• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.101-103
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• 2018

This paper describes -40kV high voltage solid state pulse power modulator (SSPPM) for driving a magnetron, which is used as a RF power source of LINAC for cancer treatment systems. In case of the medical LINAC, small size and light weight are required. The SSPPM is 92 liters in size and weighs 50 kg. In this paper, S-band 2.6 MW magnetron load experiment is conducted and impedance matching was applied to obtain a smooth output current. Finally, the experimental results is discussed and the reliability of SSPPM is verified.

• Journal of information and communication convergence engineering
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• v.16 no.4
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• pp.203-212
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• 2018

In this article, a novel design of patch antenna with wide band characteristics is presented. The proposed antenna is having electrical dimensions of $0.14{\lambda}{\times}0.11{\lambda}$ (at lower initial frequency) and footprints of $150mm^2$. Structural parameters optimization shows 3.1-23.5 GHz frequency range for a (reflection coefficient) $S_{11}{\leq}-10dB$ and simulated gain 6.8 dB is obtained. An equivalent circuit model is proposed to get an insight view of antenna. Advanced Systems Design (ADS) simulation results are obtain which confirm the validity of proposed model. Degenerated foster canonical form has been used to explain the reactance and capacitive behavior idea of simulated proposed antenna's input impedance later on an equivalent circuit model and smith chart is also suggested. HFSS and CST have been used to analyze antenna behavior. The proposed antenna can be further used for microwave image detection applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.290-298
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• 2018

Herein, an S-band internally-matched power amplifier that shows a power capability of 300 W in a Long Term Evolution(LTE) band 7 is designed and fabricated using a CGHV40320D GaN HEMT from Wolfspeed. Based on the nonlinear model, the optimum source and load impedance are extracted from the source-pull and load-pull simulations at the fundamental and harmonic frequencies, and the harmonic impedance tuning circuits are implemented inside a ceramic package. The internally matched power amplifier, which is fabricated using a thin-film substrate with a high relative permittivity of 40 and an RF35TC PCB substrate, is measured at the pulsed condition with a pulse period of 1 ms and a duty cycle of 10%. The measured results show a maximum output power of 257~323 W, a drain efficiency of 64~71%, and a power gain of 11.5~14.0 dB at 2.62~2.69 GHz. The LTE-based measurement shows a drain efficiency of 42~49% and an ACLR of less than -30 dBc(excluding 2.62 GHz) at an average power of 79 W.

• Journal of Korean Neurosurgical Society
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• v.48 no.3
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• pp.240-243
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• 2010

Objective : Radiofrequency (RF) medial branch neurotomy is an effective management of lumbar facet syndrome. However, pain may recur after period of time. When pain recurs, it can be repeated, but the successful outcome and duration of relief from repeated procedures are not clearly known. The objective of this study was to determine the success rate and duration of pain relief from repeated radiofrequency medial branch neurotomy for lumbar facet syndrome. Methods : A retrospective review of medical records was done on 60 consecutive patients, from March of 2006 to February of 2009, who had an initial successful RF neurotomy but subsequently underwent repeated procedures due to recurrence of pain. All procedures were done in carefully selected patients after at least two responsive medial branch nerve blocks. C-arm fluoroscopic guide, impedance, sensory and motor threshold monitoring tools were used for the precise placement of electrodes. Responses of repeated procedures were compared with initial radiofrequency neurotomy for success rates and duration of pain relief. Results : There were 48 females and 12 males. Mean age was 52.4 years (range, 26-83). RF medial branch neurotomy was done on one side in 38 and both sides in 22 patients, each covering at least three segments. Average visual analog scale at last procedure was 6.8. Twelve patients had previous lumbar operations, including 4 patients with instrumentations. Fifty-five patients had two procedures and five patients had three procedures. Mean duration of successful pain relief (> 50% of previous pain for at least 3 months period) after initial radiofrequency neurotomy was 10.9 months (range, 3-28) in 51 (85%) patients. From repeated procedures, successful pain relief was seen in 50 (91%) patients with average duration of 10.2 months (range, 3-24). Five patients had third procedure, which was successful in 4 (80%) patients with mean duration of 9.8 months (range, 5-16). This was not statistically different from initial results. There were no permanent neurological complications from the procedures. Conclusion : Results of this study indicate that the frequency of success and durations of relief from repeated RF medial branch neurotomy for lumbar facet syndrome are similar to initial results that provided relatively prolonged period of pain relief without major side effects Each procedure seems to provide successful pain relief for about 10 months in more than 85% of carefully selected patients when properly done.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.5 s.96
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• pp.511-517
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• 2005

Many cellular phone volunteer studies have been conducted since such a social issue is raised that the long time usage of cellular phone by teenagers may increase health risk. While there were various adult volunteer studies using GSM cellular phone on heart rate and blood pressure, very few teenager studies using CDMA phone were conducted. In this study, two volunteer groups of 21 teenagers and 21 adults were exposed to 300 mW CDMA wave for half an hour, and the physiological parameters such as blood pressure, heart rate, respiration rate, and skin impedance were investigated. All the parameters fur both groups were unaffected during exposure except the skin impedance of teenager group.

• Progress in Superconductivity and Cryogenics
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• v.16 no.3
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• pp.21-25
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• 2014

As wireless power transfer (WPT) technology using strongly coupled electromagnetic resonators is a recently explored technique to realize the large power delivery and storage without any cable or wire, this technique is required for diffusion of electric vehicles (EVs) since it makes possible a convenient charging system. Typically, since the normal conducting coils are used as a transmitting coil in the CPT system, there is limited to deliver the large power promptly in the contactless EV charging system. From this reason, we proposed the combination CPT technology with HTS transmitting antenna, it is called as, superconducting contactless power transfer for EV (SUWPT4EV) system. As the HTS coil has an enough current density, it can deliver a mass amount of electric energy in spite of a small scale antenna. The SUCPT4EV system has been expected as a noble option to improve the transfer efficiency of large electric power. Such a system consists of two resonator coils; HTS transmitting antenna (Tx) coil and normal conducting receiver (Rx) coil. Especially, the impedance matching for each resonator is a sensitive and plays an important role to improve transfer efficiency as well as delivery distance. In this study, we examined the improvement of transmission efficiency and properties for HTS and copper antennas, respectively, within 45 cm distance. Thus, we obtained improved transfer efficiency with HTS antenna over 15% compared with copper antenna. In addition, we achieved effective impedance matching conditions between HTS antenna and copper receiver at radio frequency (RF) power of 370 kHz.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.344-348
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• 2011

A layer of $TiO_2$ thin film less than ~200nm in thickness, as a blocking layer, was deposited by 13.56 MHz radio frequency magnetron sputtering method directly onto the anode electrode to be isolated from the electrolyte in dye-sensitized solar cells (DSCs). This is to prevent the electrons from back-transferring from the electrode to the electrolyte ($I^-/{I_3}^-$). The presented DSCs were fabricated with working electrode of F:$SnO_2$(FTO) glass coated with blocking $TiO_2$ layer, dye-attached nanoporous $TiO_2$ layer, gel electrolyte and counter electrode of Pt-deposited FTO glass. The effects of blocking layer were studied with respect to impedance and conversion efficiency of the cells. The, electrochemical impedances of DSCs using this electrode were $R_1$: 13.9, $R_2$: 15.0, $R_3$: 10.9 and $R_h$: $82{\Omega}$. The $R_2$ impedance related by electron movement from nanoporous $TiO_2$ to TCO showed lower than that of normal DSCs. The photo-conversion efficiency of prepared DSCs was 5.97% ($V_{oc}$: 0.75V, $J_{sc}$: 10.5 mA/$cm^2$, ff: 0.75) and approximately 1% higher than general DSCs sample.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.87-92
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• 2022

In this paper, a study was conducted on the design of an array element that can be applied to the AESA radar for seeker. An antenna for application to AESA radar should choose an optimal radiation element to be applied to an array antenna in order to secure electronical beam steering characteristics, and consider beam steering characteristics when designing. In particular, in order to satisfy the wide-angle beam steering characteristics, the wide-angle impedance matching technique should be used to minimize the scan blindness region that may occur during wide-angle steering. As such, securing the stability of system operation is becoming an important design consideration for AESA radar. In this paper, WAIM is applied to the end of the radiation element to improve the characteristics of the radiation element applied to the AESA radar antenna device, and the change in the performance of the active reflection coefficient, which is a stable operation index of the system, is reviewed. The final performance result verified the validity of the proposed method by mathematically synthesizing the simulation data.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.12
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• pp.77-84
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• 2007

In this parer, a wideband low-noise amplifier (LNA) has been realized in a 0.18mm CMOS technology for the applications of subsampling direct-conversion RF receivers. By exploiting the inverter-type transimpedance input stage with a 3rd-order Chebyshev matching network, the wideband LNA demonstrates the measured results of the -3dB bandwidth of 5.35GHz, the power gain (S21) of $12\sim18dB$, the noise figure (NF) of $6.9\sim10.8dB$, and the broadband input/output impedance matching of less than -10dB/-24dB within the bandwidth, respectively. The chip dissipates 32.4mW from a single 1.8V supply, and occupies the area of $0.56\times1.0mm^2$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1223-1232
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• 2008

In this paper, an analytic method is proposed to extract the reference slot admittance required for the design of a non-resonant waveguide edge slot array. A slot and two neighboring transmission line sections of the numerous alternately inclined slots with the identical inclination angle are modelled as a uniform lossy transmission line, and thus, the total ABCD matrix is easily calculated and compared with the simulated or measured one. From this procedure, the complex characteristic impedance and the complex propagation constant of the lossy transmission line are calculated and the normalized slot admittance is analytically obtained. In order to validate the proposed method, the admittance value of a reference slotted waveguide fabricated for designing the X-band edge slot array is extracted and it is compared with the one obtained by the other conventional method.