• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.436-444
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• 2002

This paper presents a new method, which uses defected ground structure (DGS) on the ground planes of planar transmission lines such as microstrip and coplanar waveguide (CPW), to reduce the size of amplifiers. The main idea can be summarized as follow; DGS on the ground plane of microstrip or CPW line shows an increased slow-wave effect due to the additional equivalent L-C components. So the electrical length of the transmission line with DGS is longer than that of the standard transmission line for the same physical length. Then, the length of the transmission line with DGS can be shortened in order to maintain the original electrical length to be the same. This leads the matching of the original amplifier to be kept. In order to show the proposed method is valid, two kinds of amplifiers, the original amplifier and reduced amplifier, are fabricated, measured, and compared using both microstrip and CPW. The measured performances of the reduced amplifiers with DGS are quite similar to the ones of the original amplifiers for both microstrip and CPW amplifiers, even though the size of matching networks of the amplifiers with DGS are much smaller than those of the original amplifiers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.111-117
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• 2007

In this paper, a new marchand balun using broadside-coupled coplanar waveguide(CPW) on flexible printed circuit (FPC) is proposed. The proposed balun is designed based on the coupled line theory. The fabricated balun shows compact size and improved performance compared to the conventional microstrip line marchand balun. Measured amplitude and phase imbalance between the two balanced output ports are within 0.2 dB and $1^{\circ}$ respectively in a wide frequency range($1.63{\sim}3.44$ GHz). The proposed balun is expected to be used between various antennas and RF front-ends as a functional interconnection.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.9
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• pp.12-20
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• 2013

In this paper, a co-planar waveguide(CPW) fed zeroth-order resonant(ZOR) antenna with frequency reconfigurable radiating structures is fabricated and measured. The unit cell of proposed antenna consists of a series metal-insulator-metal(MIM) capacitor and two shunt line inductors which are shorted through the via. The proposed antenna is designed based on a composite right/left-handed(CRLH) transmission line with two unit cells and it has open ended structure in order to radiate electromagnetic energy mainly on the shunt arm. In order to reduce the antenna size and to exhibit a frequency reconfigurable ability using diode switches four straight strips bent by 90 degrees are used as shunt inductors. The total size of fabricated antenna is $0.22{\lambda}_0{\times}0.16{\lambda}_0$ at zeroth-order resonant(ZOR) frequency. The measured maximum gain and bandwidth (VSWR ${\leq}2$) are 3.1 dBi and 56MHz at ZOR frequency of 2.97 GHz, respectively. This type of antenna can be applied to a frequency reconfigurable antenna system with triple bands.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.9 s.112
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• pp.811-820
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• 2006

Ultra wideband CPW batons are proposed in this paper. The proposed talons are consisted of ultra wideband multi-stage Wilkinson dividers and 'X'-shaped $180^{\circ}$ out-of-phase generator. Bottom-bridges and via-holes are used to connect CPW ground lines instead of the conventional air-bridges which require troublesome manual working in fabrication with HMIC(Hybrid Microwave Integrated Circuits) substrates. The proposed CPW batons have ultra wideband of 3 or $10(=F_{figh}/F_{low})$ theoretically, the wideband characteristics and S-parameters of the basis Wilkinson divider are directly converted to those of the proposed batons. The proposed batons are so compact and small compared to the conventional Wilkinson batons because no additional area for out-of-phase section is required. So the size of the proposed batons is exactly the same as that of the basis Wilkinson dividers. As examples, 3-stage and 7-stage wideband Wilkinson dividers are converted to the proposed batons. Their measured operating bandwidth are $1\sim3GHz$ and $0.8\sim5GHz$, respectively, with excellent matching, isolation and power division performances. The measured magnitude and phase balance errors are ${\pm}0.5dB\;and\;0.45\;dB,\;and\;{\pm}5^{\circ}\;and\;{\pm}10^{\circ}C$ over $1\sim3GHz\;and\;0.8\sim5GHz$, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.12
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• pp.2773-2778
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• 2015

In this paper, the compact antenna with three folded patches for use in a number of bands of LTE, WCDMA, US-PCS, and WLAN at the same time is proposed. As the changes in widths of the 3 patches to widen the insufficient bandwidth are given, it is optimized for $S_{11}$<-6dB(VSWR<3). The CPW with a number of advantages is used in the proposed antenna. The proposed antenna is designed and fabricated with FR4 substrate to the size of $44.9{\times}35{\times}1mm^3$. Fabricated antenna has within $S_{11}$<-6dB under operating bands. And measured characteristics of radiation patterns and gains are shown under operating bands.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.5
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• pp.557-564
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• 2015

In this paper, the compact antenna for handsets is designed using FR-4 substrate for LTE(905-960 MHz), WCDMA(1922.8-2167.2 MHz), DCS(1710.2-1879.8 MHz), US-PCS(1850.2-1989.8 MHz), WLAN(2400-2483 MHz). The CPW line with many advantages and a spiral geometry for miniaturization is proposed. Widths of a spiral line are constant, and three stubs are added to broaden the bandwidth. Lengths and widths of three stubs are gradually changed. And proposed antenna is optimized for VSWR<3, designed, and fabricated. The dimension of this antenna is only $40{\times}30{\times}1mm3$ which is compact. It has been demonstrated by experiment that the compact planar antenna can be used as the mobile communication LTE antenna for 4G.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.57-60
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• 2002

In this paper, transmission lines with low and high characteristic impedance (Z$_{0}$) are fabricated and analyzed. The transmission lines are fabricated on the benzo-cyclo-butene (BCB) films of a low dielectric constant. For the low Z$_{0}$, two types of coplanar waveguide (CPW) structures are fabricated, which include bottom-ground and double-ground type. Measurement shows that Z$_{0}$ values for each CPW type are 7.3 and 9.4$\Omega$, respectively, at a signal line width of 100 #m. Whit the ratio between the spacing of bottom-ground and the signal line with becomes greater than 2.5, the Z$_{0}$ is nearly saturated. In addition, thin film microstrip lines fabricated using the BCB insertion layers show very low Z$_{0}$ of 25.5$\Omega$, and this impedance is ~64 % of the values obtained from the BCB-based CPW structures of the same line width. Measurement result of CPW on BCB layer is 100.5 Ω.s 100.5 Ω.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.537-543
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• 2010

This paper presents a slot-shaped defected ground structure(DGS) which has multi-band rejection property. The proposed structure, in which the spiral slot-shaped defects with different size are aligned in the transverse direction to the guiding direction of the coplanar waveguide(CPW), provides multiple resonance frequencies. Compared with the simulated results, the band rejection characteristic is in good agreement with the measurement. Also, an equivalent circuit model of the proposed structure is presented, where the DGS on the ground plane is modeled as LC-resonators. This resonators are inductively coupled to the signal line through mutual inductance. From the equivalent circuit model, multi-band rejection property was derived.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1086-1098
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• 2005

Two types of small wideband antennas are proposed for UWB application. One type is small biconical structure fed by coaxial probe, which is easy to be installed on the circuit board. The other type is of planar bow-tie type fed by coplanar transmission line. Generally, the bandwidth of the latter type is significantly narrower than that of the former type. It is shown, however that the bandwidth of the latter type can be made to be comparable to that of the former, if some series inductive component is introduced in the center conductor line in the CPW transmission line by replacing some part of center line with narrower line of higher characteristic impedance. The series inductance component play an important role of neutralizing the capacitive component of the small bow-tie antenna, thereby making broadband impedance matching possible. The small planar bow-tie antenna was fabricated and experimented. The experimental results for return loss are observed to be in good agreement with simulated results. The radiation pattern is also investigated experimentally.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.11
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• pp.12-17
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• 1999

In this paper, we proposed a novel CB-CPW(Conductor Backed CPW) for suppression of crosstalk caused by PPL(Parallel Plate Line) mode in the millimeter wave frequency. The proposed structure is formed by the GaAs main substrate attached on the Si lossy layer. The PPL mode can be suppressed by the Si lossy layer of conductivity ${\sigma}$, and it reduces the crostalk between the nearby transmission lines. Using 200 um thick Si substrate of ${\sigma}$ = 30S/m, as the lossy layer, the crosstalk can be suppressed below - 40 dB at 60 GHz. The proposed method is costly effective because inexpensive Si wafer is employed to suppress the PPL mode, and it can be used in the various types of millimeter wave applications.