• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.277-280
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• 2005

In this paper, we propose a frequency synthesizer for dualband repeater. The dual-band RF technology for applications to the wireless repeater for CDMA and WCDMA mobile communications has been developed in this paper. The dualband PLL module consisted of dual-band VCO and one PLL IC has been developed. The main technological efforts for the dual-band PLL module is to suppress the intermodulation distortion by applying the miniature ceramic filter using the slow wave characteristics. The dual-band miniature RF module including dual-band PLL module and one MCU controller is very attractive for applications to the miniature dual-band RF mobile repeaters.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.214-218
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• 2002

So far, many kinds of researches on the ceramic chip components and MCM-C RF module especially on the 3-dimensional ceramic module using embedded passives have been performed. LTCC system has many kinds of advantages, like low lass, low cost of process, stability of process etc.. But it's so hard to adjust the characteristics of passives in ceramic module after fabrication. So the exact prediction of behavior of components in high frequency region upper than 2 GHz must be made. In this procedure, the exact measurement is need. In this study, many kinds of measurement Jigs are compared and optimized, and measurement methods of each parameter are designed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.241.1-241.1
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• 2014

The large-area high-power radio-frequency (RF) driven ion sources based on the negative hydrogen (deuterium) ion beam extraction are the major components of neutral beam injection (NBI) systems in future large-scale fusion devices such as an ITER and DEMO. Positive hydrogen (deuterium) RF ion sources were the major components of the second NBI system on ASDEX-U tokamak. A test large-area high-power RF ion source (LAHP-RaFIS) has been developed for steady-state operation at the Korea Atomic Energy Research Institute (KAERI) to extract the positive ions, which can be used for the NBI heating and current drive systems in the present fusion devices, and to extract the negative ions for negative ion-based plasma heating and for future fusion devices such as a Fusion Neutron Source and Korea-DEMO. The test RF ion source consists of a driver region, including a helical antenna and a discharge chamber, and an expansion region. RF power can be transferred at up to 10 kW with a fixed frequency of 2 MHz through an optimized RF matching system. An actively water-cooled Faraday shield is located inside the driver region of the ion source for the stable and steady-state operations of RF discharge. The characteristics and uniformities of the plasma parameter in the RF ion source were measured at the lowest area of the expansion bucket using two RF-compensated electrostatic probes along the direction of the short- and long-dimensions of the expansion region. The plasma parameters in the expansion region were characterized by the variation of loaded RF power (voltage) and filling gas pressure.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.55-60
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• 2001

RF MEMS is an exciting emerging technology that has great potential to develop TOC (Transceiver-on-Chip). Applications of the RF MEMS to wireless communications systems are presented. The ability of the RF MEMS technology to enhance the performance and to reduce the size of passive components, in particular, switches, inductors, and tunable capacitors, is addressed. A number of potential wireless system opportunities for the TOC are awaiting the maturation of the RF MEMS technology.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.239-239
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• 2013

The peak klystron power for the PAL (Pohang Accelerator Laboratory) XFEL (X-ray Free Electron Laser) is up to 80 MW which is higher than that of PLS-II LINAC. To prevent the RF breakdown such a high power operation, some of RF components need to be redesigned to reduce the surface electric field gradient to be less than the breakdown gradient at the vacuum-metal surface. For instances, the redesign of the Stanford Linear Accelerator Energy Doubler (SLED) system, the directional coupler and 3dB power splitter using the finite-difference time-domain (FDTD) simulation will be presented.

• Journal of Ginseng Research
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• v.21 no.1
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• pp.13-18
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• 1997

Identification and changes of physiologically active substances during chilling storage of dehisced ginseng (Panax ginseng C. A. Meyer) seeds were analyzed using various preparatory separation methods and purification columns; Dowex 50W and silica gel columns. Seven components with Rf values of 0.20, 0.40, 0.58, 0.66, and 0.70 In solvent system, $CHCl_3$:MeOH=3:1 (v/v), Rf values of 0. 63 and 0.74 in solvent system, $CHCl_3$:MeOH:$H_2O$:=7:3:1 (v/v) were obtained through Dowex 50W and silica gel column chromatographies. Two components with Rf values of 0.20 and 0.63 in the all chilling treatments were detected in the extract obtained through both chromatographies, and only the former component was gradually increased till 4 weeks of chilling storage and then rapidly decreased from 8 to 16 weeks. UV spectra of Rf values of 0.66 and 0.56 were similar to that of cytokinin, but their physiological activities were not found. Rf values of 0.20 showed activity by radish cotyledon expansion bioassay. The component with Rf value of 0.20 was revealed to have a naphthalene in the proposed chemical structure by various NMR techniques.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.99-104
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• 2013

In this paper, we developed a fully integrated downconverter MMIC (monolithic microwave integrated circuit) including Lange coupler and output active balun for millimeter wave applications. Concretely, ${\lambda}$/4 transmission line was added to Lange coupler for size reduction of RF/LO input, and mixed RF/LO signals were applied to gate of the FET of mixer. Active balun was used at output port for a coupling of out-of-phase IF output signals. According to measured results, the proposed downconverter MMIC showed good RF performances. For example, the downconverter MMIC showed an LO leakage power of -25 dBc at IF output port, and a RF-LO isolation of 18 dB. Therefore, off-chip components such as LO rejection filters were not required for a normal operation of the proposed downconverter MMIC. The proposed downconverter MMIC showed a conversion gain of 10.3 dB at RF frequency of 63 GHz. The size of the downconverter MMIC including all active and passive components was $2.2{\times}1.4mm^2$.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.197-200
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• 2000

In this paper, The RF system of W-CDMA receiver is designed and the performance is analyzed. The linearity characteristic and the noise characteristic are presented in the performance. The linearity characteristic is analyzed by PN and IIP3. The noise characteristic is analyzed by NF. In addition, sweeping of the nonlinear components parameter affecting the linear performance is tested and the most maximal possible parameter to maintain the linear performance is introduced. The transceiver RF system of W-CDMA and cdma2000 is designed and presented adapting the nonlinear parameter introduced.

• Journal of IKEEE
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• v.12 no.2
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• pp.75-80
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• 2008

There are many researches to reduce power consumption of battery-operated Transceiver for 2.4 GHz smartRF applications. However, components such as processor, memory and LCD based power managements reach the limit of reducing power consumption. To overcome the limit, this research proposes novel low-power Transceiver and transceiver Hardware Design. Experimental results in the real smartRF Transceiver show that the proposed methods can reduce power consumption additionally than component based power managements.

• ETRI Journal
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• v.33 no.5
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• pp.679-688
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• 2011

A new discrete-amplitude pulse width modulation (DAPWM) scheme for a high-efficiency linear power amplifier is proposed. A radio frequency (RF) input signal is divided into an envelope and a phase modulated carrier. The low-frequency envelope is modulated so that it can be represented by a pulse whose area is proportional to its amplitude. The modulated pulse has at least two different pulse amplitude levels in order that the duty ratios of the pulse are kept large for small input. Then, an RF pulse train is generated by mixing the modulated envelope with the phase modulated carrier. The RF pulse train is amplified by a switching-mode power amplifier, and the original RF input signal is restored by a band pass filter. Because duty ratios of the RF pulse train are kept large in spite of a small input envelope, the DAPWM technique can reduce loss from harmonic components. Furthermore, it reduces filtering efforts required to suppress harmonic components. Simulations show that the overall efficiency of the pulsed power amplifier with DAPWM is about 60.3% for a mobile WiMax signal. This is approximately a 73% increase compared to a pulsed power amplifier with PWM.