• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.2
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• pp.160-169
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• 2007

In this paper, we have described and simulated the effect analysis and correction of phase errors in the SAR rawdata induced by satellite attitude errors such as drift, jitter. This simulation is based on the FSA(Frequency Scaling Algorithm) for high resolution image formation of the Spotlight SAR. Phase errors produce the degradation of SAR image quality such as loss of resolution, geometric distortion, loss of contrast, spurious targets, and decrease in SNR. To resolve this problem, this paper presents method for correction of phase errors using the PGA(Phase Gradient Algorithm) in connection with the FSA. Several results of the phase errors correction are presented for Spotlight SAR rawdata.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.437-443
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• 2008

We have developed an evaluation technique for both ratio error and phase displacement of current transformer (CT) comparator by using the precise standard capacitors and resistors. By applying this technique to equivalent circuit of CT comparator evaluation system, we can obtain the calculated and measured ratio errors (or phase displacements) in the CT comparator. Thus we can evaluate ratio errors and phase displacement of CT comparator by comparing the calculated and measured ratio errors (or phase displacements). The method was applied to CT comparator under test with the ratio errors and phase displacement ranges of $0{\sim}{\pm}10%$ and $0{\sim}{\pm}7.5$ crad, respectively. Finally we have compared the ratio error and phase displacement of the CT comparator obtained in this method with specifications of two companies.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.864-871
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• 2014

In this paper, we propose an optimization method for obtaining beam curve which minimize the phase errors of Rotman lens. This method is based on idea that 3 path lengths from a beam port through equal phase points, which consist of the center point of array antenna and two points placed symmetrically or asymmetrically along array antenna, to the corresponding phase front are equal. According to this method, the optimal locations of beam ports can be obtained directly by finding each equal phase point set on array antenna to minimize the phase errors for each beam direction. Simulation results show that the proposed method is the most optimal and effective method for determining the beam curve of Rotman lens with low phase errors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.7
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• pp.1204-1210
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• 2016

The phase currents must be accurately measured to achieve the instantaneous torque control of AC motors. In general, those are measured using the current sensors. However, the measured current signals can include the offset errors and scaling errors by several components such as current sensors, analog amplifiers, noise filter circuits, and analog-to-digital converters. Therefore, the torque-controlled performance can be deteriorated by the current measurement errors. In this paper we have analyzed the influence caused by vector control of 2-phase induction motor when two errors are included in measured phase currents. Based on analyzed results, the compensation method is proposed without additional hardware. The proposed compensation method was applied vector-controlled inverter for 2-phase induction motor of 360[W] class and verified through computer simulations and experiments.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05b
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• pp.103-108
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• 2010

The purpose of this study is to analyze of the risk factors for oversea plants construction projects. For this study, risk factors data from related literature review, research organization and construction company was researched and classified under each EPC phases. In addition, a questionnaire survey by plant experts was conducted for analysis of risk weight and costs and time impact on each EPC phases. The results of this study are as follows: First, a detail design errors(engineering phase), a equipment procurement plan(procurement phase), and exchange rate fluctuations(construction phase) were analyzed the highest weight factors. Second, a financing plan(engineering phase), quantity take-off bill(procurement phase), and exchange rate fluctuations(construction phase) were analyzed the highest cost impact factors. Third, detail design errors(engineering phase), a equipment procurement plan(procurement phase), and schedule management errors(construction phase) were analyzed the highest time impact factors.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.25-27
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• 2012

The domestic construction industry recognize that review of design and construct-ability has the devastating effects. The way to take advantage of BIM for increase the possibility of discovered the design errors in advance are being discussed a lot recently. Since 2012, Public procurement published that the Turn-key project which is the more than 50 billion won in construction have to let the BIM-based design be mandatory. However, people expected the advent of BIM technology can resolve the existing design errors. But the situation is the connection of design stage and construction stage is very insufficient in domestic. Therefore, in this study understanding the types of design errors in construction phase. according the review of design errors before construction. Then can acceleration the application of BIM to improve the workability in a construction site.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.513-516
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• 2003

Phase Measuring Profilometry(PMP) has been developed as one of three dimensional 3-D shape measuring methods. The 3-D profile of an object was calculated from the phase data obtained by the sinusoidal patterns projected on the object. However, in some cases the approximation includes considerable errors. In this paper, the effect on the errors caused by the optical geometry and the calibration procedure in PMP technique are discussed. The errors which occured in the process of calculating the 3-D profile from the phase distribution are investigated theoritically and experimentally.

• Korean Journal of Optics and Photonics
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• v.22 no.5
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• pp.207-213
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• 2011

We propose a new method to measure the phase errors of an AWG(arrayed waveguide grating) through Monte-Carlo analysis. In the frequency domain method, we used the Monte-Carlo method to fit the theory to the experimental results. The phase and amplitude values are obtained from the fitted theory. To verify our method, we carried out a simulation. Some phase errors were included to make a virtual interferogram and we measured the actual AWG phase errors from it by our method. The results show that our method gives good results if the laser tuning range is larger than 1.7 times of the AWG FSR(free spectral range) and if the phase errors are within ${\pm}50^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1249-1258
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• 2006

Two-dimensional(2-D) radar images, namely, ISAR images from a maneuvering target include unwanted phase errors due to the target's motion. These phase errors make ISAR images to be blurred. The ISAR autofocus technique is required in order to remove these unwanted phase errors. Unless those unwanted phase errors produced by the target's motion are removed prior to target identification, we cannot expect a reliable target identification performance. In this paper, we use the entropy-based ISAR autofocus technique which consists of two steps: range alignment and phase adjustment. We analyze a relationship between the number of sampling point and a image quality in a range alignment algorithm and also analyze a technique for reducing computation time of the SSA(Stage-by-Stage Approachng) algorithm in a phase adjustment.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.10
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• pp.147-154
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• 2000

A new hardware compensation method reducing displacement measurement errors, caused by tilt of index scale in moire linear encoders, has been developed. In conventional moire linear encoders, the detectors are aligned perpendicular to the line of moire fringes this structure is very sensitive to an unwanted tilt of the gratings. In this paper, a newly designed grating, called a phase-modulated grating, is developed to compensate for non-orthogonal errors. By using the phase-modulated grating instead of a conventional index, it is possible to reduce non-orthogonal errors of moire linear encoders.