• Korean Journal of Materials Research
• /
• v.5 no.8
• /
• pp.997-1004
• /
• 1995

Intermetallic compound NbAl₃and amorphous phases were synthesized by mechanical alloying of elemental powder mixtures of niobium and aluminum. The composition of the powder mixtures was Nb-45wt%Al(75at%Al). The mechanical alloying was performed with a high energy SPEX 8000 mixer/mill up to 72 hrs. The resulting powders were analyzed by XRD, DTA, SEM and TEM. The mechanically alloyed powders exhibited lamellar structures in the early stage. And the elements of Nb and Al were homogeneously distributed over the Powder when a steady state was reached. An intermetallic compound, NbAl₃, was formed by mechanical alloying for 4 hrs. The mechanically alloyed powders exhibited a large exotherm around 600℃, corresponding to formation of stable NbAl₃and stress relief.

• ETRI Journal
• /
• v.30 no.4
• /
• pp.526-534
• /
• 2008

This paper presents a fully integrated 0.13 ${\mu}m$ CMOS MB-OFDM UWB transmitter chain (mode 1). The proposed transmitter consists of a low-pass filter, a variable gain amplifier, a voltage-to-current converter, an I/Q up-mixer, a differential-to-single-ended converter, a driver amplifier, and a transmit/receive (T/R) switch. The proposed T/R switch shows an insertion loss of less than 1.5 dB and a Tx/Rx port isolation of more than 27 dB over a 3 GHz to 5 GHz frequency range. All RF/analog circuits have been designed to achieve high linearity and wide bandwidth. The proposed transmitter is implemented using IBM 0.13 ${\mu}m$ CMOS technology. The fabricated transmitter shows a -3 dB bandwidth of 550 MHz at each sub-band center frequency with gain flatness less than 1.5 dB. It also shows a power gain of 0.5 dB, a maximum output power level of 0 dBm, and output IP3 of +9.3 dBm. It consumes a total of 54 mA from a 1.5 V supply.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.4
• /
• pp.1988-1992
• /
• 2011

Polypropylene (PP)-SEBS/silicate composites with PP content of 35, 40, and 45wt% were fabricated by melt compounding at $200^{\circ}C$, using lab scale Brabender mixer. The content of silicate was fixed at 5wt%. The thermal properties of the PP-SEBS/silicate composites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). The melting temperature of PP-SEBS compound decreased up to $141^{\circ}C$ with SEBS content. TGA result indicates an increase in degradation temperature when the silicate was added in the PP-SEBS compound. The rheological properties of the compounds were measured by dynamic Rheometer. PP-SEBS/silicate composite indicates higher shear thinning and elastic property than PP-SEBS compound. Van Gurp-Palmen analysis was applied in order to certify an increase in elasticity.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.5 s.248
• /
• pp.430-437
• /
• 2006

The mixing effect is studied by comparing rotating and oscillating stirrers in the micro channel. The cases of Re=10 to 80 with various stirring speeds are considered to analysis the effect of Re and stirrer speed for the mixing. Under Re=20, the oscillating stirrer represents better mixing rate than the rotating stirrer up to the critical stirrer speed which has a maximum efficiency. Over Re=30, the results of oscillating and rotating stirrer show that the faster the stirrer speed, the higher the mixing effect within the concerned stirrer speed range and the oscillating stirrer keeps the higher mixing rate. It was found that the mixing effect is a function which has an optimum of the Reynolds number and the stirrer speed. The D2Q9 Lattice Boltzmann Method is used due to the merits of calculation for the unsteady flow with moving boundary.

• Proceedings of the IEEK Conference
• /
• 2005.11a
• /
• pp.575-578
• /
• 2005

We report on a low-cost V-band wireless transceiver with no use of any local oscillator in the receiver block using a self-heterodyne architecture. V-band Microwave monolithic IC (MMIC) modules were developed to demonstrate the wireless transceiver using coplanar waveguide (CPW) and GaAs PHEMT technologies. The MMIC modules such as the MMIC low noise amplifier (LNA), medium power amplifier (MPA) and the up/down-mixer were installed in the transceiver system. To interface the MMIC chips with the component modules for the transceiver system, CPW-to-waveguide fin-line transition modules of WR-15 type were designed and fabricated. The fabricated LNA modules showed a $S_{21}$ gain of 8.4 dB and a noise figure of 5.6 dB at 58 GHz. The MPA modules exhibited a gain of 6.9 dB and a $P_1$ $_{dB}$ of 5.4 dBm at 58 GHz. The conversion losses of the up-mixer and the down-mixer module were 14.3 dB at a LO power of 15 dBm, and 19.7 dB at a LO power of 0 dBm, respectively. From the measurement of V-band wireless transceiver, a conversion gain of 0.2 dB and a P $_{1dB}$ of 5.2 dBm were obtained in the transmitter block. The receiver block showed a conversion gain of 2.1 dB and a P $_{1dB}$ of -18.6 dBm. The wireless transceiver system demonstrated a successful data transfer within a distance of 5 meters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.7
• /
• pp.661-668
• /
• 2004

A novel method to reject the spurious signals which are occurred at Weaver-type low-IF transmitter was proposed in this paper. The spurious signals are generated by the gain and phase imbalances of I/Q channel or imperfect characteristics of 90$^{\circ}$ phase shifter in local oscillator for I/Q channel source. By deriving the gain and phase-based functions from RF spurious signal with the channel imbalance information, the lie channel imbalances were deduced as functions with magnitude and sign dependent on I/Q channel imbalance degree. The proposed method compensates the estimated I/Q channel imbalances by correlation values between the down-converted signal obtained by squaring the output signal itself using a simple mixer and the modified baseband signal. By comparing two signals after A/D conversion, the magnitude and sign of each type of imbalances can be determined separately and simultaneously. Based on the I/Q channel imbalance compensation, the spurious signals can be reduced by adjusting the gain and phase values of I or Q channel signal. The way to estimate the channel imbalances of the up-conversion mixer was presented and verified by using theoretical derivations and computer simulations.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.5 no.3
• /
• pp.210-219
• /
• 2005

We report on a low-cost V-band wireless transceiver with no use of any local oscillator in the receiver block using a self-heterodyne architecture. V-band millimeter-wave monolithic IC (MMIC) modules were developed to demonstrate the wireless transceiver using coplanar waveguide (CPW) and GaAs PHEMT technologies. The MMIC modules such as the MMIC low noise amplifier (LNA), medium power amplifier (MPA) and the up/down-mixer were installed in the transceiver system. To interface the MMIC chips with the component modules for the transceiver system, CPW-to-waveguide fin-line transition modules of WR-15 type were designed and fabricated. The fabricated LNA modules showed a $S_{21}$ gain of 8.4 dB and a noise figure of 5.6 dB at 58 GHz. The MPA modules exhibited a gain of 6.9 dB and a $P_{1dB}$ of 5.4 dBm at 58 GHz. The conversion losses of the up-mixer and the down-mixer module were 14.3 dB at a LO power of 15 dBm, and 19.7 dB at a LO power of 0 dBm, respectively. From the measurement of V-band wireless transceiver, a conversion gain of 0.2 dB and a $P_{1dB}$ of 5.2 dBm were obtained in the transmitter block. The receiver block showed a conversion gain of 2.1 dB and a $P_{1dB}$ of -18.6 dBm. The wireless transceiver system demonstrated a successful data transfer within a distance of 5 meters.

• Journal of Industrial Technology
• /
• v.25 no.B
• /
• pp.127-133
• /
• 2005

Manufacturing methods of Nano particles can be distinguished by top-down technology as physical method and bottom-up technology as chemical synthetic method. Top-down technology is a kind of method for making microstructure as like carving after forming a macroscopic structure in advance and its typical methods are ball milling, gas condensation method and so on. Nano Particles synthesized by bottom-up method have got to do dispersing process for using them as actual nano particles because their viscosity are very strong and so easy to shape cohesive substances. Therefore, this study is about a particle separating device which separates a certain constant size of grains processed already in mill and mixer because we mostly use media agitating mill as a device of milling and dispersing and we necessarily use very slight balls as media for manufacturing nano particles in the machine. The centrifugal device has been designed for passing and separating below a certain type of grain size after final process of particles in the mill.

• ETRI Journal
• /
• v.34 no.5
• /
• pp.649-654
• /
• 2012

This paper presents a novel 16-quadrature-amplitude-modulation (QAM) E-band communication system. The system can deliver 10 Gbps through eight channels with a bandwidth of 5 GHz (71-76 GHz/81-86 GHz). Each channel occupies 390 MHz and delivers 1.25 Gbps using a 16-QAM. Thus, this system can achieve a bandwidth efficiency of 3.2 bit/s/Hz. To implement the system, a driver amplifier and an RF up-/down-conversion mixer are implemented using a $0.1{\mu}m$ gallium arsenide pseudomorphic high-electron-mobility transistor (GaAs pHEMT) process. A single-IF architecture is chosen for the RF receiver. In the digital modem, 24 square root raised cosine filters and four (255, 239) Reed-Solomon forward error correction codecs are used in parallel. The modem can compensate for a carrier-frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of $10^{-5}$ at a signal-to-noise ratio of about 21.5 dB.

• ETRI Journal
• /
• v.36 no.2
• /
• pp.206-213
• /
• 2014

This paper presents a novel 90 GHz band 16-quadrature amplitude modulation (16-QAM) orthogonal frequency-division multiplexing (OFDM) communication system. The system can deliver 6 Gbps through six channels with a bandwidth of 3 GHz. Each channel occupies 500 MHz and delivers 1 Gbps using 16-QAM OFDM. To implement the system, a low-noise amplifier and an RF up/down conversion fourth-harmonically pumped mixer are implemented using a $0.1-{\mu}m$ gallium arsenide pseudomorphic high-electron-mobility transistor process. A polarization-division duplex architecture is used for full-duplex communication. In a digital modem, OFDM with 256-point fast Fourier transform and (255, 239) Reed-Solomon forward error correction codecs are used. The modem can compensate for a carrier-frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of $10^{-5}$ at a signal-to-noise ratio of about 19.8 dB.