• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.62-66
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• 1998

We have studied on the magnetic properties of the specimen with additives Bi$_2$O$_3$and$V_2O_5$ that sintered at 900 $^{\circ}C$ for 4 hours for sybthesizing optimal Ni-Zn-Cu ferrite. Curie temperature rises from 240 $^{\circ}C$ to 270 $^{\circ}C$ as Ni contents increase. Magentic maximum induction$(B_m)$ increases from 2650 G to 3300 G, 3500 G in the specimens with $V_2O_5$ and Bi$_2$O$_3$resectively. On the contrary coercive force $(H_c)$ lowers to 2.05 Oe~1.05 Oe. Permeability all increase in the specimen with additives. In the specimen with additive Bi$_2$O$_3$, we have obtained the low relative loss factor of $6.3{\times}10^{-5}~7.84{\times}10^{-5}$ in the range of 1MHz due to increase of resistivity in grain boundary. In the specimen with additive $V_2O_5$ in spite of increase permeability relative loss factor increase of due to decrease of Q-value.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.171-191
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• 2005

This Technical Memo(TM) was written for the purpose of determining the type of UHF-band power divider which is applicable to KSLV-1. For this, some different kinds of power divider are compared with there types and characteristics. And then, we select three types of power divider(which is Wilkinson power divider, Quadrature hybrid divider and Ring hybrid divider) and perform Schematic and Momentum simulation for finding the optimized characteristics. With this results, in order to demonstrate the selected power divider, we manufactured UHF-band power dividers using FR-4 epoxy plate. By the measured results, we obtain the similar results compare with simulation and fabrication. And Quadrature hybrid power divider is suitable to application to KSLV-1.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.961-966
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• 2009

In this paper, a novel voltage-controlled oscillator(VCO) using the metamaterial broadside coupled spiral resonators(BC-DSRs) is presented for reducing the phase noise. For reducing of the phase noise, the series spiral structures have been applied for the signal plane and ground plane at each in order to have the large coupling. Compared with the conventional VCO, the proposed VCO has the larger coupling coefficient constant, which makes a higher Q-factor and has reduced the phase noise of the VCO. The proposed VCO has the phase noise of $-121{\sim}-117.16\;dBc$/Hz at 100 kHz in the tuning range, $5.749{\sim}5.853\;GHz$. The figure of merit(FOM) of this VCO is $-198.45{\sim}-194.77\;dBc$/Hz at 100 Hz in the same tuning range, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.3
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• pp.284-290
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• 2004

In this paper, two types of thin nim bulk acoustic resonator(TFBAR) ladder filters are desisted and fabricated to analyze the effects of on-wafer inductor integration. To suppress the overmode phenomenon a 1 $\mu\textrm{m}$ thick air-gap is fabricated under the TFBAR and aluminum nitride is used for piezoelectric material, while platinum is employed for the top and bottom electrodes. The Tx filter in a duplexer, which usually has a steeper skirt characteristics o the right side of the passband, is designed with four serial and two shunt resonators, namely, a 4/2 stage. Similarly, the Rx filter is devised with a 3/4 stage to create a mirrored image of the Tx filter passband characteristics. Fabricated on-wafer spiral inductors with underpass reveals the Q factor of 5～9 at 2 ㎓. Inductor integrated filters have approximately 10 to 12 ㏈ out-of-band rejection improvement, when compared to the original filters.

• Journal of the Korean Magnetics Society
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• v.6 no.6
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• pp.367-374
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• 1996

The developmement of electronic machine industries requires miniature of size as well as increasement of driving frequency in electronic parts, recently. To realize micro-struture of magnetic devices, in this study, we fabricated thin film inductors by using thin film manufacturing techniques such as photolithography and wet etching process, and these devices are measured at high frequency range of 1 MHz~1 GHz. The results are as follows. The accurate measuring technique by using network analyzer system having microstrip line was established. The manufactured inductors are fabricated with several ten micrometers by means of wet etching process known as easier and more economic than dry etching process. VVhen the device size of two types (spiral, meander) is the same, inductance value L and quality factor Q of spiral type devices are larger than those of meander type, but driving frequency of spiral type is lower than that of meander type due to increasement of inductance L. It is necessary to decrease resistance value R by increasing cross section of the conductor film coil. Thus high frequency measuring method would be a very useful for another measuring fields of the range over several hundreds MHz.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.60-67
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• 2008

An all-optical 4-bit Gray code to binary coded decimal (BCD) converter by means of commercially available numerical analysis tool (VPI) was demonstrated, for the first time to our knowledge. Circuit design approach was modified appropriately in order to fit the electrical method on an all-optical logic circuit based on a cross gain modulation (XGM) process so that signal degradation due to the non-ideal optical logic gates can be minimized. Without regenerations, Q-factor of around 4 was obtained for the most severely degraded output bit (least significant bit-LSB) with 2.5 Gbps clean input signals having 20 dB extinction ratio. While modifying the two-level simplification method and Karnaugh map method to design a Gray code to BCD converter, a general design concept was also founded (one-level simplification) in this research, not only for the Gray code to BCD converter but also for any general applications.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.7-11
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• 2006

In this paper, it is reported that film-bulk-acoustic resonator with high c-axis oriented AIN film on $Mo/SiO_2/Si(100)$ using metal-organic-chemical-vapor deposition was fabricated. The resonant frequency and anti-resonant frequency of the fabricated resonator were observed with 3.189[GHz] and 3.224[GHz], respectively. The quality factor and the effective electromechanical coupling coefficient(${k_{eff}}^2$) were measured with 24.7 and 2.65[%], respectively. The conditions of AIN deposition were substrate temperature of $950[^{\circ}C]$, pressure of 20Torr, and V-III ratio of 25000. A high c-axis oriented AIN film with $4{\times}10^{-5}[\Omega{cm}]$ resistivity of Mo bottom electrode and $4[^{\circ}]$ of AIN(0002) full-width at half-maximum(FWHM) on $Mo/SiO_2/Si(100)$ was grown successfully. The FWHM value of deposited AIN film is useful for the RF band pass filter specification for GHz-band wireless local area network.

• The Korean Journal of Financial Management
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• v.21 no.2
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• pp.99-123
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• 2004

We focus in this study on incremental financing decisions and estimate a logit model for the probability a firm will choose a private placement over a public bond issue. We hypothesize that information asymmetry, financial risk, agent cost, and proprietary information may affect a firm's choice between public debt and private placements. We find that as the size of firm increases, the probability of choosing a private placement declines significantly. The age of the firm, however, is not a significant factor affecting the firm's choice between public and privately-placed bond. The coefficients on the firm's leverage and non-investment grade dummy are significantly positive, meaning firms with high financial risk and credit risk select private placements. The findings regarding agency-related variables, PER and Tobin's Q, are somewhat complex. We find significant evidence that firms with high PER prefer private placements to public bonds, suggesting that borrowers with options to engage in asset substitution or underinvestment are more likely to choose private placements. The coefficient of Tobin's Q is negative, but not significant, which weakly support the hold-up hypothesis. When we construct an interaction term on the Tobin's Q with a non-investment rating dummy, however, the Tobin's Q interaction term becomes positive and significant. Thus, high Tobin's Q firms with a speculative rating are significantly more likely to choose a private placement, regardless of the potential hold-up problems. The ratio of R&D to sales, proxy for proprietary information, is positively significant. This result can be interpreted as evidence in favor of a role for proprietary information in the debt sourcing decision process for these firms.

• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.469-475
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• 2005

An integrated photonic microwave bandpass filter has been proposed and demonstrated incorporating a coherently coupled microring resonator in low-loss polymers. The proposed device may feature compact site, simple structure, tuning via the thermooptic and electrooptic effect, and flexible integration with other electrical and optical devices. The resonator was designed to have an extremely small bandwidth so that it could be used to selectively pass the optical signal carrying the microwave signal to attain efficient bandpass filtering. We made and tested two resonators with a single ring and double rings, and performed a theoretical fitting of their measured transfer curves to predict the performance of the microwave filters based on them precisely. It was found that as the number of the rings used for the resonator increases, the bandwidth gets smaller, the rolloff sharper, and the band rejection higher. Finally our filter exhibited the center frequency of 10GHz, the 3-dB bandwidth of 1.0GHz, the corresponding quality (Q) factor of 10, and the rejection outside of the passband of more than 25dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1167-1172
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• 2013

This paper presents a X-band doppler radar with high conversion gain using a self-oscillating-mixer(SOM) that oscillation and frequency mixing is realized at the same time. To improve phase noise of the SOM oscillator, a ${\lambda}/2$ slotted square patch resonator(SSPR) was proposed, which shows high Q-factor of 175.4 and the 50 % reduced circuit area compared to the conventional resonator. To implement the low power system, low biasing voltage of 1.7 V was supplied. To enhance the conversion gain of the SOM, bias circuit is configured near the pinch-off region of transistor, and the conversion gain was optimized. The output power of the proposed SOM was -3.16 dBm at 10.65 GHz. A high conversion gain of 9.48 dB was obtained whereas DC Power consumption is relatively low about 7.65 mW. The phase noise is -90.91 dBc/Hz at 100 kHz offset. The figure-of-merit(FOM) of the proposed SOM was measured as -181.8 dBc/Hz, which is supplier to other SOMs by more than about 7 dB.