoustic test in windtunnel, measurement accuracy is reduced by not only Doppler effects but also by the microphone self noise due to airflow and high turbulence in the wall boundary layer. Microphone array measurements can be easily utilized for the solutions of these problems. In this paper, geometrical optics approach and diagonal term elimination of cross spectral matrix was introduced to the de-dopplerization and self noise reduction methods for the microphone array measurement. For the validation, beamforming tests for sinusoidal point source were performed in the closed type test section of windtunnel, and their performances of beam width and sidelobe rejection were significantly improved.

• 전자공학회논문지A
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• 제28A권10호
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• pp.791-798
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• 1991

In this paper, microstrip array antenna with the phase lock are designed to consist of main lobe and sidelobe with difference 21.97dB for sharp beam pattern using Tchebyscheff polynominals. Microstrip array antenna with phase lock of 0$^{\circ}$, 45$^{\circ}$, 90$^{\circ}$ are designed, to scan beam for 0$^{\circ}$, 6$^{\circ}$, 12$^{\circ}$ to be 1:2:2:1 for the relative current distribution. The designed microstrip array antenna with phase lock is measured in terms of various characteristics such as return loss, resonant frequency, radiation pattern, bandwidth, beamwidth, and the measurement value and theoretical value agreed with each other. Also, the patch array antenna with the relative current distribution is presented phase shift for beam scanning.

• 전자공학회논문지B
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• 제31B권4호
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• pp.18-29
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• 1994

For the efficient recognition of Korean Alphabets, we proposed the tree structure algorithm which was based on K-tuple NRF-SDF using representative images as training images. Representative images consisted of ECP-SDF images of several consonants or vowels. To reduce the effect of sidelobe in the output correlation plane, we used the representative images as training images and obtained the elements of a vector inner product matrix using the peak value of AMPOF correlation of training images with one another. The proposed algorithm consisted of three main-step containing several substeps. In filter synthesis of each step, representative images were used as training images in the first and the second main-step and each consonant or vowel was used as training images in the third main-step. The performance of this algorithm is demonstrated by computer simulation and optical experiment.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.131-135
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• 2003

WDM(Wavelength division multiplexing) light wave communication system requires MUX/DeMUX and optical filter OADM can be used to extract and add the specific wavelength channel from the transmission line. In this paper, we propose the OADM based on MZI and cascade FBG. It is able to minimize system and reduce sidelobe. So, we have considered MZI structure and 3dB coupler. Using the coupled mode theory. We also analyze out characteristics of OADM and experiment. From results obtained by experiment and computer. Simulation, the proposed OADM with cascade FBG works well. we hope that the obtained result in this paper con be used as the data to design the OADM with cascade FBG.

• 대한의용생체공학회:의공학회지
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• 제17권2호
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• pp.189-200
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• 1996

In this paper, we compared the performance of the Kaiser window with those of others as a weight function of well known anodization technique for regression of side lobe in a field pattern resulted from focusing of transducer array. The Kaiser window is an window providing many types of curve with several variables. In order to compare performance of the Kaiser window as the weight function, anodization results of the previously used Hamming window function and the Matched Gaussian function are compared Result of computer simulation, the pertormance of Kaiser window with $\delta$=0.0025 in side lobe regression was better than that of Hamming window or Matched Gausian function.

• 말소리와 음성과학
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• 제1권3호
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• pp.95-102
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• 2009

In this paper, an efficient target speech detection algorithm is proposed for the performance improvement of multi-input speech enhancement. Using the normalized cross correlation value between two selected channels, the proposed algorithm estimates the probabilistic distribution function of the value from the pure noise interval. Then, log-likelihoods are calculated with the function and the normalized cross correlation value to detect the target speech interval precisely. The detection results are applied to the generalized sidelobe canceller-based algorithm. Experimental results show that the proposed algorithm significantly improves the speech recognition performance and the signal-to-noise ratios.