• Journal of electromagnetic engineering and science
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• v.2 no.2
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• pp.124-127
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• 2002

A RF tunable bandpass filter using dielectric resonators and varactor diodes is redesigned to improve the passband flatness. Since the tunable liters are generally of narrow bandwidth and the Q value of the varactor diode is usually very low, the passband flatness is strongly deteriorated by sizeable distortion loss. To remedy this problem, we construct modified Chebyshev type filter by use of network synthesis techniques. The key of modified Chebyshev type filter is the rearrangement of the passband poles to improve the passband flatness. To maintain the constant passband bandwidth, design techniques of input/output stage and coupling windows are also applied. Experimental results show that the passband flatness can be improved by purposed method without any additional RF amplitude equalizer.

• Journal of Industrial Technology
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• v.18
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• pp.181-186
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• 1998

The flatness is the most important nature for the surface table. For finding such a flatness, the surface is surveyed along a number of straight lines parallel to the edges of table, which form a grid. Next, the variations in height of the grid points are measured relative to a datum point. If the number of such points is increased. It is not necessarily to use many grid points for finding the original flatness of a measured surface table. So, it is necessary to find the rational quantity of such grid points. It is found that about 220 points per $1m^2$ of surface table for measurement is the rational quantity with less than about 15% error of the original flatness.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.187-193
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• 2003

This paper presents an on-machine measurement method of flatness error fur surface machining processes. There are two kinds of on-machine measurement methods available to measure flatness errors in workpieces: i.e., surface scanning method and sensor scanning method. However, motion errors are often engaged in both methods. This paper proposes an idea to realize a measurement system of flatness errors and its rigorous application for estimation of motion errors of the positioning system. The measurement system is made by modifying the straightness measurement system, which consists of a laser, a CCD camera and processing system, a sensor head, and some optical units. The sensor head is composed of a retroreflector, a ball and ball socket, a linear motion guide unit and adjustable arms. The experimental .results show that the proposed method is useful to identify flatness errors of machined workpieces as well as motion errors of positioning systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.762-768
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• 2003

This paper reports the effects of gain flatness for linearity improvement of feedforward power amplifier fur IMT-2000 band. To investigate the operational characteristics for gain flatness of each amplifier, WCDMA 4FA input signal was used and measured 10 W output power. Especially, linearity improvement for variation of gain flatness of each amplifier was investigated that have an effect on linearity improvement such as delay line, phase, and amplitude imbalances. Variation of gain flatness of main amplifier is 40 MHz and of error amplifier is 40 MHz and 80 MHz bandwidth, respectively. Measured results, gain flatness of main amplifier is less than 1.5 dB and of error amplifier is less than 0.5 dB for more than 20 dB improvement at 5 MHz offset. In addition to that results, the characteristics of feedforward amplifier are drastically varied by gain flatness of error amplifier and it is shown that gain flatness of error amplifier is more important factor for linearity improvement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.105-109
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• 1991

A computer aided flatness calibration system has been developed. Rectangular grids based measurement procedure is proposed with closing error technique. giving advantages over conventional diagonal measurement procedures (‘Union Jack’). A new analysis technique has been developed for flatness evaluation called ‘ETT(Enclose Tilt technique)’, enabling minimum separation definition which is acknowledged as standard term for flatness definition. Practical assessment shows the performance of the developed system.

• Journal of the Korean Mathematical Society
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• v.54 no.2
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• pp.493-506
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• 2017

In this paper, we define the modulus of n-dimensional U-flatness as the determinant of an $(n+1){\times}(n+1)$ matrix. The properties of the modulus are investigated and the relationships between this modulus and other geometric parameters of Banach spaces are studied. Some results on fixed point theory for non-expansive mappings and normal structure in Banach spaces are obtained.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.99-105
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• 1999

The flatness is the most important nature for the surface plates. For finding such a flatnes a surface plate is surveyed along a number of straight lines parallel to the edges of plate which form a grid pattern. Next the variations in height of the grid points are measured relative to a datum point. the relation between the number of such grid points and the flatuness of a measured surface plate is formulated in this study. In addtion it is found that the grid-point-numbers suggested by KS B 5254 and JIS B 7513 have very poor reliability for estimation of flatness incase of the surface plates with poor original flatness.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.11
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• pp.62-69
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• 1992

In this paper, a measurement system of surface flatness test using 2-Bucket algorithm phase-shifting interferometry is designed and constructed. In the conventional surface flatness test system using phase shifting interferometry, it is needed more than 3 fringe datas but we propose 2-Bucket algorithm phase-shifting interferometry which only uses two fringe datas. 2-Bucket algorithm uses the relative phase differences of the neighbour pixels. If we watch the result of phase-shift error test simulation, 2-Bucket algorithm has the same calculating values that 3-Bucket, 4-Bucket and 5-Bucket algorithm have them. Experiments have been carried out on the silicon wafer. The measurement of silicon wafer's surface flatness shows that the flatness topography using 2-Bucket algorithm is similar to that of other algorithms.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.13-16
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• 2005

Many mobile communication systems require bandpass filter with sharp skirt characteristics and consequently a filter was formed by more order. It needs to improve flatness in passband. In this paper, amplitude equalizer was used to improve the flatness of passband. We modified Chebyshev prototype filter by use of network synthesis and computed the prototype elements for Shaping filter. We designed and realized a 13-order combline bandpass filter and 4-order amplitude equalizer with coaxial dielectric resonators at WiBro band. The measured results show $\pm$0.82 dB amplitude difference in passband, 6 dB improved flatness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.20-23
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• 2002

In silicon wafer manufacturing process, the grinding process has been adopted to improve the quality of wafer such as flatness, roughness and so on. This paper describes the effect of grinding process on the surface quality of wafer. The experiments are carried out by high precision in fred grinder with air bearing spindle. The relationship between the inclination of chuck table and the flatness of wafer is investigated, and the effect of grinding conditions including wheel speed, table speed, and feed rate on damage depth and roughness of wafer is also investigated. The experimental results show that there is close relationship between the inclination of the chuck table and the flatness of wafer, and the grinding conditions within this paper little affect the flatness of wafer and relatively high affect the damage depth of wafer.