• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.852-857
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• 2011

In this paper, the application of a variable characteristic impedance transmission line that can be used to design a dual-band bandpass filter(BPF) is presented. The proposed filter offers a fixed first frequency passband and a controllable second passband. The tuning of the second passband is achieved by varying the characteristic impedance of and open shunt stub line in a stub loaded resonator(SLR) with the help of a defected ground structure(DGS) transmission line and varactor diodes. In order to validate the proposed structure, a two stage dual-band BPF with three transmission zeros was implemeted and experimentally verified based on its theoretical predictions and simulations.

• Journal of Digital Convergence
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• v.12 no.4
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• pp.343-348
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• 2014

This paper suggested a theoretical approach and an implementation for the design of an unequal Wilkinson power divider with a high dividing ratio operating at two-frequencies. The T-section transmission lines and the two-section of Monzon's theory are proposed to operate a dual-band application. To achieve the high dividing ratio divider, the high impedance line using a T-shaped structure and low impedance lines with periodic shunt open stubs are implemented. For the validation of this divider, a dual-band power divider with a high dividing ratio of 5 is simulated and measured at 1 GHz and 2 GHz. The measured performances of the divider are in good agreements with simulation results.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.63-63
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• 2018

본 연구는 플라즈마 전해 산화 (PEO) 및 RF (Radio Frequency) 스퍼터링을 이용한 2 단계 접근법에 의해 처리 된 MgO / Ni-Cr의 고내식성 이중층 코팅을 제조하기 위해 수행되었다. 이를 위해 $100mA/cm^2$ 교류 조건에서 180 s PEO를 한 후 150W 에서 900s RF 스퍼터링을 수행 하였다. 코팅의 형태는 주사전자현미경(SEM)을 사용하여 관찰되었으며 코팅의 상조성은 X-선 회절(XRD) 및 X-선 광전자 분광법(XPS)을 사용하여 분석하였다. SEM 이미지는 스퍼터링 된 Ni-Cr이 크랙의 대부분과 미세한 미세 공극을 덮어 코팅 결함이 감소함을 보여 주었다. 따라서, 코팅 된 샘플의 거칠기 값은 스퍼터링 공정 후에 감소되었다. 단면 이미지로부터, 스퍼터링된 코팅층은 낮은 두께 때문에 거의 검출되지 않았다. EDS, XRD 및 XPS를 사용한 조성 분석은 금속 상태의 형태로 Ni 및 Cr 존재를 나타내었고 XPS에서 NiCr2O4 부동태 피막이 검출되었다. MgO / Ni-Cr 이중층 코팅의 내부식성은 MgO / Ni-Cr 이중층을 가진 샘플의 금속 원소와 비교하여 우수한 부식 특성을 나타내는 전위 역학적 분극 시험 및 전기 화학적 임피던스 분광법으로 평가 하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1049-1056
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• 2017

In this paper, a microstrip-fed dual-band monopole antenna with two arc-shaped lines for WLAN(: Wireless Local Area Networks) applications was designed, fabricated and measured. The proposed antenna is based on a microstrip-fed structure, and composed of two arc-shaped lines and then designed in order to get dual band characteristics. We used the simulator, Ansoft's High Frequency Structure Simulator(: HFSS) and carried out simulation about parameters L2, L5, and with/without slit to get the optimized parameters. The proposed antenna is made of $13.0{\times}34.0{\times}1.0 mm^3$ and is fabricated on the permittivity 4.4 FR-4 substrate($12.0{\times}34.0{\times}1.0mm^3$). The experiment results are shown that the proposed antenna obtained the -10 dB impedance bandwidth 360 MHz (2.29~2.65 GHz) and 1,245 MHz (4.705~5.95 GHz) covering the WLAN bands. Also, the measured gain and radiation patterns characteristics of the proposed antenna are presented at required dual-band(2.4 GHz band/5.0 GHz band), respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.245-252
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• 2010

This paper proposes an improved filter synthesis method for dual-band filters based on coupled lines loaded with shunt stubs. The conventional design method relies on equality of the response of the conventional single-band filter and its dual-band counterpart at two frequencies. On the other hand, the proposed method is based on equivalence of the propagation constants and the image impedances of the two filters. Therefore, the proposed method does not suffer from bandwidth reduction phenomena, which requires complex compensating process in the conventional method. Also, the alternative design parameters provided by the demonstrated method enable to construct dual-band filters with more flexibility. For experimental verification, a Chebyshev type dual-band filter with center frequencies at 1 GHz and 3.5 GHz is designed and fabricated. The measured results are in excellent agreement with the full-wave simulated results.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.4
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• pp.441-448
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• 2015

In this paper, a CPW-fed dual-band monopole antenna with two branch strips for WLAN(Wireless Local Area Networks) applications was designed, fabricated and measured. The proposed antenna is based on a CPW-feeding structure, and composed of two branch strips and then designed and tuned the length of two branch lines to obtained required frequencies bands. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and carried out simulation about parameters $L_5$, $L_8$, $W_3$, $W_5$, $W_9$. The proposed antenna is fabricated on the FR-4 substrate using the obtained parameters. The numerical and experiment results demonstrated that the proposed antenna obtained the -10 dB impedance bandwidth 1,095 MHz (1.57~2.665 GHz) for 2.4 GHz band and 1,680 MHz (4.99~6.67 GHz) for 5 GHz band satisfied requirement while simultaneously covering the WLAN bands. And characteristics of gain and radiation patterns are determined for WLAN operating bands.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.2
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• pp.135-140
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• 2008

In this paper, the spiral antenna with the center frequencies of 315MHz, 433MHz, and 447MHz for RKE system of a vehicle is designed on PCB. The antenna is microstrip line-fed, and applied PIFA concept near the feeding part to easily tune center frequency and input impedance. The PIFA-type spiral antenna with the size of $30mm{\times}20mm$ is designed on printed PCB by considering the effect of circuits and components on PCB, ECU case and vehicle body. Also chip inductor inserted dual-band spiral antenna of 315MHz and 447MHz is designed. We found that the antenna designed on PCB satisfied the antenna specifications through measurement and field test.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.5
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• pp.444-449
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• 2009

This paper presents the design of a dual band branch line hybrid coupler(BLHC) with different power division ratios at two bands. In the proposed design, transmission lines of the BLHC are transformed to $\pi$-type equivalent circuits which represent different impedances and $\lambda/4$ electrical length at two frequency bands. In order to verify the proposed method, a dual band coupler with different power division ratios is designed for 0.9 GHz and 2 GHz applications. The desired power division ratios are 1:1 and 1:3 at the two operating frequency bands. The measured results show excellent performance with an insertion loss of less than 0.33 dB, a return loss of less than -18.07 dB, and good isolation characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1291-1298
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• 2007

A novel 1:4 unequal wilkinson power divider using rectangular-shaped defected ground structure(DGS) in double layered substrate is proposed for removing the ground problem of DGS in packaging. Rectangular-shared DGS produces the transmission line having much higher characteristic impedance than standard microstrip line. The proposed unequal divider is composed of DGS and double layered substrate in order to be free from the ground problem of DGS patterns in packaging in metal housings. The second substrate is attached to the first substrate which contains DGS pattern on its ground plane at the bottom side to form the double layered substrate. In order to show the validity of the proposed DGS in the double layered substrate, a 1:4 unequal power divider is designed and measured. The predicted and measured performances are shown with an excellent agreement between them.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1206-1211
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• 2006

In this paper, a Balun-BPF with the balun and BPF characteristics is proposed by using dual-mode ring resonator of $1{\lambda}$. We obtained the property of balun with the phase imbalance by symmetrically placing each output of ring resonator. The dual mode has been made by impedance difference between input and output lines. The fabricated Balun-BPF shows bandwidth of 40 MHz and insertion loss of 2.4 dB at a center frequency of 2.45 GHz. It shows the phase imbalance of $180{\sim}184$ degree and the magnitude imbalance of within 1 dB. The measured frequency responses agree well with simulated ones.