• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.83-89
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• 2014

A ku-band complementary cross-coupled differential voltage controlled oscillator is designed, measured and fabricated using $0.18-{\mu}m$ CMOS technology. A 2.4GHz of very wide frequency tuning at oscillating frequency of 14.5GHz is achieved with presented circuit topology and MOS varactors. Measurement results show -1.66dBm output power with 18mA DC current drive from 3.3V power supply. When 5V is applied, the output power is increased to 0.84dBm with 47mA DC current. -74.5dBc/Hz phase noise at 100kHz offset is measured. The die area is $1.02mm{\times}0.66mm$.

• Journal of IKEEE
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• v.23 no.4
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• pp.1440-1447
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• 2019

Currently, the prevalence of autism spectrum disorders in children is reported to be higher and shows various types of disorders. In particular, they are having difficulty in communication due to communication impairment in the area of social communication and need to be improved through training. Thus, this study proposes a method of acquiring voice information through a microphone mounted on a robot designed through preliminary research and using this information to make intelligent motions. An ANN(Artificial Neural Network) was used to classify the speech data into robot motions, and we tried to improve the accuracy by combining the Recurrent Neural Network based on Convolutional Neural Network. The preprocessing of input speech data was analyzed using MFCC(Mel-Frequency Cepstral Coefficient), and the motion of the robot was estimated using various data normalization and neural network optimization techniques. In addition, the designed ANN showed a high accuracy by conducting an experiment comparing the accuracy with the existing architecture and the method of human intervention. In order to design robot motions with higher accuracy in the future and to apply them in the treatment and education environment of children with autism.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.11
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• pp.63-70
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• 2001

We demonstrate the MMIC (monolithic microwave integrated circuit) frequency doublers generating stable and low-cost 29 GHz local oscillator signals from 14.5 GHz input signals. These devices were designed and fabricated by using the M MIC integration process of $0.1\;{\mu}m$ gate-length PHEMTs (pseudomorphic high electron mobility transistors) and passive components. The measurements showed S11 or -9.2 dB at 145 GHz, S22 of -18.6 dG at 29 GHz and a minimum conversion loss of 18.2 dB at 14.5 GHz with an input power or 6 dBm. Fundamental signal of 14.5 GHz were suppressed below 15.2 dBe compared to the second harmonic signal at the output port, and the isolation characteristics of fundamental signal between the input and the output port were maintained above :i0 dB in the frequency range 10.5 GHz to 18.5 GHz. The chip size of the fabricated MMIC frequency doubler is $1.5{\times}2.2\;mm^2$.

• The Journal of the Acoustical Society of Korea
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• v.40 no.6
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• pp.555-565
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• 2021

The goal of this study is to improve flow and noise performances of existing backward-curved blade centrifugal fan system used for circulating cold air in a refrigerator freezer by optimally designing airfoil shape. The unique characteristics of the system is to drive cold airflow with two volute tongues in combination with duct system in a back side of a refrigerator without scroll housing generally used in a typical centrifugal fan system. First, flow and noise performances of existing fan system were evaluated experimentally. A P-Q curve was obtained using a fan performance tester in the flow experiment, and noise spectrum was measured in an anechoic chamber in the noise experiment. Then, flow characteristics were numerically analyzed by solving the three-dimensional unsteady Navier-Stokes equations and noise analysis was performed by solving the Ffowcs Williams and Hawkins equation with input from the flow simulation results. The validity of numerical results was confirmed by comparing them with the measured ones. Based on the verified numerical method, blade inlet and outlet angles were optimized for maximum flow rate using the two-factor central composite design of the response surface method. Finally, the flow and noise performances of a prototype manufactured with the optimum design were experimentally evaluated, which showed the improvement in flow and noise performance.

• Journal of the Korea Society of Computer and Information
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• v.19 no.6
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• pp.93-100
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• 2014

The objective of this study is to propose the measurement system implementation method for the evaluation and measurement of the indoor-impulsive over 170 dB noise source. For the purpose of measuring impulse noise, design and implementation constructed followed subsystems of the testing center, microphone, ear simulator, head and torso simulator and so on. Measurement systems for the accuracy and reliability of impulse noise are implemented when measuring 3 ways of measurements method by the simultaneous measurement system design. For the accuracy and reliability of three mutually indoor-impulse noise measurements were compared, three kinds of measuring methods in accordance with the peak sound pressure level and octave band. Comparing the results of data, the indoor-impulse noise by analyzing a frequency characteristic was validated in difference for the statistical significance. Result are determined by the influence of the reflected wave. Therefore, the flexible size of the interior test site while interior impulse noise measurement system was constructed. Throughout this system can be affected by parameters that are the impulse noise source and the corresponding frequency-characteristic analysis to determine the spectrum of the reflected wave. And, in the near future, indoor impulse noise measurement systems for acquisition and analysis are utilized in useful data.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.8
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• pp.22-26
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• 2012

This paper introduces a 2.5-Gb/s optical receiver implemented in a standard 1P4M 0.18um CMOS technology for the applications of active optical HDMI cables. The optical receiver consists of a differential transimpedance amplifier(TIA), a five-stage differential limiting amplifier(LA), and an output buffer. The TIA exploits the inverter input configuration with a resistive feedback for low noise and power consumption. It is cascaded by an additional differential amplifier and a DC-balanced buffer to facilitate the following LA design. The LA consists of five gain cells, an output buffer, and an offset cancellation circuit. The proposed optical receiver demonstrates $91dB{\Omega}$ transimpedance gain, 1.55 GHz bandwidth even with the large photodiode capacitance of 320 fF, 16 pA/sqrt(Hz) average noise current spectral density within the bandwidth (corresponding to the optical sensitivity of -21.6 dBm for $10^{-12}$ BER), and 40 mW power dissipation from a single 1.8-V supply. Test chips occupy the area of $1.35{\times}2.46mm^2$ including pads. The optically measured eye-diagrams confirms wide and clear eye-openings for 2.5-Gb/s operations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.3
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• pp.207-214
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• 2017

High voltage electric power transmitter GIS(Gas Insulated Switchgear) above 72.5kV needs to satisfy domestic Korean peninsular standard(ES-6110-0002) in KEPCO with respect to normal and special operation conditions which include internal gas pressure, dead weight, wind and seismic load. Some other requirements not described in Korean standard can be applied from other international standards such as IEC(International Electronical Committee) 62271-203 and 62271-207. The GIS is a kind of pressure vessel structure made of aluminum and filled with SF6 gas of internal pressure 0.4~0.5MPa. Finite element analysis of GIS is performed with such operational loads including seismic loading and the stability and reliability is determined according to ASME BPVC(Boiler and Pressure Vessel Code) SEC. VIII standard where the allowable stress level of the pressure vessel is suggested. The result shows that the stress of GIS is satisfied the allowable stress level and the safety factor is about 2.3 for Korean peninsular standard.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.8
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• pp.759-769
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• 2013

Electronic equipment has been applied to virtually every area associated with commercial, industrial, and military applications. Specifically, electronics have been incorporated into avionics components installed in aircraft. This equipment is exposed to dynamic loads such as vibration, shock, and acceleration. Especially, avionics components installed in a helicopter are subjected to simultaneous sine and random base excitations. These are denoted as sine on random vibrations according to MIL-STD-810F, Method 514.5. In the past, isolators have been applied to avionics components to reduce vibration and shock. However, an isolator applied to an avionics component installed in a helicopter can amplify the vibration magnitude, and damage the chassis, circuit card assembly, and the isolator itself via resonance at low-frequency sinusoidal vibrations. The objective of this study is to investigate the dynamic characteristics of an avionics component installed in a helicopter and the structural dynamic modification of its tray plate without an isolator using both a finite element analysis and experiments. The structure is optimized by dynamic loads that are selected by comparing the vibration, shock, and acceleration loads using vibration and shock response spectra. A finite element model(FEM) was constructed using a simplified geometry and valid element types that reflect the dynamic characteristics. The FEM was verified by an experimental modal analysis. Design parameters were extracted and selected to modify the structural dynamics using topology optimization, and design of experiments(DOE). A prototype of a modified model was constructed and its feasibility was evaluated using an FEM and a performance test.