• Bulletin of the Korean Chemical Society
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• v.16 no.10
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• pp.929-933
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• 1995

The electronic band structure and electrical properties of KMo4O6 containing chains of condensed molybdenum octahedra are analyzed by means of the extended Hu&ckel tight-binding method. KMo4O6 has partially filled bands of 1D as well as 3D character. They also exhibit the anisotropic band dispersions with bandwidths much larger along the c* axis than along the directions perpendicular to it. Thus, conduction electrons are essentially delocalized along the c* direction (i.e., the chain of condensed molybdenum octahedra) in the solid. The 1D band of two partially filled d-block bands leads to Fermi surface nesting with the wave vector q=0.3c*. The CDW instability due to this nesting is expected to cause the phase transition associated with the resistivity anomaly at low temperature. The characteristics of metallic behavior in the crystallographic ab plane are explained on the basis of the unnested 2D Fermi surfaces.

• Elastomers and Composites
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• v.53 no.4
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• pp.226-233
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• 2018

Elastomers based on the thermoplastics are widely used in rubber industries. Thermoplastic elastomers have the advantages of an easy shaping process and elimination of recycling problems. Thermoplastic polyester elastomer (TPE) is used for making rubber bands in wearable devices and its applications are increasing. In this study, five wrist bands were designed and their mechanical behaviors were examined by computer simulation, using hyper elastic models, Mooney-Rivlin and Ogden models, and a linear elastic model. Simulation results were compared and discussed in terms of band design and material model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1236-1242
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• 2014

In this work, a D-band VCO(Voltage Controlled Oscillator) has been developed in a 65-nm CMOS technology. The circuit was designed based on push-push mechanism. The output oscillation frequency of the fabricated VCO varied from 152.7 GHz to 165.8 GHz, and the measured output power was from -17.3 dBm to -8.7 dBm. A phase noise of -90.9 dBc/Hz is achieved at 10 MHz offset. The chip size of the circuit is $470{\mu}m{\times}360{\mu}m$ including the probing pads.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.4
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• pp.192-197
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• 2009

This paper presents the design and measurement of a 2.4/5.2-GHz dual band VCO with a balanced frequency doubler in $0.18\;{\mu}m$ CMOS process. The topology of a 2.4 GHz VCO is a cross-coupled VCO with a LC tank and the frequency of the VCO is doubled by a frequency balanced doubler for a 5.2 GHz VCO. The gate bias matching network for class B operation in the balanced doubler is adopted to obtain as much power at 2nd harmonic output as possible. The average output powers of the 2.4 GHz and 5.2 GHz VCOs are -12 dBm and -13 dBm, respectively, the doubled VCO has fundamental harmonic suppression of -25 dB. The measured phase noises at 5 MHz frequency offset are -123 dBc /Hz from 2.6 GHz and -118 dBc /Hz from 5.1 GHz. The total size of the dual band VCO is $1.0\;mm{\times}0.9\;mm$ including pads.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.967-973
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• 2009

In this paper, X-band satellite communication oscillator of double phase locked is implemented by constructing a couple of phased-locked loop, and then we have analyzed the phase noise of designed PLL-DRO. The designed phase-locked oscillator is consist of series feedback DRO, frequency divider, phase detector, loop filter and programmable PLL-IC. By dividing oscillation frequency of 12.6 GHz into two frequencies, it exhibits output power of 15.32 dBm at 6.3 GHz. Phase noises of implemented oscillator are -81 dBc/Hz@100Hz, -100.86 dBc/Hz@1 kHz, -111.12 dBc/Hz@10 kHz, -116 dBc/Hz@100 kHz and -140.49 dBc/Hz@1 MHz respectively. These indicate excellent stable operation of oscillator and very good phase noise characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7A
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• pp.545-551
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• 2012

In this paper, K-band multi-channel receiver was designed and fabricated for low noise amplification and down conversion to L-band. The fabricated multi-channel receiver incorporates GaAs-HEMT LNA(Low noise amplifier) which provides less than a 2 dB noise figure, IR(Image Rejection) Filter for rejection of image frequency, IR(Image rejection) mixer to reject a image frequency and improve an IMD(Intermodulation Distortion) characteristic. Test results of the fabricated multi-channel receiver show less than a 3.8 dB noise figure, conversion gain of more than 27dB, and IP1dB(Input 1dB Gain Compression Point) of -9.5 dB and over.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.909-915
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• 2010

In this paper, the unequal power divider based on CRLH (Composite Right/Left-Handed) transmission line with dual-band characteristic is proposed. They consist of dual-band branch line hybrid coupler, the connection between input and isolation port of hybrid coupler and ${\lambda}/4$ impedance transformer. When the transmission line between input and isolation port of hybrid coupler is asymmetrical connected, the divider is obtained the output results of the equal phase and unequal power dividing ratio. The simulation results of the divider represent the power ratio of 0 dB ~ 20 dB. To validate a function of divider, the hybrid coupler and transformer with 880 MHz and 1850 MHz is implemented. As a result, the proposed unequal divider obtains the power ratio of 3.2 dB ~ 8.8 dB at 880 MHz and 2.5 dB ~ 14.0 dB at 1850 MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.704-709
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• 2007

In this paper, a CPW band-pass filter with a rejection band is proposed for UWB(Ultra-Wideband) communication systems. The proposed filter has a band-pass characteristic of wide-band by inserting only a slot in $50{\Omega}$ transmission line. To obtain the band-rejection function at WLAN frequency band($5.15{\sim}5.725GHz$), the designed filter is combined with folded slot resonators on the ground plane of the CPW structure. The fabricated CPW band-pass filter shows a compact size of $15.35{\times}13.60mm$, a wide passband of 2.8 GHz to 9.8 GHz and the narrow stop-band of 5.15 GHz to 5.71 GHz for 3-dB bandwidth. Also, the measured group delay is less than 400 psec throughout the operation frequency band except the rejection band.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.7 s.337
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• pp.41-48
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• 2005

We design and fabricate 3-dB tandem directional coupler using the coplanar waveguide structure which is applicable to balanced amplifiers and mixers for 60 GHz wireless local area network system. The coupler comprises the multiple-sectional parallel-coupled lines to facilitate the fabrication process, and enable smaller device size and higher directivity than those of the conventional 3-dB coupler employing the edge-coupled line. In this study, we adopt the structure of two-sectional parallel-coupled lines of which each single-coupled line has a coupling coefficient of -8.34 dB and airbridge structure to monolithically materialize the uniplanar coupler structure instead of using the conventional multilayer or bonded structure. The airbridge structure also supports to minimize the parasitic components and maintain desirable device performance in V-band (50$\~$75 GHz). The measured results from the fabricated couplers show couplings of 3.S$\~$4 dB and phase differences of 87.5$^{\circ}{\pm}1^{\circ}$ in V-band range and show directivities higher than 30 dB at a frequency of 60 GHz.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1994.04a
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• pp.43-48
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• 1994

A wide band design method of an electromagnetic wave absorber using exponentially tapered ferrite which has very wide band frequency characteristics is proposed and discussed. The wide band electromagnetic wave absorber can be designed by the proposed equivalent material constants method for the regions varying spatially in the shape of ferrite. Furthemore the wide band ferrite electromagnetic wave absorbers with taper which have not only excellent reflectivity frequency characteristics but also the band width of 30MHz to 2150 or 2450MHz under the tolerance limits of -20dB reflectivity were designed.