• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.374-383
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• 2013

This paper presents a design for improvement of isolation characteristics by the inserted stub structure on ground plane of a handy terminal which is composed of a main antenna and a sub antenna covered LTE bandwidth. In order to compensate for a resonance length of proposed antenna and to realize a high isolation characteristic, a pair of stub was inserted and located on ground plane that currents from two antennas were converged. A simulated isolation characteristic of antenna without stub at the LTE class 13 band was about -5 dB, but its characteristics of proposed antenna with two stubs at uplink(777~787 MHz) and downlink(746~756 MHz) of the LTE class 13 band were about -12 dB and -15 dB, respectively. An average gain of a fabricated antenna with two stubs was observed about -2 dBi above and it showed good results with comparison of business condition that the average gain of commercial handy terminal has to appear -4 dBi above. The measured S-parameter characteristics and radiation patterns showed a reasonable agreement with the simulation results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2269-2274
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• 2015

In this paper, the reduced size in horizontal sizes of the narrow band pass filter (BPF) with λg/4 short stub using S shaped folded coupling structure is presented. This BPF with narrow bandwidth show flexible bandwidth with variation of the position of the stubs using the Qe(external quality factor) without changing the impedance value. On the other hand, by replacing the horizontal quarter-wavelength transmission lines with the equivalent S shaped coupled line, the BPF with reduced the size of horizontal can be realized. The proposed BPF shows the insertion loss of 1.46 dB and the return loss of 16.5 dB with bandwidth of 3.4 % at the center frequency of 5.8 GHz, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1107-1116
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• 2007

In this paper, a broadband open stubs band pass filters which can suppress the second harmonics using Z-transform technique, is designed, fabricated and characterized. The proposed broadband filters integrate the band stop filter with the FSCS structure and ${\lambda}_g/4$ open stub in order to suppress the second harmonics. Due to insertion of BSF at input and output terminal, the size of the filter was increased in the conventional filter, however, in the proposed structure, the position of inverter that connects the stubs can be integrated between those stubs, thereby decreasing the size. So, it can be fabricated in the size of $18.7{\times}16.9mm^2$ which is smaller size than conventional one. The measured results of the proposed filters have center frequency of a 5.8 GHz with bandwidth of 95 %, insertion loss of 0.6 dB, return loss of 14 dB. The simulation results are consistent with measurement results. The filter is designed far X-band satellite communication and ITS applications.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.35-42
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• 2012

An inductive loaded microstrip patch antenna using aperture coupled feeding is designed and an impedance bandwidth enhancement method using a shunt stub is investigated. The -10 dB impedance bandwidth of the AIMPA with a shunt stub is increased up to about 5.51 %. The impedance bandwidth of the corresponding AIMPA without a shunt stub is 2.4 %. The increase of the impedance bandwidth of the AIMPA with a shunt stub is about 129.6 % compared to that of the corresponding AIMPA without a shunt stub.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.439-444
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• 2020

In this paper, the analysis of the FSCS (frequency-selected coupling structure) as the coupling coefficient and multi-stage FSCS for enhanced bandstop bandwidth is suggested. The FSCS is composed by the connected coupled-line and open-stub. Basically, the resonance frequency of the FSCS is given by the electrical length of the stub, and the bandwidth is controlled by the coupling coefficient. Multi-stage FSCS is made by addition of another FSCS with the half electrical length. Manufactured bandstop filter using 3 stage FSCS is measured with the stopband of 177.3% and the maximum return loss of 1dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.2
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• pp.39-49
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• 2012

An impedance bandwidth enhancement method of an aperture coupled microstrip patch antenna (ACMPA) using a shunt stub is investigated. The conventional ACMPA with a H-shaped coupling aperture is designed and the electrical parameters for the equivalent circuit of the designed conventional ACMPA are extracted. A method for the enhancement of the impedance bandwidth of the ACMPA using a tuning stub connected in shunt with the feed line is presented. The -10 dB return loss impedance bandwidth of the ACMPA with a shunt stub is increased up to about 14 %. The maximum impedance bandwidth of the corresponding ACMPA without a shunt stub is 5.4 %. The increase of the impedance bandwidth of the ACMPA with a shunt stub compared to that of the corresponding ACMPA without a shunt stub is about 160 %.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.6 s.121
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• pp.674-679
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• 2007

In this paper, the size of the dual-mode microstrip ring resonator is reduced by adding four open stubs, and bandpass filters having 100 MHz bandwidth are designed at the center frequency of 2 GHz. The size of the ring resonator can be controlled by varying the capacitance of the stubs, and the bandpass filter can be designed in two cases, which are two combinations of the stubs. Two bandpass filters are designed and fabricated by using the two-stage bandpass filter circuit model of the proposed structure, and the measured results show good agreement with the simulated results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.12
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• pp.115-124
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• 2004

In this paper, we introduce the advanced compact transmission line with periodic stepped stubs. They are more effective than normal stubs in ATL. The short stepped stubs loading of transmission line work as effective shunt capacitance and that was proved by equivalent circuit based on transmission line theory and quasi-static analysis. And the compact branch-line coupler and the compact rat-race coupler via proposed compact microstrip line were designed at 1.8 ㎓. They have 677 ㎟ and 913 ㎟, respectively, and they are 62% and 45% of normal design.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.97-102
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• 2008

A new internal antenna for GSM/DCS/Bluetooth application is proposed by using a folded loop resonator. Both feed leg and shorting leg are symmetrically implemented at the center of the folded loop, thus leading to produce resonances at integer frequencies of quarter wavelength. An open stub added at one end of the folded loop can reduce resonant frequencies. The open stub play a role in generating PIFA structure at a GSM band, thus increasing bandwidth, Two resonances at the GSM band are observed at folded ring and PIFA, respectively.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.6
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• pp.97-102
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• 1985

A new microwave transmission line frequency discriminator in MIC is described, which is composed of a branch-line hybrid 3dB coupler, a λ/2-short stub and a λ/4-opcn stub. It is experimentally verified that the discriminator is linear in a 400 MHz bandwidth at center frequency 4.94 GHz and has return loss more than 15dB in that range.