• Korean Journal of Optics and Photonics
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• v.21 no.4
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• pp.175-178
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• 2010

A transmission type color filter based on a thin film Ag-$SiO_2$-Ag etalon was proposed and realized in a quartz substrate. The device could acquire infrared suppressed transmission and wide effective area compared to costly e-beam lithography and laser interference lithography. The FDTD method was introduced to take into account the effect of the dispersion characteristics of the silver metal and the thickness thereof. Three different color filters were devised: The cavity length for the red, green and blue filters were 160 nm, 130 nm, and 100 nm respectively, with the metal layer unchanged at 25 nm. The observed center wavelengths were measured at 650 nm, 555 nm, and 480 nm for the red, green, and blue devices; the corresponding bandwidths were about 120 nm, 100 nm, and 120 nm; and the peak transmission for all was ~60%. Finally the relative transmission was measured to decline with the angle of the incident beam with the rate of 1%/degree.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.5 s.311
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• pp.62-71
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• 2006

Development of an artificial reverberation algorithm with low memory requirements has been an issue of importance in applications such as mobile multimedia devices. One possible solution to this problem is to embed a time-varying all-pass filter to the feedback loop of the comb filter. In this paper, theoretical and perceptual analyses of reverberators embedding time-varying all-pass filters are presented. The analyses are to iud a perceptually acceptable degree of phase variation by the all-pass filter. Based on the analyses, we propose a new methodology of designing reverberators embedding time-varying all-pass filters. Through the subjective tests, we showed that, even with smaller memory, the proposed method is capable of providing perceptually comparable sound quality to the conventional methods involving time-invariant parameters.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.2
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• pp.106-111
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• 2015

Since most reference voltage generator circuits have bi-stable characteristics, it is important to employ a proper start-up circuit to operate a reference generator in the desired state. In this paper, we propose a start-up circuit for a low voltage reference generator. This start-up circuit determines the state of the circuit reliably by measuring the current drawn by BJTs in the circuit, which is well-defined in the desired state. To measure the current using CMOS-compatible devices only, a comparator with an internal offset voltage is used. The reliability of the proposed circuit is confirmed by Monte-Carlo simulations of the start-up operation, which show that, with the proposed start-up circuit, the low voltage reference generator starts reliably with supply voltages over 850mV even in the presence of device mismatches.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.2
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• pp.91-97
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• 2013

Self-heating effects during operation of high current AlGaN/GaN power transistors degrade the current-voltage characteristics. In particular, this problem becomes serious when a low thermal conductivity Si substrate is used. In this work, AlGaN/GaN-on-Si devices were fabricated with various channel widths and Si substrate thicknesses in which the structure dependent self-heating effects were investigated by temperature dependent measurements as well as thermal simulation. Accordingly, a device structure that can effectively dissipate the heat was proposed in order to achieve the maximum current in a multi-channel, large area device. Employing via-holes and common electrodes with a 100 ${\mu}m$ Si substrate thickness improved the current level by 75% reducing the channel temperature by 68%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.33-41
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• 2017

This paper suggests a hand gesture recognition technology to control smart devices using multiple Doppler radars and a support vector machine(SVM), which is one of the machine learning algorithms. Whereas single Doppler radar can recognize only simple hand gestures, multiple Doppler radar can recognize various and complex hand gestures by using various Doppler patterns as a function of time and each device. In addition, machine learning technology can enhance recognition accuracy. In order to determine the feasibility of the suggested technology, we implemented a test-bed using two Doppler radars, NI DAQ USB-6008, and MATLAB. Using this test-bed, we can successfully classify four hand gestures, which are Push, Pull, Right Slide, and Left Slide. Applying SVM machine learning algorithm, it was confirmed the high accuracy of the hand gesture recognition.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.5
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• pp.430-433
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• 2017

This paper presents a S/C/X-band LNA MMIC with resistive feedback structure in 0.25 um GaN HEMT process. The GaN devices have advantages as a high output power device having high breakdown voltage, energy band gap and stability at high temperature. Since the receiver using the GaN device with high linearity can be implemented without a limiter, the noise figure of the receiver can be improved and the size of receiver module can be reduced. The proposed GaN LNA MMIC based on 0.25 um GaN HEMT device is achieved the gain of > 15 dB, the noise figure of < 3 dB, the input return loss of > 13 dB, and the output return loss of > 8 dB in the S/C/X-band. The current consumption of GaN LNA MMIC is 70 mA with the drain voltage 20 V and the gate voltage -3 V.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.12
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• pp.974-981
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• 2017

Globally, owing to the rapid expansion of radio stations overseas, the frequency coordination system is managed as a preconditioning system. As a result, it is predicted that many types of radio stations will be established for domestic purposes, such as 5G, low-power IoT devices with long distance, based on licenses and non-license in the future. Many problems such as unnecessary launching of radio resources and spectrum-sharing technology exist, and it is necessary to consider the introduction of the abovementioned system and other plan system. In this paper, we explore the outline of radio station licensing and introduce the contents of the survey on another industry licensing. The plans were studied by discussing problems that may occur in future, through comparative analysis of radio stations and other industry licensing. Moreover, the differences were compared and analyzed using graphs. Finally, we discussed the problems convergence products such as drone may offer in the future.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.3
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• pp.341-347
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• 2015

This study aims to design a chief VDR(Voyage Data Recorder) system which is appropriate to small and medium sized vessels and also implement the data about marine communication devices, sensors, etc. to be stored or printed at the navigator when those data are connected to VDR through data communication between marine navigation and VDR which are based on serial communication or internet in order to prove efficiency of the marine navigator. Also, the design of VDR is intended to be small and light in order to expand to apply it to small and medium vessels, which enables to analyze causes of marine accidents precisely through its characteristic functions which are the same as those at "vehicle mounted black-box" (location of the car, image and voice storage) by which the same roles are played on land.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.3
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• pp.671-677
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• 2012

A black-box program was implemented in order to monitor abnormal symptoms of human body irregularly occurring during sleep. The system consists of sensor probing body signals, auxiliary devices such as the alarm, lamp, network camera, and signal monitoring computer. Various types of sensors, PPG, ECG, EEG, temperature, respiration sensor, G-sensor, and microphone were used to more exactly identify the causes of abnormal symptoms. If a symptom occurs, the system records the patient's condition to provide information being utilized in the treatment. The sensors are attached on some locations of body being proper to check a specific type of abnormal reaction. Based on the normal range and type of measurement data, criteria of signal levels were set to distinguish abnormal reaction. An abnormal signal being probed, the program starts to operate the lamp, alarm, and network camera at the same time and stores the signal and video data.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.256-261
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• 2011

In this paper, a design and an implementation of an Analog to Digital (A/D) converter are introduced for the conversion of monitored battery cell voltage in the cell voltage monitoring(CVM) system in battery management system(BMS), which is one of the key devices of ECO hybrid cars. The A/D converter in CVM system required a middle conversion speed and a high resolution, therefore, a successive approximate register(SAR) typed A/D converter with 10 bits resolution has been designed and implemented using Magna 0.6um 40V process. The measurement result which kept ${\pm}1$ LSB accuracy in the full scale range(FSR) of 5V, showed the usefulness of the SAR typed A/D converter in realizing a CVM system.