• Journal of Satellite, Information and Communications
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• v.8 no.2
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• pp.88-93
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• 2013

The wideband chirp signal generator to enhance the resolution of synthetic aperture radar of obtaining the earth observation image is needed. This paper deals with designing, manufacturing and testing the wideband digital chirp signal generator having high resolution for LEO earth observation satellite. The wideband digital chirp signal generator is implemented with the memory-map based structure which is mostly applied in the satellite, and consists of the digital module to generate the digital chirp signal and the RF module to perform the quadrature modulation. The I/Q signals stored in the memory of the digital module are D/A converted and delivered to be quadrature modulated with the reference signal of 1275 MHz in the RF module. Furthermore, the test bench and GUI to validate the signal generator function are also developed. It is found that the requirement of 144 MHz bandwidth for the digital chirp signal generator is well met. Finally it is noteworthy that the distortion occurred in the chirp signal generator was compensated by the pre-distortion compensation.

• Honam Mathematical Journal
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• v.16 no.1
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• pp.119-135
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• 1994

Let $Q_{n+p-1}(\alpha)$ denote the- dass of functions $$f(z)=z^{P}-\sum_{n=0}^\infty{a_{(p+k)}z^{p+k}$$ ($a_{p+k}{\geq}0$, $p{\in}N=\left{1,2,{\cdots}\right}$) which are analytic and p-valent in the unit disc $U=\left{z:{\mid}z:{\mid}<1\right}$ and satisfying $Re\left{\frac{D^{n+p-1}f(\approx))^{\prime}}{pz^{p-a}\right}>{\alpha},0{\leq}{\alpha}<1,n>-p,z{\in}U.$ In this paper we obtain sharp results concerning coefficient estimates, distortion theorem, closure theorems and radii of p-valent close-to- convexity, starlikeness and convexity for the class $Q_{n+p-1}$ ($\alpha$). We also obtain class preserving integral operators of the form $F(z)=\frac{c+p}{z^{c}}\int_{o}^{z}t^{c-1}f(t)dt.$ c>-p $F\left(z\right)=\frac{c+p}{z^{c}}\int_{0}^{z} t^{c-1}f\left(t \right)dt. \qquad c>-p$ for the class $Q_{n+p-1}$ ($\alpha$). Conversely when $F(z){\in}Q_{n+p-1}(\alpha)$, radius of p-valence of f(z) has been determined.

• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.357-361
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• 1997

We report the operation of a self-starting phase conjugate laser(PCL) oscillator which compensates intracavity phase distortion. The self-starting PCL in the population inverted Nd:YAG gain media produced an output energy of 200 mJ in a 20 ns single-longitudinal-mode pulse at 10Hz. And it showed well-defined Gaussian spatial profile.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.11
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• pp.671-679
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• 2004

This paper presents the on-line current controller tuning method of grid-connected inverter using PSO(particle swarm optimization) technique for minimizing the harmonic current. Synchronous frame PI current regulator is commonly used in most distributed generation. However, due to the source voltage distortion, specially in weak AC power system, current may contain large harmonic components, which increase THD(total harmonic distortion) and deteriorates power quality. Therefore, some tuning method is necessary to improve response of current controller. This paper used the PSO technique to tune the current regulator and through simulation and experiments, usefulness of the tuning method has been verified. Especially in simulating the tuning process, ASM(average switching model) of inverter is used to shorten execution time.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.280-287
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• 2015

Three-level PWM rectifiers applied in medium voltage applications usually operate at low switching frequency to keep the dynamic losses under permitted level. However, low switching frequency brings a heavy cross-coupling between the current components $i_d$ and $i_q$ with a poor dynamic system performance and a harmonic distortion in the grid-connecting current. To overcome these problems, a mathematical model based on complex variables of the three-level voltage source PWM rectifier is firstly established, and the reasons of above issues resulted from low switching frequency have been analyzed using modern control theory. Then, a novel control strategy suitable for the current decoupling control based on the complex variables for $i_d$ and $i_q$ is designed here. The comparisons between this kind of control strategy and the normal PI method have been carried out. MATLAB and experimental results are given in detail.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.91-94
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• 2017

본 연구에서는 Component-Substitution (CS)기반 영상 융합 방법 중 가장 빠른 처리 속도를 보이는 IHS 기법의 분광 왜곡 현상을 해결하기 위하여 히스토그램을 통해 분광 왜곡 현상을 분석하고 평균 필터링을 통해 분광 왜곡 현상을 해결한다. 제안하는 방법의 성능 평가를 위하여 아리랑 3 호로 촬영한 서울 지역 위성 영상에 IHS 방법과 제안하는 방법을 적용하여 주관적으로 비교하고 객관적으로는 Q4, SAM, ERGAS 의 지표를 사용하여 비교한다. 주관적 비교 결과 제안하는 방법이 분광 왜곡을 감소시킴을 보이며, 객관적 비교 결과 IHS 기법 대비 향상된 Q4, SAM, ERGAS 을 보인다.

• Journal of applied mathematics & informatics
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• v.41 no.6
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• pp.1209-1225
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• 2023

In this paper, we defined some new classes of analytic functions in conic domains. We investigate some important properties such as necessary and sufficient conditions, coefficient estimates, convolution results, linear combination, weighted mean, arithmetic mean, radii of starlikeness and distortion for functions in these classes. It is important to mentioned that our results are generalization of number of existing results in the literature.

• Electronics and Telecommunications Trends
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• v.10 no.4 s.38
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• pp.129-142
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• 1995

본 고에서는, 음성을 디지털로 부호화하여 전송함으로써 발생되는 신호 대 양자화왜곡 비(Q)의 개념 및 CODEC과의 관계를 분석하고, MNRU를 디지털 회로로 구현하는데 필요한 입력음성 신호레벨, 잡음의 통계적 성질 및 진폭제한이 음성품질에 미치는 영향을 살펴보았다. 또한, 본 연구에서 구현한 MNRU의 성능에 대해 주관평가 실험을 실시하여, 다른 나라의 주관평가 결과와 비교/분석하였다.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.252-255
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• 1999

A new dead-time compensation method using a disturbance observer is proposed. The dead-time causes the voltage distortion and it can be considered as the disturbance voltage. In this paper, the disturbance voltage is estimated by minimal order observer in the d-q frame and the estimated disturbance voltage is summed with voltage command by a feed-forward. The experiments are carried out for the DSP-based BLDC motor drive system and the results show the effectiveness of the proposed method.

• ETRI Journal
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• v.38 no.1
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• pp.185-194
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• 2016

In this paper, a novel rate control scheme for low delay video coding of High Efficiency Video Coding (HEVC) is proposed. The proposed scheme is developed by considering a new temporal prediction structure of HEVC. In the proposed scheme, the relationship between bit rate and quantization step is exploited firstly to formulate an accurate quadratic rate-quantization (R-Q) model. Secondly, a method of determining the quantization parameters (QPs) for the first frames within a group of pictures is proposed. Thirdly, an accurate frame-level bit allocation method is proposed for HEVC. Finally, based on the proposed R-Q model and the target bit allocated for the frame, the QPs are predicted for coding tree units by using rate-distortion (R-D) optimization. We compare our scheme against that of three other state-of-the-art rate control schemes. Experimental results show that the proposed rate control scheme can increase the Bjøntegaard delta peak signal-to-noise ratio by 0.65 dB and 0.09 dB on average compared with the JCTVC-I0094 and JCTVC-M0036 schemes, respectively, both of which have been implemented in an HEVC test model encoder; furthermore, the proposed scheme achieves a similar R-D performance to Wang's scheme, as well as obtaining the smallest bit rate mismatch error of all the schemes.