• Journal of Digital Convergence
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• v.12 no.6
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• pp.271-276
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• 2014

In a speech coding system using excitation source of voiced and unvoiced, it would be involved a distortion of speech quality in case coexist with a voiced and unvoiced consonants in a frame. In this paper, I propose a method of 8kbps Multi-Pulse Speech Coding(FBD-MPC: Frequency Band Division MPC) by using TSIUVC(Transition Segment Including Unvoiced Consonant) searching, extraction and approximation-synthesis method in a frequency domain. I evaluate the 8kbps MPC and FBD-MPC. As a result, SNRseg of FBD-MPC was improved 0.5dB for female voice and 0.2dB for male voice respectively. Compared to the MPC, SNRseg of FBD-MPC has been improved that I was able to control the distortion of the speech waveform finally. And so, I expect to be able to this method for cellular phone and smart phone using excitation source of low bit rate.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.125-128
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• 2008

In this paper, a stand-type planar antenna of 900MHz RFID band is designed and fabricated. As the proposed antenna is stand-type use of air permittivity, Bandwidth used ground height at rectangle patch structure and coaxial feed line is widen. Also wideband width can solve problem that RFID tag attached to things happens frequency shift keying phenomenon by liquid, special metal, temperature, humidity etc. Bandwidth of fabricated antenna to VSWR less than 2 is satisfied 11.9% at $890MHz{\sim}1000MHz$. And proposed antenna is circular polarization antenna of operating characteristics that axial ratio is less than 2 and gain is 6dBi.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.1034-1039
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• 2002

In this paper, the design of a dual-polarization rectangular microstrip patch antenna with high isolation between two feeding ports excited by using both an aperture-coupled feed (port 1) and a 3-dimensional microstrip feed (port 2) is presented. From the simulation using the commercial program IE3D, the optimum values of the antenna parameters are investigated at both two feed structures and the optimum antenna is designed and fabricated. Experimental results confirmed that an bandwidth of the antenna is about 17 % and the isolation of two ports is great than 30 dB over all frequency bands.

• Journal of the Korea Convergence Society
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• v.8 no.9
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• pp.9-16
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• 2017

In this paper, sub-microwave oscillator sensor is proposed to non-invasively monitor the glucose concentration level of the human biological tissue by oscillation frequency variation. Inductive slot in the ground plane of the microstrip line is combined with the biological tissue, to realize the resonator as a part of the oscillator sensor. The phantom box mimicking the human tissue is introduced for simulation of the resonator which resonance frequency correspondingly shifts up on three step glucose concentration levels(0, 400, 800 mg/dL). Oscillator sensor circuit is fabricated as a prototype. Pig tissues instead of human is used. Oscillation frequency shift of about 14 MHz per glucose level of 400 mg/dL has been successfully measured around 1,100 MHz. This proves that the proposed sensor is applicable to a blood glucose sensor.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.10
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• pp.28-33
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• 2009

In this paper, we propose the receiver algorithms suitable for the VHF (Very High Frequency) digital link mode-2(VDL Mode-2) system. Unlike conventional digital communication systems using the root raised cosine filter as a transmit and receive filter, raised cosine filter is used as a transmit filter in the VDL Mode-2 system. Hence, it is crucial to design and implement the optimum lowpass receive filter by considering inter-symbol interference and noise performance. On the other hand, due to the short preamble pattern, it is crucial to develop an efficient packet detection algorithm for reliable communication link for the VDL Mode-2 system. Also, frequency offset due to the carrier frequency difference between transmitter and receiver and doppler frequency shift must be estimated and compensated for reliable communication. In this paper, the optimum receive filter, packet detection and frequency offset compensation algorithms are proposed and the performance of the VDL system employing the proposed algorithms are evaluated.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.56-62
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• 2013

We present a rectifier for wireless power transmission using multiplier configuration in layout for MOSFETs which works at 13.56 MHz, designed to fit in CMOS process where conventionally used diodes are replaced with the cross-coupled MOSFETs. Full bridge rectifier structure without comparators is employed to reduce current consumption and to be working up to higher frequency. Multiplier configuration designed in layout reduces time delay originated from parasitic series resistance and shunt capacitance at each finger due to long connecting layout, leading to fast transition from on-state to off-state cross-coupled circuit structure and vice versa. The power conversion efficiency is significantly increased due to this fast transition time. The rectifier is fabricated in $0.11{\mu}m$ CMOS process, RF to DC power conversion efficiency is measured as 86.4% at the peak, and this good efficiency is maintained up to 600 MHz, which is, to our best knowledge, the highest frequency based on cross-coupled configuration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.4
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• pp.279-285
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• 2017

In this paper, the resonator with a parallel plate capacitor is newly proposed around sub-microwave frequency band and applied to earlobe for non-invasive glucose monitoring the human biological tissue. The capacitor including the earlobe as dielectric material is connected to inductive slot in the ground plane of the microstrip line. Based on the simulation, one port resonator circuit is designed and fabricated as a prototype. Three step glucose concentration levels(0, 250, 500 mg/dL) was tested, and its reflection coefficients($S_{11}$) were measured. Owing to high Q resonator more than 100, resonant frequency shift of about 9 MHz per glucose level of 250 mg/dL has been successfully measured. This proves that the proposed sensor is applicable to a blood glucose sensor.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7A
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• pp.569-580
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• 2012

In this paper, an enhanced initial ranging algorithm for large-cell coverage fixed wireless communication system is proposed. In typical wireless communication system such as WiBro, because a round-trip delay between a transmitter and a receiver is within one OFDM (Orthogonal Frequency Division Multiplexing) symbol duration, a frequency-domain differential correlation method is generally used. However, the conventional method cannot be applied due to an increase of a maximum time delay in large-cell system. In case of an accumulative differential method, estimation errors can occur because of frequent sign transitions. In this paper, therefore, we propose an algorithm which can estimate a total timing offset in a ranging channel structure for 15 km cell. The proposed method can improve performance by sign comparison based sign error correction rule between the estimated values and using a weighting scheme based on channel correlation, the number of accumulations, and the noise reduction effect in normalization process. Also, it can estimate the integer timing offset of symbol duration by comparing peak-powers after compensating for the fractional timing offset of symbol duration.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.67-74
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• 2013

IGCC(Integrated Gasification Combined Cycle) system is candidates which can solve the environmental problems including global warming, since it can be easily combined with CCS(Carbon Capture System). In this research, combustion instability characteristics were studied at various fuel which are composed of $H_2/CH_4/CO$ mixture. Mode analysis for instabilities observed experimentally was conducted and the linearly increasing tendency of frequency was observed as the hydrogen content in fuel increases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6296-6302
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• 2014

A new technique, which can increase the channel bandwidth in an optical wireless orthogonal frequency division multiplexing (OFDM) link based on a light emitting diode (LED), is proposed. The technique uses adaptive sampling to convert an OFDM signal to a sparse waveform. In compressive sensing (CS), a sparse signal that is sampled below the Nyquist/Shannon limit can be reconstructed successively with sufficient measurements. The data rate of the proposed CS-based visible light communication (VLC)-OFDM link increases from 30.72 Mb/s to 51.2 Mb/s showing an error vector magnitude (EVM) of 31 % at the quadrature phase shift keying (QPSK) symbol.