• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.1 s.343
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• pp.65-70
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• 2006

An image sensor has limited dynamic range while the human eye has logarithmic response over wide range of light intensity. Although the sensor gain can be set high to identify details in darker area on the image, this results in saturation in brighter area. The gamma correction is essential to fit the human eye response. However, the digital gamma correction degrades image quality especially for darker area on the image due to the limited ADC resolution and the dynamic range. This Paper proposes a CMOS image sensor (CIS) with a nonlinear analog-to-digital converter (AU) which performs analog gamma correction. The CIS with the proposed nonlinear analog-to-digital conversion scheme was fabricated with a $0.35{\mu}m$ CMOS process. The analog gamma correction using the proposed nonlinear ADC CIS provides the 2.2dB peak-signal-to-noise-ratio(PSM) improved image qualify than conventional digital gamma correction. The PSNR of the image obtain from the digital gamma correction is 25.6dB while it is 27.8dB for analog gamma correction. The PSNR improvement over digital gamma correction is about $28.8\%$.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.882-885
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• 2003

In this paper, nonlinear echo cancellation using a correlation LMS (CLMS) algorithm is proposed to cancel the undesired nonlinear echo signals generated in the hybrid system of the telephone network. In the telephone network, the echo signals may result the degradation of the network performance. Furthermore, digital to analog converter (DAC) and analog to digital converter (ADC) may be the source of the nonlinear distortion in the hybrid system. The adaptive filtering technique based on the nonlinear Volterra filter has been the general technique to cancel such a nonlinear echo signals in the telephone network. But in the presence of the double-talk situation, the error signal for tap adaptations will be greatly larger, and the near-end signal can cause any fluctuation of tap coefficients, and they may diverge greatly. To solve a such problem, the correlation LMS (CLMS) algorithm can be applied as the nonlinear adaptive echo cancellation algorithm. The CLMS algorithm utilizes the fact that the far-end signal is not correlated with a near-end signal. Accordingly, the residual error for the tap adaptation is relatively small, when compared to that of the conventional normalized LMS algorithm. To demonstrate the performance of the proposed algorithm, the DAC of hybrid system of the telephone network is considered. The simulation results show that the proposed algorithm can cancel the nonlinear echo signals effectively and show robustness under the double-talk situations.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.220-228
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• 1995

An optimized 4-stage 12-bit pipelined CMOS analog-to-digital converter (ADC) architecture is proposed to obtain high linearity and high yield. The ADC based on a multiplying digital-to-analog converter (MDAC) selectively employs a binary-weighted-capacitor (BWC) array in the front-end stage and a unit-capacitor (UC) array in the back-end stages to improve integral nonlinearity (INL) and differential nonlinearity (DNL) simultaneously whil maintaining high yield. A digital-domain nonlinear error calibration technique is applied in the first stage of the ADC to improve its accuracy to 12-bit level. The largest DNL error in the mid-point code of the ADC is reduced by avoiding a code-error symmetry observed in a conventional digitally calibrated ADC is reduced by avoiding a code-error symmetry observed in a conventional digitally calibrated ADC is simulated to prove the effectiveness of the proposed ADC architecture.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.10-17
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• 1995

this thesis proposes a new echo canceller that can be used in a fulll-duplex digital subscriber loopmodem. The modem suffers from nonlinear distortion such as transmitted pulse asymmetry, saturation in transformers, and nonlinearity of data converters. The proposed nonlinear echo canceller can compensate the nolinear distortion by using a nonlinear digital filter based on canonical pieceewise-linear (CPWL) function. Numerical results based on computer simulation are given in this paper. It is shown that the convergence characteristics depend on the initial values of weights of linear filters with absoluters and that the nonlinearity in digital-to-analog(D/A) converter can be compensated by a relatively small number linear filters with absoluters. It is also shown that the proposed algorithm has a faster convergence rate in comparison with Voterra algorithm.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.5
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• pp.713-718
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• 2016

Predicting precise specifications of differential mixed-signal circuits is a difficult problem, because analytically derived correlation between process variations and conventional specifications exhibits the limited prediction accuracy due to the phase unbalance, for most self-tests. This paper proposes an efficient prediction technique to provide accurate specifications of differential mixed-signal circuits in a system-on-chip (SoC) based on a nonlinear statistical nonlinear regression technique. A spectrally pure sinusoidal signal is applied to a differential DUT, and its output is fed into another differential DUT through a weighting circuitry in the loopback configuration. The weighting circuitry, which is employed from the previous work [3], efficiently produces different weights on the harmonics of the loopback responses, i.e., the signatures. The correlation models, which map the signatures to the conventional specifications, are built based on the statistical nonlinear regression technique, in order to predict accurate nonlinearities of individual DUTs. In production testing, once the efficient signatures are measured, and plugged into the obtained correlation models, the harmonic coefficients of DUTs are readily identified. This work provides a practical test solution to overcome the serious test issue of differential mixed-signal circuits; the low accuracy of analytically derived model is much lower by the errors from the unbalance. Hardware measurement results showed less than 1.0 dB of the prediction error, validating that this approach can be used as production test.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.351-358
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• 2013

We propose a correction method of nonlinear frequency sweep in an FMCW(Frequency Modulated Continuous Wave) laser range finder. FMCW laser range finder requires linear frequency sweep for high resolution, and nonlinear frequency sweep makes the system performance degrade. In general, VCO(Voltage Controlled Oscillator) which is a component used for frequency modulation in FMCW method has nonlinear property. To correct the nonlinear frequency sweep, we utilize an auxiliary delay structure for generating trigger signal of ADC(Analog to Digital Converter). Because the trigger signal has same rate of change with the beat signal, the nonlinearity of the beat signal can be corrected. the experimental results show that the proposed method effectively eliminates the nonlinear frequency sweep problem and enhances the system performance.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.199-202
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• 1996

In this paper, we used the maximum likelihood method for 2-point aerodynamic model to determine the parameters of the ChangGong-91. Since the estimation from the flight test of real aircraft is the most reliable, we performed the flight test of ChangGong-91 to get the parameters such as velocity, height, 3 axis acceleration, 3 axis angular rate, pitch angle, angle of attack, temperature and so on. We recorded the flight test data in S-VHS tapes and stored them to personal computer using A/D(analog to digital) converter. Flight test was done in stall motion, and the acquired data was be processed with parameter identification method.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.4
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• pp.249-254
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• 2013

A fast multiplier and ADC are essential to process the analog signals in real time. The double-base number system(DBNS) is known as an efficient method for this purpose. The DBNS uses the numbers 2 and 3 as the base numbers simultaneously. The system has an advantage of fast multiplication, less chip area, and low power consumption compared to the binary multiplier. However, the inherent errors of the log number's intrinsic tolerance in DBNS are accumulated in a FIR digital filter, so the signal-to-noise ratio(SNR) has a tendency to be degraded. In this paper, the nonlinear encoder of ADC is designed to compensate the accumulated errors of DBNS by analysing the error distributions of various filter coefficients. The new ADC does not sacrifice its own advantages because the encoder circuits are modified only. The experiments were done with an FIR filters those were designed to have -70dB of SNR in stop band. The proposed nonlinear ADC encoder could drop the SNR to -45dB in stop band, in contrast to -35dB with the linear encoder.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.52-59
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• 2009

In modern radars, dynamic range requirements far severed due to high CNR(Clutter-to-Noise Ratio) environment operation scenario. ADC spurious signal restricted the required dynamic range. In this paper, receiver gain of active phased array radar dependent on ADC nonlinear characteristic was analyzed. Within limited scope of ADC SFDR which blocks required system dynamic range, ADC dynamic range reaches trade-off with ADC SNR loss. Comparing antenna stage output noise voltage to that of ADC input, receiver gain was mathematically analyzed. Finally the whole contents were explained from the application example.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.78-84
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• 2012

In this paper, we introduced the design technique about a Ka band receive module for millimeter wave seekers. The receiver module consists of a waveguide, circulator and transition for antenna connection, and a limiter and gain control amplifier for receiver protection. This module is comprised of a sum, azimuth and elevation channel for receiving monopules signal, and a SLB channel for the acquisition of jamming signal. In this paper, receiver gain and range of gain control dependent on ADC nonlinear characteristic was analyzed and designed for wide dynamic range receive. In the test result of the fabricated Ka-band receive, the frequency band is 1 GHz, the noise figure is as low as 8.2 dB, the gain is $56{\pm}2dB$, the dynamic range is 135 dB, the gain congtrol is more than 86 dB, the channel isolation is more than 35 dB.