• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.688-693
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• 1999

This paper presents a very simple coupled line structure for MMIC which uses stacked microstrip line and does not employ any dielectric process step. For the analysis and optimization of these coupled line structure, HP-Momentum was used. The measured performance of 3 dB coupler shows 23 to 45 GHz broadband characteristics. Additionally, a balanced 2-stage Ka-Band power amplifier which uses the proposed 3 dB coupler, was also fabricated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.2
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• pp.136-145
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• 2002

In this paper, we facilitate the analysis of 1D PBG structure using a ABCD matrix formulation after converting field parameters into circuit parameters. Dispersion diagrams for an infinite 1D PBG structure are derived and compared with the frequency responses for a finite structure (N=10). When the proposed method is adopted, the analysis and synthesis of 1D PBG structures become very convenient.

• Journal of electromagnetic engineering and science
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• v.13 no.4
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• pp.214-223
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• 2013

This paper proposes a theoretical analysis of hidden device detection and a design of multiband circular polarization patch array antenna for non-linear junction detector system application. A good axial ratio of circular polarization patch antenna is realized by a new approach that employs inclined slots, two rectangular grooves and a truncated ground for the conventional antenna. A good axial ratio of the 1.5 dB lower is measured by having an asymmetric gap distance between the ground planes of the coplanar waveguide feeding structure. The common ground plane of the linear array has an optimum trapezoidal slot array to reduce the mutual coupling without increasing the distance between the radiators. The higher gain of about 1 dBi is realized by using the novel common ground structure. The measured return loss, gain, and axial ratio of the proposed single radiator, as well as the proposed array antennas, showed a good agreement with the simulated results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.1-6
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• 2002

This paper presents that photonic bandgap structures suppressing the propagation of surface waves can improve the performance of the patch antennas on a thick and high dielectric constant substrate. The forbidden propagation of surface wave due to the photonic bandgap enhances the radiation efficiency and reduces the back radiation drastically.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.5
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• pp.430-433
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• 2017

This paper presents a S/C/X-band LNA MMIC with resistive feedback structure in 0.25 um GaN HEMT process. The GaN devices have advantages as a high output power device having high breakdown voltage, energy band gap and stability at high temperature. Since the receiver using the GaN device with high linearity can be implemented without a limiter, the noise figure of the receiver can be improved and the size of receiver module can be reduced. The proposed GaN LNA MMIC based on 0.25 um GaN HEMT device is achieved the gain of > 15 dB, the noise figure of < 3 dB, the input return loss of > 13 dB, and the output return loss of > 8 dB in the S/C/X-band. The current consumption of GaN LNA MMIC is 70 mA with the drain voltage 20 V and the gate voltage -3 V.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.4
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• pp.369-376
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• 2003

In this paper, Ka-Band NRD guide band pass filter with newly designed inductive post structure is proposed and analyzed with its test results. Generally, millimeter-wave filters are very sensitive in their physical dimensions, hence, it is requires extreme precisions of several micron so as to get the designed performance. In case of common NRD Guide filter with air gap coupled structure, it is fabricated with dielectric blocks coupled via air gap. In these structures, however, it was not easy to fabricate and to process of each NRD guide dielectric resonator blocks using PTFE, so it was almost impossible to assemble with several microns in precision. In this our research, however, each dielectric resonators are coupled with a pair of inductive metal post, so all resonators are located in a single NRD Guide. The dielectric parts between two pairs of posts are operated as resonators of each stage, and the positions of the post decide the couplings between resonators. The structure we suggested is suitable fur mass production, because it is very simple and easy to process. As a result of measurements, designed NRD guide inductive post filter has a superior performance. The center frequency is 39.475 GHz with 350 MHz bandwidth, insertion loss is less than 1.8 dB, and the return loss is below than -18 dB.

• Progress in Superconductivity and Cryogenics
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• v.16 no.1
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• pp.1-5
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• 2014

We calculated the resonance tunneling energy band in the BCS gap for Type-II superconductor in which periodic potential is generated by external magnetic flux. In this model, penetrating magnetic flux was assumed to be in a fixed lattice state which is not moving by an external force. We observed the existence of two subbands when we used the same parameters as for the $Nd_{1.85}Ce_{0.15}CuO_X$ thin film experiment. The voltages at which the regions of negative differential resistivity (NDR) started after the resonant tunneling ended were in a good agreement with the experimental data in the field region of 1 T - 2.2 T, but not in the high field regions. Discrepancy occurred in the high field region is considered to be caused by that the potential barrier could not be maintained because the current induced by resonant tunneling exceeds the superconducting critical current. In order to have better agreement in the low field region, more concrete designing of the potential rather than a simple square well used in the calculation might be needed. Based on this result, we can predict an occurrence of the electromagnetic radiation of as much difference of energy caused by the 2nd order resonant tunneling in which electrons transit from the 2nd band to the 1st band in the potential wells.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1519-1526
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• 2023

For the first time Aluminium-BariumeZinc oxide nanocomposite (ZABONC) was synthesized by solution combustion method where calcination was carried out at low temperatures (600℃) to study the electromagnetic (EM) (X/γ) radiation shielding properties. Further for characterization purpose standard techniques like PXRD, SEM, UV-VISIBLE, FTIR were used to find phase purity, functional groups, surface morphology, and to do structural analysis and energy band gap determination. The PXRD pattern shows (hkl) planes corresponding to spinel cubic phase of ZnAl₂O4, cubic Ba(NO₃)₂, α and γ phase of Al₂O₃ which clearly confirms the formation of complex nano composite. From SEM histogram mean size of nano particles was calculated and is in the order of 17 nm. Wood and Tauc's relation direct energy band gap calculation gives energy gap of 2.9 eV. In addition, EM (X/γ) shielding properties were measured and compared with the theoretical ones using standard procedures (NaI (Tl) detector and multi channel analyzer MCA). For energy above 356 keV the measured shielding parameters agree well with the theory, while below this value slight deviation is observed, due to the influence of atomic/crystallite size of the ZABONC. Hence synthesized ZABONC can be used as a shielding material in EM (X/γ) radiation shielding.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.443-451
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• 2010

This paper describes a fully integrated CMOS low-IF mobile-TV RF tuner for Band-III T-DMB/DAB applications. All functional blocks such as low noise amplifier, mixers, variable gain amplifiers, channel filter, phase locked loop, voltage controlled oscillator and PLL loop filter are integrated. The gain of LNA can be controlled from -10 dB to +15 dB with 4-step resolutions. This provides a high signal-to-noise ratio and high linearity performance at a certain power level of RF input because LNA has a small gain variance. For further improving the linearity and noise performance we have proposed the RF VGA exploiting Schmoock's technique and the mixer with current bleeding, which injects directly the charges to the transconductance stage. The chip is fabricated in a 0.18 um mixed signal CMOS process. The measured gain range of the receiver is -25~+88 dB, the overall noise figure(NF) is 4.02~5.13 dB over the whole T-DMB band of 174~240 MHz, and the measured IIP3 is +2.3 dBm at low gain mode. The tuner rejects the image signal over maximum 63.4 dB. The power consumption is 54 mW at 1.8 V supply voltage. The chip area is $3.0{\times}2.5mm^2$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.10 s.113
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• pp.935-942
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• 2006

In this paper, a novel theory of realizing the series capacitor with broadside coupled suspended substrate stripline (BCSSS) is proposed. The proposed theory is relatively simple because the method of odd mode analysis is only applied: However, this theory supplies reliable result by considering the line effective width and end effect caused by the fringing field. The simulation results are presented to compare and analyze the characteristics of the ideal lumped capacitor and the coupled line capacitor. Also, the capacitive gap coupled line band-pass filter based on the proposed theory are designed and fabricated. The results prove successfully the validity of the proposed theory.