• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2109-2115
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• 2001

Miniaturized specimen technology is useful to characterize the mechanical behavior when it is difficult to sample the material enough for the test. In this study, two kinds of miniaturized Charpy impact specimens(i.e., miniaturized specimen with side groove and without side groove) of aged 1Cr- lMo-0.25V steel were prepared and tested. The relationship between the extent of degradation in terms of ductile brittle transition temperature(DBTT) and the fracture stress of 1Cr-1Mo-0.25V steel was established. The fracture stress obtained from miniaturized specimen without side groove turned out to be linearly related with the DBTT of standard specimen. Therefore the fracture toughness of aged turbine rotor steel might be evaluated by the fracture stress. In addition, the correlation between DBTT of standard specimen and that of miniaturized specimen was investigated. As the results of normalizing DBTT by maximum elastic tensile stress, the normalized DBTT of miniaturized specimen without side groove allows one to estimate that of standard specimen.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.132-137
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• 2001

Miniaturized specimen technology is useful to characterize the mechanical behavior using a minimum volume of material, because it is almost impossible to sample the conventional specimen for the fracture toughness test without damage to equipment. Test material was 1Cr-1Mo-0.25V steel which was widely used for turbine rotor material. Two kinds of miniaturized impact specimens were prepared, i.e., miniaturized specimen with side groove and without side groove. The correlation between ductile brittle transition temperature(DBTT) of full size impact specimen and that of miniaturized impact specimen was made. The characteristics of miniaturized impact specimens technique as well as fracture stress were discussed. Finally, we concluded that the characteristics of fracture stress change on aging time were similar to that of DBTT.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.251-255
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• 2003

In this paper, a miniaturized directional coupler utilizing lumped element is proposed as a interdigital capacitor. The traditional miniaturization technique of transmission line realized a utilizing MIM(Metal-Insulator-Metal) capacitor on CPW(Coplanar Waveguide). However, we present a simplified design procedure without additional manufacturing process utilizing interdigital capacitor on microstrip with ease of design. The similar characteristics between the conventional directional coupler with ${\lambda}/4$ transmission line and the miniaturized directional coupler with ${\lambda}/8$ transmission line are validated through simulation and measurement results. Miniaturization rate of total size is about 25% while coupled line is about 60%. As a result, this proposed directional coupler can reduce the size of mobile communication system at 2 GHz.

• Journal of Navigation and Port Research
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• v.36 no.9
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• pp.737-740
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• 2012

A miniaturized CMOS bandpass filter for a single RF transceiver system is presented, using diagonally end-shorted coupled lines and lumped capacitors. In contrast to conventional miniaturized coupled line filters, it is proven that the effective permittivity variation of the coupled transmission line has no effect on shifting the center frequency when the bandpass filter is highly miniaturized. A bandpass filter at a center frequency of 2 GHz was fabricated by $0.18{\mu}m$ CMOS technology. The insertion loss with the die area of $1500{\mu}m{\times}1000{\mu}m$ is -5.14 dB. Simulated results are well agreed with the easurements. It also verify the center frequency stability in the compact size bandpass filter.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.1
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• pp.144-152
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• 2009

This paper propose highly miniaturized active $90^{\circ}C$ phase difference power divider and combiner for application to wireless communication system. The conventional passive $90^{\circ}C$ power divider and combiner cannot be integrated on MMIC because of their very large circuit size. Therefore, the highly miniaturized active $90^{\circ}C$ phase difference power divider and combiner are required for a development of highly integrated MMIC. In this paper, the highly miniaturized active $90^{\circ}C$ phase difference power divider and combiner employing InGaAs/GaAs HBT were designed, fabricated on GaAs substrate. According to the results, the circuit size of fabricated active $90^{\circ}C$ phase difference power divider and combiner were $1.67{\times}0.87$ mm and $2.42{\times}1.05$ mm, respectively, which were 31.6% and 2.2% of the size of conventional passive branch-line coupler. The output gain division characteristic of proposed divider circuit showed 8.4 dB and 7.9 dB respectively, and output phase difference characteristic showed $-89.3^{\circ}C$. The output gain coupling characteristic of proposed combiner circuit showed 9.4 dB and 10.5 dB respectively, and output phase difference characteristic showed $-92.6^{\circ}C$. The highly miniaturized active $90^{\circ}C$ phase difference power divider and combiner exhibited good RF performances compared with the conventional passive branch-line coupler.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1733-1736
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• 2005

Many studies have been carried out to produce 3D features in the size range between $10{\mu}m\~10,000{\mu}m$, called Meso-scale. If these miniaturized systems have high relative accuracy and good volumetric utilization, it is possible to manufacture more complex and accurate shapes with various materials as well as there are advantages of reducing energy, space and resources. Due to imperfect components and misalignment in assembly, it is necessary to assess the accuracy of the miniaturized system itself to obtain high relative accuracy. Laser interferometers are widely used to measure geometric errors called as quasi-static errors. For miniaturized system, however, it is difficult to install the required accessories such as optics and the measuring range is limited because of the size of the system and also this method is very expensive. Moreover, it is impossible to measure each error component simultaneously. A new system to measure simultaneously multiple geometric errors is proposed using capacitance sensors. Each error was measured using capacitance sensors and a measurement algorithm was mathematically derived. The experiments show that the proposed measurement system can be used effectively to assess the accuracy of miniaturized system at a low cost.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.2
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• pp.129-134
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• 2009

In this paper, we proposed a miniaturized Balun-BPF structure using semi-lumped line The conventional Ring Balun-BPF relatively has a big size structure because they consist of two ring resonators, wide line width ring-resonators for low loss and $\lambda/4$transmission line inverters. The ring resonators are miniaturized to 1/4 size by semi-lumped line and we added triangle patches in the ring resonator for compact Balun-BPF structure. The fabricated Balun-BPF is miniaturized to 1/4 size and contains symmetrical output characteristics of balance ports.

• ETRI Journal
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• v.34 no.1
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• pp.118-121
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• 2012

In this letter, a miniaturized log-periodic dipole array (LPDA) antenna operating from 1 GHz to 6 GHz is proposed for portable direction finding applications. To reduce the lateral size of an LPDA antenna, bow-tie elements and a top-loading technique are utilized and spacing factor is decreased to reduce the spacing between the LPDA elements. The proposed miniaturized LPDA antenna has the measured gain and front-to-back ratio ranging from 1.2 dBi to 3 dBi and from 7 dB to 22 dB, respectively.

• ETRI Journal
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• v.31 no.3
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• pp.315-317
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• 2009

In this letter, a novel antenna with a miniaturized aperture is proposed. The substrate including a split-ring resonator array is inserted into a size-reduced open-ended waveguide. For a low return loss and high radiation efficiency, the ring arrangement is optimized, and a stepped transition using H-plane discontinuity is proposed. The proposed antenna achieves a 70% aperture reduction compared to a conventional standard waveguide antenna of WR-187 (47.6 mm${\times}$22.2 mm). The return loss drops significantly at three frequencies, and a reasonable gain is achieved. The aperture-miniaturized antenna can be used in many antenna applications such as near-field measurement.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.412-416
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• 2005

In this paper we propose low-impedance and miniaturized a wilkinson power divider on MMIC passive component which was fabricated by a novel microstrip line structure employing periodically perforated ground metal (PPGM). The novel microstrip line structure showed much lower impedance and shorter guided-wavelength than conventional one. Using the novel microstrip line with periodically perforated ground metal, a miniaturized 17 ${\Omega}$ power divider was fabricated. The line width of the power divider was 20 ${\mu}m$, and the size of it was 0.110 $mm^2$, which is 21 % of conventional one. The power divider exhibited good RF performances from 10 to 20 GHz.