• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.196-201
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• 2003

Axial fans are widely used for automotive engine cooling device due to their ability to produce high flow rate to keep engine cool. At the same time, the noise generated by these fans causes one of the most serious problems. Especially, engine cooling fan noise in idle condition of a car is noticeable. Therefore, the high efficient and low-noise fan is seriously needed. When a new fan system is designed, system resistance and non-uniform inflow are the key factors to get the high performance and low noise fan system. In this study, experimental study on the fan and system was carried out and brought a successful result of performance and noise from a designed fan. And through the modification of the fan system, the fan produced more flow rate and became less noisy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.796-805
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• 2000

A 30GHz band low noise amplifier module, which has linear gain of 30dB and noise figure of 2.6dB, for 30GHz satellite communication transponder was developed by use of MMIC and thin film MIC technologies. Two kinds of MMIC circuits were used for the low noise amplifier module, the first one is ultra low noise MMIC circuit and the other is wideband and high gain MMIC circuit. The pHEMT technology with 0.15$mu extrm{m}$ of gate length was applied for MMIC fabrication. Thin film microstrip lines on alumina substrate were used to interconnect two MMIC chips, and the thick film bias circuit board were developed to provide the stabilized DC bias. The input interface of the low noise amplifier module was designed with waveguide type to receive the signal from antenna directly, and the output port was adopted with K-type coaxial connector for interface with the frequency converter module behind the low noise amplifier module. Space qualified manufacturing processes were applied to manufacture and assemble the low noise amplifier module, and space qualification level of environment tests including thermal and vibration test were performed for it. The developed low noise amplifier was measured to show 30dB of minimum gain, $\pm$0.3dB of gain flatness, and 2.6dB of maximum noise figure over the desired operating frequency range from 30 to 31 GHz.

• Journal of KSNVE
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• v.7 no.4
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• pp.689-700
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• 1997

There are many difficulties in designing the engine structure properly due to the strong conflicts between NVH characteristics and the high performance, light weight and low product cost. Many feasible noise reduction techniques should be carefully incorporated to meet such stringent noise requirements. It is also required that the engine development be carried out by introducing concurrent engineering, in which the analysis and test database are usefully applied to the detail designs from the 1st stage. This paper reviews the significance of the noise characteristics of the structure elements in relation to the combustion pressure. The mechanisms of the crank shaft rumbling, which is the main source having the bad influence on the sound quality, are also explained. The influences of dynamic behavior of engine structure on its noise are investigated, followed by discussions on experimental results of the features necessary for the design of low noise engine concepts.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.394-402
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• 2009

To investigate the heavy-weight impact noise of apartment houses, numerical analysis was performed. The analysis acoustic pressure consider acoustic mode by finite element method. The variables considered effecting on the acoustic pressure are the Acoustic mode, acoustic damping, and the impulse load. The heavy-weight impact noise is a changeable value in the room. Since the most part of the frequency component of heavy-weight impact noise has low frequency. The noise in low frequency is related to the vibration of structure, the reflection of acoustic wave caused by wall and the standing wave called by acoustic mode. The prediction by the numerical analysis was verified with test result of the heavy weight-impact noise at apartment houses.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.1-7
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• 2007

In this paper, two kinds of initial oxidation methods i.e., SLTO(Slow Low Temperature Oxidation: $700^{\circ}C$) and RTO(Rapid Thermal Oxidation: $850^{\circ}C$) are applied prior to the plasma nitridation for ultra thin oxide of RPNO (Remote Plasma Nitrided Oxide). It is observed that SLTO has superior characteristics to RTO such as lower SS(Sub-threshold Slope) and improved Ion-Ioff characteristics. Low frequency noise characteristics of SLTO also showed better than RTO both in linear and saturation regime. It is shown that flicker noise is dominated by carrier number fluctuation in the channel region. Therefore, SLTO is promising for nano-scale CMOS technology with ultra thin gate oxide.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.8
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• pp.124-129
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• 2009

Recently, there has been a growing global interest in environmental conservation, and the field of electric power equipment has been working to become more environment-friendly. Accordingly the 154[kV] low noise transformer is developed through the research. The low noise transformer decreases the audible noise level but the low noise transformer has several changes in the increase of weight and volume and the application of rubber damper. Therefore it is necessary to inspect the test, transportation, installation and operation about field application. In this paper, we investigate the standards of the audible noise level, the weight and volume of the transportation, the installation space and operation in order for effective field application.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.131-133
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• 2000

Single phase simulations were carried out in order to determine a solutive conductor to the aeolian noise which will be locally applied to 765 kV transmission lines Basic solutive conductors have already been proposed including conductors equipped with spiral rod. low noise conductor of a special shape and others. A low aeolian noise conductor, however, should have excellent corona characteristics in addition to aeolian noise reduction function. In this paper, we compared the performances of the audible noises and radio interferences of 6 candidate conductor bundles by using corona cage. We also developed two programs to need for evaluating environmental effects of each conductor bundle. Those are a program to calculate the conductor surface gradient of various special bundles and a conversion program of single phase data to the model of transmission line. The future determination on the final low aeolian noise conductor will be made through a long-term test to verify environmental impacts at the full-scale Kochang 765 kV test line.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.8
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• pp.1297-1304
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• 2002

The phase locked oscillator having a low phase noise and high output in Ku-band was designed. To obtain the low phase noise and high output characteristics of oscillator, the nonlinear equivalent circuits of p-HEMT was analyzed by TOM method and we have decided the trade-off bias point between the low phase noise and the output power of oscillator. The designed phase locked oscillator with prescaler for stable operation, experiment results exhibits output power of 1003m with phase noise in the phase locked state of -824BC/HB at 10mz offset from 13.250Hz, and simulation result of 1003m output power in the phase noise -840Bc/Hz at 10KHz offset frequency respectively. a good agreement has been obtained between simulations and experiments results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.462-469
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• 2001

In this paper, local oscillator in K band using low frequency noise upconversion gain anaylsis was designed and measured. We extended Two Signal Method(TSM) to estimate upconversion gain and resulting phase noise. To confirm the validity of the proposed method, a free-running oscillator which had low upconversion gain was designed. The measured oscillation frequency was 23.42 GHz and phase noise at 1 MHz of offset was -105.2 dBc/Hz. Also, this oscillator was operated for subharmonic injection locked osci1lator(SILO). In this case, SILO showed ideal frequency multiplier phase noise characteristics at low subharmonic injection power level.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1599-1600
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• 2006

In this paper, a small size, $7{\times}6\;mm^2$, Low Noise Amplifier(LNA) using LTCC process was fabricated with multi-layer structure for 2.4GHz wireless LAN. The measured results demonstrate that the bandwidth is 130 MHz, and the operating frequency is from 2.39GHz to 2.52GHz. The power gain is above 7.3 dB in the operating frequency range and the gain flatness is 0.5 dB. The maximum S11 is -4 dB and the maximum S22 is -7.5 dB. The noise figure is less than 1.83 dB. The measured power gain, S11 and S22 were had poorer performance than the simulation results. The reason for this discrepancy is that the input and output matching was not performed exactly. However, the noise figure of the LTCC low noise amplifier is better than simulation result. It is found that it is possible to fabricate a LTCC low noise amplifier in a small size.