• Journal of the Korean Institute of Telematics and Electronics C
• /
• v.36C no.2
• /
• pp.54-61
• /
• 1999

This paper describes the design of a 4-Mbps wireless infrared data transceiver chip. The receiver consits of the analog front-end, clock recovery and frame generator, and demodulator. The transmitter consists of the demodulator and LED driver. The versatile analog front- end consisting of multiple amplifiers makes it possible for the chip to be applied to various infrared environments by compensating DC and offset signal components. A 4PPM (pulse position modulation) scheme is used for data transfer in order to meet the IrDA standards. The chip was fabricated in a $0.8-{\mu}m$ 2-poly, 2-metal CMOS technology and dissipates 122mW for ${\pm}2.5V$ supply.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.6
• /
• pp.91-98
• /
• 2004

This paper proposes a PCB plane model for generic SPICE circuit simulators. The proposed model reflects two frequency-dependent losses, namely skin and dielectric losses. After power/ground plane pair is divided into arrays of unit-cells, each unit-cell is modeled using a transmission line and two loss models. The loss model is composed of a resistor for DC loss, series HL ladder circuit for skin loss and series RC ladder circuit for dielectric loss. To verify the validity of the proposed model, it is compared with SPICE ac analysis using frequency-dependent resistors. Also, we show that the estimation results using the proposed model have a good correlation with that of VNA measurement for the typical PCB stack-up structure of general desktop PCs. With the proposed model, not only ac analysis but also transient analysis can be easily done for circuits including various non-linear/linear devices since the model consists of passive elements onl.

• International Journal of Control, Automation, and Systems
• /
• v.6 no.2
• /
• pp.186-193
• /
• 2008

The Internet's low cost and ubiquity present an attractive option for real-time distributed control of processes on the factory floor. When integrated with the Internet, the LonWorks open control network can give ubiquitous accessibility with the distributed control nature of information on the factory floor. One of the most important points in real-time distributed control of processes is timely response. There are many processes on the factory floor that require timely response. However, the uncertain time delay inherent in the network makes it difficult to guarantee timely response in many cases. Especially, the transmission characteristics of the LonWorks/IP network show a highly stochastic nature. Therefore, the time delay problem has to be resolved to achieve high performance and quality of the real-time distributed control of the process in the LonWorks/IP Virtual Device Network (VDN). It should be properly predicted and compensated. In this paper, a new distributed control scheme that can compensate for the effects of the time delay in the network is proposed. It is based on the PID controller augmented with the Smith predictor and disturbance observer. Designing methods for output feedback filter and disturbance observer are also proposed. Tracking position control experiment of a geared DC Servo motor is performed using the proposed control method. The performance of the proposed controller is compared with that of the Internal Model Controller (IMC) with the Smith predictor. The result shows that the performance is improved and guaranteed by augmenting a PID controller with both the Smith predictor and disturbance observer under the stochastic time delay in the LonWorks/IP VDN.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.11 no.4
• /
• pp.229-237
• /
• 2011

In this paper, a 60 GHz LTCC SiP with low-power CMOS OOK modulator and demodulator is presented. The 60 GHz modulator is designed in a 90-nm CMOS process. The modulator uses a current reuse technique and only consumes 14.4-mW of DC power in the on-state. The measured data rate is up to 2 Gb/s. The 60 GHz OOK demodulator is designed in a 130nm CMOS process. The demodulator consists of a gain boosting detector and a baseband amplifier, and it recovers up to 5 Gb/s while consuming low DC power of 14.7 mW. The fabricated 60 GHz modulator and demodulator are fully integrated in an LTCC SiP with 1 by 2 patch antenna. With the LTCC SiP, 648 Mb/s wireless video transmission was successfully demonstrated at wireless distance of 20-cm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.9 no.4
• /
• pp.542-551
• /
• 1998

In this study, a method of error compensation for channel gain imbalance, phase imbalance and local oscillator leakage in the modulator of frequency direct conversion is suggested. The compensation of channel imbalance can be carried out by using the received power after transmitting test signal. By applying this method, the phase imbalance conversion with frequency can be easily compensated since this method is rarely affected by the transmission channel. It is confirmed that the algorithm proposed in this study(iteration coefficient=11) converges faster than conventional algorithm(iteration coefficient=43). From the numerical results, the DC-offset, channel gain, phase imbalance compensation coefficient and iteration number converges into($f_1$=0.0199999, $f_2$=-0.050001, $C_{22}$=0.9133, $C_{12}$=-0.0524, N=13) when the local oscillator leakage is not considered. However, it converges into($f_1$=-0.02, $f_2$=-2.2476, $C_{22}$=0.9133, $C_{12}$=-0.0524, N=16) when the local oscillator leakage is considered.

• Journal of Power Electronics
• /
• v.18 no.1
• /
• pp.225-233
• /
• 2018

This paper proposes a universal system control strategy for voltage source converter (VSC) based high voltage direct current (HVDC) systems. The framework of the designed control strategy consists of five layer structures considering the topology and control characteristics of the VSC-HVDC system. The control commands sent from the topmost layer can be transmitted to the next layer based on the existing communication system. When the commands are sent to each substation, the following transmission of commands between the four lower layers are realized using the internal communication system while ignoring the communication delay. This hierarchical control strategy can be easily applied to any VSC-HVDC system with any topology. Furthermore, an integrated controller for each converter is designed and implemented considering all of the possible operating states. The modular-designed integrated controller makes it quite easy to extend its operating states if necessary, and it is available for any kind of VSC. A detailed model of a VSC-HVDC system containing a DC hub is built in the PSCAD/EMTDC environment. Simulation results based on three operating conditions (the start-up process, the voltage margin control method and the master-slave control method) demonstrate the flexibility and validity of the proposed control strategy.

• Korean Journal of Plant Tissue Culture
• /
• v.24 no.3
• /
• pp.167-173
• /
• 1997

The embryogenic callus (EC), from which somatic embryos could be induced, was compared with nonembryogenic callus(NE) to study the origin and features of totipotent cell in water dropwort (Oenanthe stolonifera DC). To induce and maintain of EC and the NE, meristematic stem and immature floret were inoculated in MS media supplemented with 1 mg/L 2,4-D, and with 2.5 mg/L NAA and 5mg/L BA, respectively, The EC was not induced from the NE even after subculturing in MS medium supplemented with 1 mg/L 2,4-D. Plantlets were not regenerated from the NE in hormone-free medium. In histochemical comparison of the EC with the NE by light microscopy, the EC had smaller cells in size, dense cytoplasm, and more starch granules of cells compared to the NE cells. The cell from the EC, as observed by transmission electron microscopy, had smaller vaculoes, well developed ribosomes, mitochondria, and endoplasmic reticulum, whereas the cells from the NE had larger vacuoles and underdeveloped organelles. In protein pattern from NE, EC and Somatic embryo (SE), as analyzed by SDS polyacrylamide gel electrophoresis, different proteins specific for tissue were observed: 17 and 28 KD for NE, 50, 52, 57, 66, 68 KD for EC and 20 KD for SE. DNA polymorphism was also observed between EC and NE as analyzed by RAPD (randomly amplified polymorphic DNA) method. The origin of totipotent stem cell and the relationship between irreversible genomic change arose in differentiation and the loss of totipotency in plant were discussed.

• Corrosion Science and Technology
• /
• v.18 no.5
• /
• pp.206-211
• /
• 2019

Silicon carbide (SiC) thin films become superhard when they have microstructures of nanocolumnar crystalline grains (NCCG) with an intergranular amorphous SiC matrix. We investigated the role of ion bombardment and deposition temperature in forming the NCCG in SiC thin films. A direct-current (DC) unbalanced magnetron sputtering method was used with pure Ar as sputtering gas to deposit the SiC thin films at fixed target power of 200 W and chamber pressure of 0.4 Pa. The Ar ion bombardment of the deposited films was conducted by applying a negative DC bias voltage 0-100 V to the substrate during deposition. The deposition temperature was varied between room temperature and $450^{\circ}C$. Above a critical bias voltage of -80 V, the NCCG formed, whereas, below it, the SiC films were amorphous. Additionally, a minimum thermal energy (corresponding to a deposition temperature of $450^{\circ}C$ in this study) was required for the NCCG formation. Transmission electron microscopy, Raman spectroscopy, and glancing angle X-ray diffraction analysis (GAXRD) were conducted to probe the samples' structural characteristics. Of those methods, Raman spectroscopy was a particularly efficient non-destructive tool to analyze the formation of the SiC NCCG in the film, whereas GAXRD was insufficiently sensitive.

• Korean Journal of Optics and Photonics
• /
• v.17 no.5
• /
• pp.401-411
• /
• 2006

We propose an optical encryption/decryption technique for a security system based on 2-step phase-shifting digital holography. Phase-shilling digital holography is used for recording phase and amplitude information on a CCD device. 2-step phase-shifting is implemented by moving the PZT mirror with phase step of 0 or ${\pi}/2$. The binary data and the key are expressed with random code and random phase patterns. The digital hologram is a Fourier transform hologram and is recorded on CCD with 256 gray level quantization. We remove the DC term of the digital hologram fur data reconstruction, which is essential to reconstruct the original binary input data/image. The error evaluation fer the decrypted binary data is analyzed. One of errors is a quantization error in detecting the hologram intensity on CCD, and the other is generated from decrypting the data with the incorrect key. The technique using 2-step phase-shifting holography is more efficient than a 4-step method because 2-step phase-shifting holography system uses less data than the 4-step method for data storage or transmission. The simulation shows that the proposed technique gives good results fur the optical encryption of binary information.

• Journal of Advanced Navigation Technology
• /
• v.23 no.2
• /
• pp.166-171
• /
• 2019

This paper has designed a current mode class D power amplifier to increase the transmission efficiency of a 6.78 MHz wireless power transfer (WPT) transmitter and to ensure stable characteristics even when the transmitting and receiving coil intervals change. By reducing the loss due to the parasitic capacitor component of the transistor, which limits the theoretical efficiency of the linear amplifier, this research has improved the efficiency of the power amplifier. The circuit design simulator was used to design the high efficiency amplifier, and the power output and efficiency characteristics according to the load impedance change have been simulated and verified. In the simulation, 42.1 dBm output and 95% efficiency was designed at DC bias 30 V. The power amplifier was fabricated and showed 91% efficiency at the output of 42.1 dBm (16 W). The transmitting and receiving coils were fabricated for wireless power transfer of the drone, and the maximum power added efficiency was 88% and the output power was $42.1dBm{\pm}1.7dB$ according to the load change causing from the coil intervals.