• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.570-572
• /
• 2008

The modulation quality of the I/Q modulator in a wireless transmitter usually affects system performance and it mostly depends on both a nonlinearity and a distortion, from the third order intermodulation($IM_3$) signal and the error components such as an input amplitude error and a local phase error, respectively. This paper focused on how much the Single Sideband Ratio(SSR), which indicates the signal distortion, changes according to the variation of the error components. Consequently, since a desired signal, side band signal at the I/Q modulator output are also represented with those power series coefficients and the error components, the effects of the error components on SSR to meet the EVM specification of the WPAN can be clearly analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.5A
• /
• pp.363-371
• /
• 2009

OFDM(orthogonal frequency division multiplexing) is very effective forhigh data rate transmission system. However, communication performance becomes worse because of nonlinear distortion resulting from the PAPR. In this paper, we like to propose a tone-controlled CI/OFDM system including the TMD (inter-modulation distortion) reduction method in order to improve the BER performance. In this tone-controlled CI/OFDM system, control tone is additionally inserted in each data symbol of CI/OFDM system to make the CI/OFDM lower the PAPR and robust to nonlinear distortion. So, tone-controlled CI/OFDM using the IMD reduction method shows better BER (bit error rate) performance than methods based on PAPR reduction.

• Journal of Advanced Navigation Technology
• /
• v.23 no.2
• /
• pp.179-185
• /
• 2019

In this paper, we have studied narrow-band analog pre-distortion linearization technique using UHF 400 MHz band 20 W power amplifier. The analog pre-distorter used the SC1894 radio frequency power amplifier linearizer(RFPAL) provided by MAXIM Corp and through the look-up table technique confirmed the intermodulation distortion(IMD) performance and the adjusted channel leakage ratio(ACLR) improvement for bandwidth below 1 MHz which does not operate on existing chips. In the 400 MHz (400 ~ 500 MHz) band, IMD performance and the ACLR improvement of up to 17.46 dB based on 1-channel offset and up to 16.6 dB based on 2-channel offset were confirmed. In the system requiring the same linearity, we confirmed power efficiency improvement of 12.41% at output power of over 40 W.

• 한국HCI학회:학술대회논문집
• /
• 2006.02a
• /
• pp.931-936
• /
• 2006

This paper presents different issues of the real-time compression algorithms without compromising the video quality in the distributed environment. The theme of this research is to manage the critical processing stages (speed, information lost, redundancy, distortion) having better encoded ratio, without the fluctuation of quantization scale by using IP configuration. In this paper, different techniques such as distortion measure with searching method cover the block phenomenon with motion estimation process while passing technique and floating measurement is configured by discrete cosine transform (DCT) to reduce computational complexity which is implemented in this video codec. While delay of bits in encoded buffer side especially in real-time state is being controlled to produce the video with high quality and maintenance a low buffering delay. Our results show the performance accuracy gain with better achievement in all the above processes in an encouraging mode.

• IEIE Transactions on Smart Processing and Computing
• /
• v.4 no.3
• /
• pp.145-148
• /
• 2015

In this letter, we present a new linearization method for a voltage controlled oscillator (VCO)-based quantizer in an analog-to-digital converter (ADC). The nonlinearity of the VCO generates unwanted harmonic spurs and reduces the signal-to-noise and distortion ratio (SNDR) of the VCO-based quantizer. This letter suggests a frequency-to-current feedback method to effectively suppress harmonic distortion. The proposed method decreases the harmonic spurs by more than 53 dB. And a VCO-based quantizer employing the proposed linearization method achieves a high SNDR of 74.1 dB.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2001.11b
• /
• pp.71-76
• /
• 2001

OFDM(Orthogonal Frequency Division Multiplexing)의 단점인 높은 PAPR(Peak-to-Average Power Ratio)을 개선하기 위한 방법 중에서 SDT(Signal Distortion Technique)는 전송시스템의 규격 및 수신기의 변경 없이도 적용 가능한 이점이 있다. 본 논문에서는 SDT에 속하는 clipping과 peak windowing 기법을 Eureka 147 DAB(Digital Audio Broadcasting) 시스템에 적용하여 얻은 BER 및 PSD 성능결과를 토대로 PAPR 개선 정도에 따른 시스템의 요구 $Es/N_0$ 및 out-of-band의 PSD 열화 정도를 분석하였다. Hamming windowing을 적용한 경우, PAPR 4㏈에서 clipping에 비해 요구 $Es/N_0$는 비슷한 열화정도가 나타났으나, out-of-band의 PSD는 5dB 정도 개선되는 성능을 보였다.

• ETRI Journal
• /
• v.38 no.2
• /
• pp.227-234
• /
• 2016

Herein, we demonstrate clipping distortion suppression of directly modulated multi-IF-over-fiber links using a simple shunt diode predistorter. The dynamic range of a directly modulated analog fiber optic link is limited by nonlinear distortions caused by laser-diode clipping. We investigate the link performance in the context of carrie-to-noise and distortion ratio (CNDR) and error vector magnitude (EVM) requirements when supporting LTE-A services. We also design an analog predistorter with a shunt-diode structure, and demonstrate experimentally that the predistorter has the ability to suppress clipping-induced third-order intermodulation distortions of the link by at most 14 dB. It also improves the CNDR and EVM of the 4-IF-multiplexed LTE-A carriers by 7 dB and 2.9%, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.22 no.7
• /
• pp.1515-1522
• /
• 1997

Several image coding algorithms have been developed for the telecommunication and multimedia systems with high image quality and high compression ratio. In order to achieve low entropy and distortion, the system should pay great cost of computation time and memory. In this paper, the uniform cubic lattice is chosen for Lattice Vector Quantization (LVQ) because of its generic simplicity. As a transform coding, the Discrete Wavelet Transform (DWT) is applied to the images because of its multiresolution property. The proposed algorithm is basically composed of the biorthogonal DWT and the uniform cubic LVQ. The multiresolution property of the DWT is actively used to optimize the entropy and the distortion on the basis of the distortion-rate function. The vector codebooks are also designed to be optimal at each subimage which is analyzed by the biorthogonal DWT. For compression efficiency, the vector codebook has different dimension depending on the variance of subimage. The simulation results show that the performance of the proposed coding mdthod is superior to the others in terms of the computation complexity and the PSNR in the range of entropy below 0.25 bpp.

• Proceedings of the KWS Conference
• /
• 2005.06a
• /
• pp.291-293
• /
• 2005

The purpose of this study is to evaluate the effects of line heating variables for forming the curved plate on the behavior of distortion using FEA and experiment. The optimum mixed ratio and standoff for flame heating was established under the heating conditions given in this study. With the heating condition, the predictive equation of angular distortion and transverse shrinkage was established using FEA and verified by comparing the predicted results and experimental results.

• The Journal of Economics, Marketing and Management
• /
• v.3 no.2
• /
• pp.1-8
• /
• 2015

In this paper, the effects of auditor change on audit quality in companies accepted in Tehran stock exchange placed review and we assessed the presence or absence of a significant correlation between them. to assess the quality of data auditing and tax distortions, falsification of accounting estimates, distortion of rules, distortion caused by mistakes in applying accounting policies and other distortions are used as the dependent variable Is. the sample group consisted of 56 companies as experimental group and a control group of 56 other companies a 4-year period, during the years 2011 to 2014 were studied. data needed for research discovery success ratio distortion before and after the change of auditor. To test the research hypotheses paired comparison method is used.