• 한국통신학회논문지
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• 제31권2C호
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• pp.191-199
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• 2006

본 논문에서는 OFDM 신호의 높은 PAPR과 전력 증폭기의 비선형성에 의한 신호의 왜곡과 스펙트럼의 확산을 방지하기 위하여 $rho$차 역필터 구조를 사용하는 전치 보상기를 구현하는 방안을 제시한다. 메모리가 없는 고전력 증폭기를 다항식으로 모델링 하고 전치 보상기로써 비선형 증폭기 특성의 역모델인 $rho$차 역필터 구조를 이용한다. $rho$차 역필터 구조는 비선형 시스템이 다항식으로 모델링 된다면 다항식의 계수만으로 구현될 수 있으므로 많은 메모리가 필요 없다. 비선형 전력 증폭기 모델의 계수 갱신을 위하여는 LMS, RLS 알고리듬을 모두 사용할 수 있으며 계수의 개수가 적어 수렴 속도가 빠르고 복소 계산이 필요 없으므로 계산도 간단하다.

• 한국음향학회지
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• 제23권4호
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• pp.333-339
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• 2004

본 논문에서는 벡터 양자화기와 피라미드 벡터 양자화기를 직렬로 결합하여 16차 벡터 소스에 대한 vector quantizer-pyramid vector quantizer (VQ-PVQ)를 개발하였으며, 예측 구조와 세이프티-넷 (safety-net) 개념을 결합시켜 광대역 음성 부호화기용 LPC 계수 양자화 기를 설계하였다. 본 양자화기의 성능은 AMR-WB(ITRT-T G.722.2)의 LPC양자화기 성능과 비교하였는데, 스펙트럼 왜곡 및 메모리 요구량에서 상당한 이득을 얻었다.

• ETRI Journal
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• 제23권1호
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• pp.16-22
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• 2001

Efficient quantization methods of the line spectrum pairs (LSP) which have good performances, low complexity and memory are proposed. The adaptive quantization range method utilizing the ordering property of LSP parameters is used in a scalar quantizer and a vector-scalar hybrid quantizer. As the maximum quantization range of each LSP parameter is varied adaptively on the quantized value of the previous order's LSP parameter, efficient quantization methods can be obtained. The proposed scalar quantization algorithm needs 31 bits/frame, which is 3 bits less per frame than in the conventional scalar quantization method with interframe prediction to maintain the transparent quality of speech. The improved vector-scalar quantizer achieves an average spectral distortion of 1 dB using 26 bits/frame. The performances of proposed quantization methods are also evaluated in the transmission errors.

• 전기학회논문지
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• 제60권5호
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• pp.1023-1029
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• 2011

In the industrial vision systems, image correction has great influence on the overall performance of measurement or inspection. The overall area of distorted image is usually splitted into small control areas, and each area is corrected by its control points. The performance of correction methods using control points can be improved by reduction of control areas because the computational time and memory highly depend on the number of control areas. We develop a merging algorithm that reduces control areas and preserves the correction accuracy. The algorithm merges the splitted control areas by use of quad tree method. Experimental results are presented to verify the usefulness of the proposed method.

• 전자공학회논문지S
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• 제34S권4호
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• pp.50-56
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• 1997

In this paper, efficient quantization methods of line spectrum pairs (LSP) which has good performances and low complexity and memory are proosed for vocoder of mobile communication system. The adaptive quantization method utilizing the ordering property of LSP parameters is used in a scalar quantizer and a vector-scalar hybrid quantizer. The proposed scalar quantization algorithm needs 31 bits/frame to maintain the transparent quality of speech. The improved vector-scalar quantizer achieves an average spectral distortion of 1dB using 26 bits/frame. The proposed methods are evaluated in the channel errors and changed the predictor structure to maintain the robustness to channel errors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.11-14
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• 1990

The Complex Harmonic Balance Finite Element Method CHBFEM ) is dicussed for the time - periodic magnetic field with saturation characteristics. And Jw - method which is used for analyzing liner system with sinusoidal voltage input can be generalized in nonlinear time-periodic magnetio field system. The CHBFEM enables us to calculate the each harmonic magnetic flux ditribution and the distortion of currents resulting from material at an AC voltage source and to save calculating time, the number of calculation and computer memory.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.276-279
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• 2005

The proposed Novel OverDriving Technology with Optimum Look-up-Table（LUT）is suggested to be a better solution to reducing the occurrence of overshooting caused by the traditional overdriving method implemented to normally liquid crystal (VA mode). Chunghwa Picture Tubes, LTD. (CPT) has successfully implement this tech into 20 inch TFTLCD TV module at the present day. The proposed technology can speed up gray-to-gray response time of LCD less than one half of frame time. On the side, Optimum LUT construction apply the compression scheme to record total actual grayscale transfer characteristics instead of applying the normal spread method such as linear / non-linear interpolation. The memory space is been reduced and the distortion of the image quality is lesser.

• Journal of electromagnetic engineering and science
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• 제8권1호
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• pp.17-22
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• 2008

It is presented that sampling rates for behavioral modeling of quasi-memory less nonlinear devices can be far less than the Nyquist rate of the input signal. Although it has been believed that the sampling rate of nonlinear device modeling should be at least the Nyquist rate of the output signal, this paper suggests that far less than the Nyquist rate of the input signal can be applied to the modeling of quasi-memoryless nonlinear devices, such as frequency multipliers. To verify, a QPSK signal at 820 MHz were applied to a frequency tripler, whereby the device can be utilized as an up-converting mixer into 2.46 GHz with the aid of digital predistortion. AM-AM, AM-PM and PM-PM can be successfully measured regardless of sampling rates.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.1098-1103
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• 1994

In this paper, we design and implement the Korean speech synthesis by rule system. This system is applied the multiband excitation signal on voiced sounds. The multiband excitation signal is obtained by mixing impluse spectrum and which noise spectrum. We find that the quality of synthesized speech is improved using this application. Also, we classify the voiced sounds by cepstral euclidian distance measure for reducing overhead memory. The representative excitation signal of the same group's voiced sounds is used as excitation signal on synthesis. This method does not affect the quality of synthesized speech. As the result of experiment, this method eliminates the "buzziness" of synthesized speech and reduces the spectral distortion of synthesized speech.ed speech.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.673-676
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• 2015

디지털 전치 왜곡기법은 비선형 전력증폭기의 역함수에 해당하는 디지털 전치왜곡 특성을 찾아 송신신호를 미리 왜곡 시켜줌으로써 비선형 전력증폭기를 선형화시키는 기술이다. 일반적으로 전력증폭기는 시간과 전력 그리고 온도에 따라 비선형 특성이 변하기 때문에 디지털 전치왜곡기법에서는 송신신호와 되먹임 신호를 주기적으로 메모리(RAM)에 저장하여 전력증폭기 특성 함수의 역함수인 전치 왜곡 계수를 찾게 된다. 하지만 적응형 알고리즘이 원하는 전치왜곡 계수에 수렴하기 위해서는 긴 샘플이 요구되는데 이는 많은 메모리를 요구한다. 본 논문에서는 전치왜곡 엔진부에서 짧은 길이의 메모리를 사용하지만 이 메모리의 샘플을 재활용하여 반복 연산 수행을 통해 긴 용량의 메모리를 이용하여 구현하였을 경우와 유사한 성능을 얻는 방법을 제안하며 이를 컴퓨터 모의실험을 통해 성능 비교 분석한다.