• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.471-472
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• 2015

In this paper, a design method for enhancing the gain of a series-fed dipole pair (SDP) antenna using mutiple directors is studied. Strip-type directors are located above the second dipole of the SDP antenna, and the variations of the input VSWR bandwidth and gain depending on the length of the second dipole and the number of directors are analyzed. The antenna is optimized to obtain gain > 8 dBi in the frequency range of 1.7-2.7 GHz, which has three directors in the optimum design. The optimized antenna is designed on an FR4 substrate with a dimension of 86.2 mm by 152.3 mm, and it has frequency bands of 1.67-2.79 GHz for a VSWR < 2 and 1.69-2.72 GHz for a gain > 8 dBi.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.636-644
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• 2009

This paper presents a compact, low insertion loss, sharp rejection and wide band microstrip band pass filter that is composed rectangular loop resonator and step-impedance-open-stub(SIOS) for wireless data communication. The SIOS can be reduce length about 30% more than general $0.25{\lambda}$ stub. And the stub can the advantage of tuning impedance magnitude. In order to demonstrate agrement of this paper prove, the optimized wide band pass filters are realized and experimented. A transmission line model used to calculate the frequency response of the new filters shows good agreement with measurements. The filter has 3dB fractional bandwith of 52.5%(3.267GHz), an insertion loss of better than 0.33dB from 4.587GHz to 7.854GHz, and two rejection of greater than 30dB within 221MHz$(4.366GHz{\sim}4.587GHz)$ at low frequency band, 181MHz$(7.854GHz{\sim}8.035GHz)$ at high frequency band. Maximum rejection characteristics of the filter are -54dB at low frequency and -60dB at high frequency.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.2
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• pp.113-118
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• 2007

KPCS internal antenna in this paper, is designed and fabricated using the theory based on the folded monopole antenna. I propose folded monopole internal antenna which has high gain low profile structure with easy installation into the handset of mobile phone. Design frequency is 1.8 GHz that is a center frequency of Korea PCS frequency band, and the impedance variances due to change of antenna structure as a length and width are simulated. Measurements show that input VSWR range under 2:1 is 1.72 - 1.88 GHz, and radiated H-plane pattern is omnidirectional under passive state. Active sensitivities and output power of phone applied antenna are $-105\;{\sim}\;-108\;dBm$ and $22.5\;{\sim}\;23.6\;dBm$ max., respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.5
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• pp.452-461
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• 1997

In this paper, we present a computer-aided design(CAD) technique for minimizing the phase shift in microstrip PIN diode attenuators due to the junction capacitance in the equivalent circuit model of PIN diode. Microstrip PIN diode attenuators use the characteristics which the reactance of microstrip line changes from inductive to capacitive as the frequency sweeps across the band. Microstrip PIN diode attenuator designed utilizes the quarter-wavelength transmission line terminating with the half-moon radial stub, which is designed for negligible phase shifting effect over the intersted bandwidth. The attenuator has similar phase shift at 0 dB and 10 dB of attenuation within average $1.27^{\circ}$ between 1.2GHz and 1.9GHz. The input and output return losses between 1.4 GHz and 1.9 GHz are less than 10 dB over the attenuation range of 0 dB and 10 dB.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.3
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• pp.74-78
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• 2011

In this paper, the bandpass filter for ITS system of 5.8 GHz is proposed by using the dual-mode resonator with the radial stub. As alternating the open stub with the radial stub, the size of the dual mode resonator can be reduced about 39.6% and the out-of-band characteristics of the bandpass filter using dual mode resonator can be enhanced from 19.4 dB to 29.1 dB by using the stub of $6.9{\Omega}$ i.e. realized by parallel two radial stubs with $60^{\circ}$ angle. The fabricated bnadpass filter using the dual mode resonator has the center frequency of 5.72 GHz with the fractional bandwidth of 4.1%. Also, the filter has the insertion loss and return loss of 1.79 dB and 19.4 dB, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.141-147
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• 2008

This paper describes the design of frequency down converting Mixer in the receiver to use compound semiconductor and CMOS product process. The basic theory and structure of frequency down converting Mixer is surveyed, and we design mixer circuit with active balun which use the compound semiconductor and CMOS process. This mixer convert a single ended signal to differential signal at input port of RF and LO instead of matching circuit to get dual band balanced mixer structure and characteristic broadband. This designed mixer has a conversion gain $-1{\sim}-6[dB]$ at $2{\sim}6[GHz]$ bandwidths. However, the simulation of the designed mixer with active balun has the result of a 7[dB] conversion gain for -2[dBm] LO input power and -10[dBm] input P1[dB] at 5.8[GHz].

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.900-905
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• 2006

In this paper, PIFA antenna for $2.40{\sim}2.482GHz\;and\;5.75{\sim}5.85GHz$ is designed, fabricated, and measured. The prototype consist of hair-pin and short-pin. To obtain suitable bandwidth, the form layer is inserted between ground plane and substrate. Important parameters in the design are hair-pin length, width, position, air-gap height, and feed point position. From these parameters optimized, a PIFA antenna is fabricated and measured. The measured results of the antenna are obtained as follows results. The resonant frequency of the fabrication PIFA antenna is 2.37GHz and 5.86GHz bandwidth for approximately 90MHz with 350MHz(VSWR<2.0) and the gain is $1.91{\sim}4.37dBi$. H-plan and E-plan at 2.4GHz and 5.8GHz are shown as $52.83^{\circ},\;85.90^{\circ}\;and\;68.68^{\circ},\;52.143^{\circ}$ respectively.

• Journal of Astronomy and Space Sciences
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• v.25 no.1
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• pp.61-70
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• 2008

As the second step of the real time monitoring system of the solar radio disturbance, we constructed a 2.8 GHz radio receiver with 500 MHz bandwith. Using the control and observing system (Yoon et al. 2004), we observed the Sun, and found some frequencies, which disturb the Solar radio flux to be observed. DMB and aiport control frequencies are identified as responsible for this disturbance. As well as the testing the receiver, the measurment of the radio environment at 2.8 GHz with 500 MHz bandwith are carried out around Chungbuk National University. In fact, the radio power of the two frequencies, 2.649 GHz and 2.874 GHz is so high that we can not observe the Solar radio signal at 2.8 GHz. We report some results of this measurment and suggest the method to overcome this problem. We conclude also that the frequecies, which are important for the astronomy, should be protected in the future.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.1014-1020
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• 2009

In this paper, a novel UWB(Ultra Wide-band) antenna with suppressed band of IEEE 802.11a($5.15{\sim}5.825\;GHz$) WLAN was designed and fabricated by using SRR(Split Ring Resonator) with band rejection property. MWS(Micro-wave Studio) of CST company was utilized in the design stage. The antenna was fabricated on a substrate, Rogers 4003, with the thickness of 0.8 mm and relative permittivity of 3.38. The measured result shows that the proposed antenna has a good return loss below -10 dB and group delay below 1nsec over UWB communication band($3.1{\sim}10.6\;GHz$) except WLAN band. It also shows the omni-directional radiation pattern.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.9
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• pp.749-755
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• 2017

In this paper, a wideband microwave absorber for X-band(8~12 GHz) applications is proposed. The structure of the proposed absorber unit cell consists of a resonator with a slot and slit, a backing ground plate, and a Taconic RF-30(${\varepsilon}_r=3$, $tan{\delta}=0.0014$) substrate with a dimension of $8.5{\times}8.5{\times}0.5mm^3$. The proposed absorber has a dual resonance at 9.83 and 10.37 GHz. To demonstrate the operating principle of the proposed absorber structure at each resonance frequency, the simulated current distributions on the unit cell are analyzed. To verify the performance of the proposed absorber, a prototype absorber was fabricated with a planar array of $20{\times}20$ unit cells. The measured results exhibit two absorptivity peaks stronger than 99 % and full-width at half-maximum(FWHM) bandwidth of 1.1 GHz(9.51~10.61 GHz).