• ETRI Journal
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• v.30 no.4
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• pp.546-554
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• 2008

Phase-locked loops (PLLs) are among the most important mixed-signal building blocks of modern communication and control circuits, where they are used for frequency and phase synchronization, modulation, and demodulation as well as frequency synthesis. The growing popularity of PLLs has increased the need to test these devices during prototyping and production. The problem of distinguishing and classifying the responses of analog integrated circuits containing catastrophic faults has aroused recent interest. This is because most analog and mixed signal circuits are tested by their functionality, which is both time consuming and expensive. The problem is made more difficult when parametric variations are taken into account. Hence, statistical methods and techniques can be employed to automate fault classification. As a possible solution, we use the back propagation neural network (BPNN) to classify the faults in the designed charge-pump PLL. In order to classify the faults, the BPNN was trained with various training algorithms and their performance for the test structure was analyzed. The proposed method of fault classification gave fault coverage of 99.58%.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.4
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• pp.34-41
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• 2003

A new technique for detecting parametric faults in mixed signal circuits is proposed Pseudo-random sequence from linear feedback shift register(LFSR) is fed to circuit-under-test (CUT) as stimulus and wavelets are used to compact the transient response under this stimulus into a small number of signature. Wavelet based scheme decomposes the transient response into a number of signal in different frequency bands. Each decomposed signal is compacted into a signature using digital integrator. The digital pulses from LFSR, owing to its pseudo-randomness property, are almost uniform in frequency domain, which generates multi-frequency response when passed through CUT. The effectiveness of this technique is demonstrated in our experimental results.

• The Korean Journal of Applied Statistics
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• v.22 no.4
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• pp.759-770
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• 2009

A problem of separating signals from noises is considered, when they are randomly mixed in the observation. It is assumed that the noise follows a Gaussian distribution and the signal follows a Gamma distribution, thus the underlying distribution of an observation will be a mixture of Gaussian and Gamma distributions. The parameters of the mixture model will be estimated from the EM algorithm. Then the signals and noises will be classified by a fixed threshold approach based on multiple testing using positive false discovery rate and Bayes error. The proposed method is applied to a real optical emission spectroscopy data for the quantitative analysis of inclusions. A simulation is carried out to compare the performance with the existing method using 3 sigma rule.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.3 s.309
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• pp.34-42
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• 2006

In general, almost information is stored in only a few wavelet coefficients. This sparse characteristic of wavelet coefficient can be modeled by the mixture of Gaussian probability density function and point mass at zero, and denoising for this prior model is peformed by using Bayesian estimation. In this paper, we propose a method of parameter estimation for denoising using hypothesis-testing problem. Hypothesis-testing problem is applied to variance of wavelet coefficient, and $X^2$-test is used. Simulation results show our method outperforms about 0.3dB higher PSNR(peak signal-to-noise ratio) gains compared to the states-of-art denoising methods when using orthogonal wavelets.

• Toxicological Research
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• v.16 no.4
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• pp.317-323
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• 2000

The immunosuppressive effects of thirty nine chemicals chosen by their potential toxicity were evaluated using a three-step testing method. The immunotoxicity test method developed in this study consisted of three simple assays of lymphoproliferation, mixed leukocyte response, and interleukin (IL)-2 production. The first step was mitogen-induced proliferation assay. Ten chemicals showed the inhibitory effects on the mitogen (lipopolysaccharide or concanavalin A)-induced proliferation in dose-dependent manners. The second step was mixed lymphocyte response. This step crosschecked the growth-suppressive effects detected at the first step. All of 10 chemicals, which showed suppression of lymphoproliferation, also exhibited the suppressive effects on the mixed lymphocyte response in the similar range of chemical concentration. The third step was planned to determine whether or not this growth suppression was mediated through an early activation of T-cell, which could be represented with IL-2 production. Six out of 10 chemicals decreased the interleukin-2 production in the similar concentration range used in the step 1 and 2. These results suggest that those 6 chemicals might have their targets on the signal transduction path-way toward the IL-2 production. In the meantime the other 4 chemicals might have their targets after the IL-2 production signal. Taken all together, the three-step test would be simple, fast, and efficient to deter-mine whether or not the chemical has immunosuppressive effects.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.160-164
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• 2013

A laser ultrasonic inspection system is a non-contact inspection device which generates and measures ultrasonics by using laser beam. A laser ultrasonic inspection system provides a high measurement resolution because the ultrasonic signal generated by a pulse laser beam has a wide-band spectrum and the ultrasonic signal is measured from a small focused spot of a measuring laser beam. In this study, galvanic corrosion phenomenon was measured by non-destructive and non-contact method using the laser. The case of mixed foreign material on the part of corrosion was assumed and laser ultrasonic experiment was conducted. Ultrasonic was generated by pulse laser from the back side of the specimen and ultrasonic signal was acquired from the same location of the front side using continuous wave laser and Confocal Fabry-Perot Interferometer(CFPI). The characteristic of the ultrasonic signal of exist foreign material part was analyzed and the location and size of foreign material was measured.

• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.323-327
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• 2013

A laser ultrasonic inspection system has the advantage of nondestructive testing. It is a non-contact mode using a laser interferometer to measure the vertical displacement of the surface of a material caused by the propagation of ultrasonic signals with the remote ultrasonic generated by laser. After raising the ultrasonic signal with a broadband frequency range using a pulsed laser beam, the laser beam is focused to a small point to measure the ultrasonic signal because it provides an excellent measurement resolution. In this paper, foreign materials are measured by a non-destructive and non-contact method using the laser ultrasonic inspection system. Mixed foreign material on the corroded part is assumed and the laser ultrasonic experiment is conducted. An ultrasonic wave is generated by pulse laser from the back of the specimen and an ultrasonic signal is acquired from the same location of the front side using continuous wave laser and Confocal Fabry-Perot Interferometer (CFPI). The characteristic of the ultrasonic signal of existing foreign material is analyzed and the location and size of foreign material is measured.

• IEMEK Journal of Embedded Systems and Applications
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• v.4 no.1
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• pp.23-28
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• 2009

Testing of analog(and mixed-signal) circuits has been a difficult task for test engineers and effective test techniques to solve these problems are required. This paper develops a new technique which increases fault detection and diagnosis rates for analog circuits by using extended MTSS (Modified Time Slot Specification) technique based on MTSS proposed by the author. High performance current sensors with digital outputs are used as core components for these techniques. A fault diagnosis structure with minimal hardware overhead in ATE is also described.

• Journal of Korea Multimedia Society
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• v.10 no.10
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• pp.1260-1270
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• 2007

Testing and diagnosis of analog circuits(or mixed-signal circuits) continue to be a hard task for test engineers and efficient test methodologies to solve these problems are needed. This paper proposes a novel analog circuits test technique using time slot specification (TSS) based built-in current sensors (BICS). A technique for location of a fault site and separation of fault type based on TSS is also presented. The proposed built-in current sensors and TSS technique has high testability, fault coverage and a capability to diagnose catastrophic faults and parametric faults in analog circuits. In order to reduce time complexity of test point insertion procedure, external output and power nodes are used for test points and the current sensors are implemented in the automatic test equipment(ATE). The digital output of BICS can be easily combined with built-in digital test modules for analog IC test.