• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.8
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• pp.401-406
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• 2004

In this experimentation, we investigated the characteristics of electromagnetic wave absorption of ferroxplana powder and silicone rubber composite. Ferroxplana was prepared by flux method at low temperature. The crystallization, magnetic properties and particle morphology of the obtained ferroxplana powder were investigated by using XRD, VSM and SEM. The particle size of ferroxplana powder was 2∼4$\mu\textrm{m}$ at the ratio of R=26, The coercivity and saturation magnetization of ferroxplana powder increased slightly with increase of temperature, The magnetic loss was the main factor of electromagnetic wave absorption of ferroxplana powder and silicone rubber composite, The maximum reflection loss of composite was about -l5dB below 4GHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.252-255
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• 1999

The effect of calcination temperature(1st and 2nd calcining at 110$0^{\circ}C$ , 120$0^{\circ}C$ and 130$0^{\circ}C$ respectively) on physical properties of BMNT Ceramics ware investigated. The optimum 1st and 2nd calcination temperature were 120$0^{\circ}C$ , and sintering temperature was 155$0^{\circ}C$. In this condition, the sintering density was 7.53 [g/㎤] and the dielectric constant, Q.f$_{0}$ and $\tau$$_{r}$ were 26, 80, 300[GHz] and +1.5[ppm/$^{\circ}C$] respectively in the microwave range.e.e.

• ETRI Journal
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• v.26 no.3
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• pp.229-240
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• 2004

This paper reports on our development of a dual-mode transceiver for a CMOS high-rate Bluetooth system-onchip solution. The transceiver includes most of the radio building blocks such as an active complex filter, a Gaussian frequency shift keying (GFSK) demodulator, a variable gain amplifier (VGA), a dc offset cancellation circuit, a quadrature local oscillator (LO) generator, and an RF front-end. It is designed for both the normal-rate Bluetooth with an instantaneous bit rate of 1 Mb/s and the high-rate Bluetooth of up to 12 Mb/s. The receiver employs a dualconversion combined with a baseband dual-path architecture for resolving many problems such as flicker noise, dc offset, and power consumption of the dual-mode system. The transceiver requires none of the external image-rejection and intermediate frequency (IF) channel filters by using an LO of 1.6 GHz and the fifth order onchip filters. The chip is fabricated on a $6.5-mm^{2}$ die using a standard $0.25-{\mu}m$ CMOS technology. Experimental results show an in-band image-rejection ratio of 40 dB, an IIP3 of -5 dBm, and a sensitivity of -77 dBm for the Bluetooth mode when the losses from the external components are compensated. It consumes 42 mA in receive ${\pi}/4-diffrential$ quadrature phase-shift keying $({\pi}/4-DQPSK)$ mode of 8 Mb/s, 35 mA in receive GFSK mode of 1 Mb/s, and 32 mA in transmit mode from a 2.5-V supply. These results indicate that the architecture and circuits are adaptable to the implementation of a low-cost, multi-mode, high-speed wireless personal area network.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.26-35
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• 2007

We characterized the properties of the fabricated filter with the total internal reflection mirror (TIR) in the rectangular ring resonator and very small multimode interference (MMI) couplers on an InP material platform for photonic integrated circuits. Coupling power in and out of a resonator is increased by using an optimum MMI length of 110 ${\mu}m$ and a width of 9 ${\mu}m$, respectively. The semiconductor optical amplifier with the length of 120 ${\mu}m$ is integrated in the resonator to compensate the loss of the internal waveguide and the TIR mirror. A free spectral range of approximately 2 nm (244 GHz) is observed with an on-off ratio of 13 dB. The curve fitting also yields the power coupled per pass as 42%. To reach critical coupling at this coupling level would require a round trip loss of about 2.4 dB.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.7
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• pp.26-31
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• 2005

In this paper, a small BPF(band pass filter) is designed using new probe type for wireless communication system. The dielectric resonator is used high Q ceramics for low loss characteristic. In order to provide a band pass filter which can be reduced in dimension, can be reduced in height, and can be surface-mounted. The filter was fabricated using $TE_{01{\delta}}$ mode dielectric resonator. The input/output probes are attached to coner portion of the rectangular metal cavity. Results of the manufactured filter($12{\times}12{\times}8[mm]$) show that the center frequency is 9.95358[GHz], the insertion loss is -1.9[dB], the 3[dB]_bandwidth is 14.9[MHz], and the loaf Q is 664.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.963-967
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• 2001

The effects of the sintering additives such as Bi$_2$O$_3$and V$_2$O$_{5}$ on the microwave dielectric and sintering properties of ZnTiO$_3$system were investigated. Densities of >97% of the theoretical densities have been attained for ZnTiO$_3$at the sintering temperature range of 870~90$0^{\circ}C$ with Bi$_2$O$_3$and V$_2$O$_{5}$ additions of $_3$were obtained with 0.6wt% Bi$_2$O$_3$and 0.5wt% V$_2$O$_{5}$; Qxf$_{o}$ = 48,400 GHz, $\varepsilon$$_{r}$ = 22, and $\tau$$_{f}$ = -43 PPm/$^{\circ}C$. In order to improve temperature coefficient of resonance frequency, TiO$_2$was added to the above system. The optimum amount of TiO$_2$was 15mo1% when sintered at 87$0^{\circ}C$, at which we could obtain following results ; Qxf$_{o}$ = 44,700 GHz, $\varepsilon$$_{r}$ = 26, and $\tau$$_{f}$ = 0 ppm/$^{\circ}C$.EX>.>.EX>.>.>.EX>.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.561-565
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• 2002

The effects of sintering additives such as $Bi_2O_3$ and $V_2O_5$ on the microwave dielectric and sintering properties of (Zn, Mg)$TiO_3$ system were investigated. Highly dense samples were obtained for $(Zn_{0.8}Mg_{0.2})TiO_3$ at the sintering temperature range of $870{\sim}900^{\circ}C$ with $Bi_2O_3$ and $V_2O_5$ additions of <1wt.%, respectively. The microwave dielectric properties of $(Zn_{0.8}Mg_{0.2})TiO_3$ with 0.45 wt.% $Bi_2O_3$ and 0.55 wt.% $V_2O_5$ sintered at $900^{\circ}C$ were as follows: $Q{\times}f_o$=56,800 GHz, ${\varepsilon}_r$=22, and ${\tau}_f=-53ppm/^{\circ}C$. In order to improve temperature coefficient of resonant frequency, $TiO_2$ was added to the above system. The optimum amount of $TiO_2$ was 15 mol.% when sintered at $870^{\circ}C$, at which we could obtain following results: $Q{\times}f_o$ = 32,800 GHz, ${\varepsilon}_r$ = 26, and $\tau_f=0ppm/^{\circ}C$.

• ETRI Journal
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• v.26 no.4
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• pp.315-320
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• 2004

This paper proposes a 10-${\mu}m$ thick oxide layer structure that can be used as a substrate for RF circuits. The structure has been fabricated using an anodic reaction and complex oxidation, which is a combined process of low-temperature thermal oxidation (500 $^{\circ}C$ for 1 hr at $H_2O/O_2$) and a rapid thermal oxidation (RTO) process (1050 ${\circ}C$, for 1 min). The electrical characteristics of the oxidized porous silicon layer (OPSL) were almost the same as those of standard thermal silicon dioxide. The leakage current density through the OPSL of 10 ${\mu}m$ was about 10 to 50 $nA/cm^2$ in the range of 0 to 50 V. The average value of the breakdown field was about 3.9 MV/cm. From the X-ray photo-electron spectroscopy (XPS) analysis, surface and internal oxide films of OPSL prepared by a complex process were confirmed to be completely oxidized. The role of the RTO process was also important for the densification of the porous silicon layer (PSL) oxidized at a lower temperature. The measured working frequency of the coplanar waveguide (CPW) type short stub on an OPSL prepared by the complex oxidation process was 27.5 GHz, and the return loss was 4.2 dB, similar to that of the CPW-type short stub on an OPSL prepared at a temperature of 1050 $^{\circ}C$ (1 hr at $H_2O/O_2$). Also, the measured working frequency of the CPW-type open stub on an OPSL prepared by the complex oxidation process was 30.5 GHz, and the return was 15 dB at midband, similar to that of the CPW-type open stub on an OPSL prepared at a temperature of $1050^{\circ}C$ (1 hr at $H_2O/O_2$).

• Journal of Internet Computing and Services
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• v.21 no.2
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• pp.19-26
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• 2020

This paper analyses the feasibility of using implantable antennas to detect and monitor tumors. We analyze this setting according to the wireless propagation loss and signal fading produced by human bodies and their environment in an indoor scenario. The study is based on the ITU-R propagation recommendations and prediction models for the planning of indoor radio communication systems and radio local area networks in the frequency range of 300 MHz to 100 GHz. We conduct primary estimations on 915 MHz and 2.4 GHz operating frequencies. The path loss presented in most short-range wireless implant devices does not take into account the human body as a channel itself, which causes additional losses to wireless designs. In this paper, we examine the propagation through the human body, including losses taken from bones, muscles, fat, and clothes, which results in a more accurate characterization and estimation of the channel. The results obtained from our simulation indicates a variation of the return loss of the spiral antenna when a tumor is located near the implant. This knowledge can be applied in medical detection, and monitoring of early tumors, by analyzing the electromagnetic field behavior of the implant. The tumor was modeled under CST Microwave Studio, using Wisconsin Diagnosis Breast Cancer Dataset. Features like the radius, texture, perimeter, area, and smoothness of the tumor are included along with their label data to determine whether the external shape has malignant or benign physiognomies. An explanation of the feasibility of the system deployment and technical recommendations to avoid interference is also described.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.1
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• pp.20-26
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• 2016

This paper presents an X-band two-stage power amplifier using GaN-HEMT. Two-stage structure was adopted to take its high gain and simple inter-stage matching network. Based on a 3D EM simulation, the bond-wire inductance and the parasitic capacitance were predicted. By reducing bond-wire inductance, Q of the matching network is decreased and the bandwidth is improved. The implemented two-stage PA shows a power gain of more than 16 dB, saturated output power of more than 42.5 dBm, and a efficiency of more than 35 % in frequency range of 8.1~8.5 GHz with an operating voltage of 40 V.