• The Journal of the Acoustical Society of Korea
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• v.26 no.6
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• pp.301-305
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• 2007

In this paper, we propose a simple algorithm for detecting underwater transient signals on the fact that the frequency range of underwater transient signals is similar to audio frequency. For this, we use a preprocessing module of EVRC speech codec that is the standard speech codec of the mobile communications. If a signal is entered into EVRC noise suppression module, we can get some parameters such as the update flag, the energy of each channel, the noise suppressed signal, the energy of input signal, the energy of background noise, and the energy of enhanced signal. Therefore the energy of the enhanced signal that is normalized with the energy of the background noise is compared with the pre-defined detection threshold, and then we can detect the transient signal. And the detection threshold is updated using the previous value in the noisy period. The experimental result shows that the proposed algorithm has $0{\sim}4% error rate in the AWGN or the colored noise environment.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.37-44
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• 2014

This paper proposes a new diagnosis algorithm to detect broken rotor bars (BRBs) faults in induction motors. The proposed algorithm is composed of a frequency signal dimension order (FSDO) estimator and a fault decision module. The FSDO estimator finds a number of fault-related frequencies in the stator current signature. In the fault decision module, the fault diagnostic index from the FSDO estimator is used depending on the load conditions of the induction motors. Experimental results obtained in a 75 kW three-phase squirrel-cage induction motor show that the proposed diagnosis algorithm is capable of detecting BRB faults with an accuracy that is superior to a zoom multiple signal classification (ZMUSIC) and a zoom estimation of signal parameters via rotational invariance techniques (ZESPRIT).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.139-140
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• 2010

This paper presents an indoor prototype for wireless digital signal transmission using Visible Light Communications (VLC) in which high power Light Emitting Diode (LED) is used. Using low cost and off-the-shelf components, the transmitter module is constructed using an AVR Atmega128 microcontroller and commercial white beam LEDs. Modulating the light intensity of the LED enables digital signals to be transmitted across the optical link. The receiver module employs a high speed PIN photodetector for optical signal detection and a recovery circuit for optical-electro signal conversion. By sending digitalized data via VLC technology, many applications can be realized in the areas of consumer advertising, traffic safety information and disaster control.

• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.71-76
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• 2015

In this paper, we developed the hardware GPS signal generator for generating a satellite navigation signal synchronized with Live GPS signal signals and analyzed the performance of signal genterator thorough the experiment For a hardware implementation of the GPS navigation signal synchronous generator, the GPS module may receive a GPS signal in order to generate the same signal as the operation that is transmitted from the current GPS satellite and the synchronized time information and the GPS satellites using the Novatel Inc. OEMStar.In. For generating the GPS synchronization signal, the GPS navigation signal generator was adjusted to a reference clock using the GPS clock synchronous information provided by the GPS receiving module and GPS signals also generated in consideration of the delay of the internal hardware of the generator. In this paper, we analyzed the effect of the receiver via the signal switching between Live GPS signal and generates a signal to measure the performance of the GPS navigation synchronization signal generator. It was confirmed that by the seamless operation of the signal even the moment that the switching of the generated signal from Live GPS signal has occurred through experimentation.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.449-452
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• 2005

For home networking system with a function of air quality monitoring, a wireless sensor module with several air quality monitoring sensors was developed for indoor environment monitoring system in home networking. The module has various enlargements for various kinds of sensors such as humidity sensor, temperature sensor, CO2 sensor, flying dust sensor, and etc. The developed wireless module is very convenient to be installed on the wall of a room or office, and the sensors in the module can be easily replaced due to well designed module structure and RF connection method. To reduce the system cost, only one RF transmission block was used for sensors' signal transmission to 8051 microcontroller board in time sharing method. In this home networking system, various indoor environmental parameters could be monitored in real time from RF wireless sensor module. Indoor vision was transferred to client PC or PDA from surveillance camera installed indoor or desired site. Web server using Oracle DB was used for saving the visions by web-camera and various data from wireless sensor module.

• The Journal of the Korea Contents Association
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• v.6 no.1
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• pp.8-13
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• 2006

In this thesis, an automatic door lock system using a dual tone multiple frequency(DTMF) signal generated as pushing the key button of mobile phone is proposed and implemented. This system consists of a transmitter module and a receiver module for processing the DTMF signal of mobile phone. The DTMF signal of mobile phone connected with ear-phone jack enter into the input terminal of DTMF receiver and those are encoded by a code-converter with 4-bits binary format in the DTMF receiver. The encoded output signals are transmitted to the amplitude shift keying(ASK) modulator of transmitter module and the modulated ASK signals which are converted into radio frequency(RF) signals propagate in a free space. The RF signals passed through a free space are demodulated by the ASK demodulator of receiver module and the demodulated ASK signals are sent to a micro-controller unit(MCU). The output signals processed by the MCU are compared with the secreted identification number which is prerecorded in a microprocessor and are transferred to a power relay. If the result is the same, the automatic door lock system opens a door. In the opposite case, it maintains closing the door. The implemented automatic door lock system operates well in mobile environments.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.2
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• pp.54-60
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• 2018

In this paper, we propose an efficient automatic control method for the collision avoidance of drones. In general, the drones are controlled by transmitting to the flight control (FC) module the received PWM signals transmitted from a RC controller which transduce movements of the knob into PWM signal. We implemented the collision avoidance module in-between receiver and FC module to monitor and change the throttle, pitch and roll control signals to avoid drone collision. In order to avoid the collision, a LiDAR distance sensor and a servo-motor are installed and periodically measure the obstacle distance within -45 degrees from 45 degrees in flight direction. If the collision is predicted, the received PWM signal is changed and transmitted to the FC module to prevent the collision. We applied our proposed method to a hexacopter and the experimental results show that the safety is improved because it can prevent the collision caused by the inadvertency or inexperienced maneuver.

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.4
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• pp.280-288
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• 2009

In this paper, we developed new time information recording module of VSI (VLBI Standard Interface) format by analyzing the Mark5B recorder control and operation software with 1Gbps speed, which is able to record the weak signal of space radio source, through the Korean VLBI Network (KVN). The control and operation software of high-speed recorder consists of 2 kinds of software, which is that it can operate RAID control board by controlling large capacity HDD drive and the network control and operation. Especially, core software in high-speed recorder is able to output the results after performing and analyzing the input command. Through the analysis of control and operation software, new time information recording module, which is needed to process the observed data for correlation, is developed. New developed time information recording module can record the time information together after checking the interrupt of 1PPS(Pulse Per Second) input signal when the observed data will be recorded. To verify the normal operation of the developed time information recording module, we performed the real observation test and confirmed the effectiveness of developed software through analyzing the recorded observation data.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.234-239
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• 2012

This paper presents a compact K-band Doppler radar sensor for human vital signal detection that uses a radar configuration with only single coupler. The proposed radar front-end configuration can reduce the chip size and the additional RF power loss. The radar front-end IC is composed of a Lange coupler, VCO, and single balanced mixer. The oscillation frequency of the VCO is from 27.3 to 27.8 GHz. The phase noise of the VCO is -91.2 dBc/Hz at a 1 MHz offset frequency, and the output power is -4.8 dBm. The conversion gain of the mixer is about 11 dB. The chip size is $0.89{\times}1.47mm^2$. The compact Ka-band Doppler radar system was developed in order to demonstrate remote human vital signal detection. The radar system consists of a Ka-band Doppler radar module with a $2{\times}2$ patch array antenna, baseband signal conditioning block, DAQ system, and signal processing program. The front-end module size is $2.5{\times}2.5cm^2$. The proposed radar sensor can properly capture a human heartbeat and respiration rate at the distance of 50 cm.

• Smart Structures and Systems
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• v.19 no.5
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• pp.499-512
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• 2017

Traditional structural dynamic analysis and Structural Health Monitoring (SHM) of large scale concrete civil structures rely on manufactured embedding transducers to obtain structural dynamic properties. However, the embedding of manufactured transducers is very expensive and low efficiency for signal acquisition. In dynamic structural analysis and SHM areas, piezoelectric transducers are more and more popular due to the advantages like quick response, low cost and adaptability to different sizes. In this paper, the applicable feasibility assessment of the designed "artificial" piezoelectric transducers called Concrete Piezoelectric Smart Module (CPSM) in dynamic structural analysis is performed via three major experiments. Experimental Modal Analysis (EMA) based on Ibrahim Time Domain (ITD) Method is applied to experimentally extract modal parameters. Numerical modal analysis by finite element method (FEM) modeling is also performed for comparison. First ten order modal parameters are identified by EMA using CPSMs, PCBs and FEM modeling. Comparisons are made between CPSMs and PCBs, between FEM and CPSMs extracted modal parameters. Results show that Power Spectral Density by CPSMs and PCBs are similar, CPSMs acquired signal amplitudes can be used to predict concrete compressive strength. Modal parameter (natural frequencies) identified from CPSMs acquired signal and PCBs acquired signal are different in a very small range (~3%), and extracted natural frequencies from CPSMs acquired signal and FEM results are in an allowable small range (~5%) as well. Therefore, CPSMs are applicable for signal acquisition of dynamic responses and can be used in dynamic modal analysis, structural health monitoring and related areas.