• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.57-58
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• 2018

In this paper, we studied a design method for a quasi-Yagi antenna operating over a broad bandwidth covering the UHF RFID(902-928 MHz) and GNSS(1,164-1.605 MHz). The proposed antenna is composed of three elements(dipole, reflector, and director) and fed by a coplanar waveguide. To reduce its size, a balun is integrated inside the antenna, and the ends of both the dipole and reflector are bent. Broadband impedance matching was obtained by placing the director near to the dipole and loading a chip capacitor inside the antenna. The antenna, designed through simulations, was fabricated on an FR4 substrate with 0.8 mm thickness. The experiment results for the antenna characteristics agree very well with the simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.89-96
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• 2000

In this paper, the design theory of the corrugated polarizer using square waveguide is proposed. In order to analysis the characteristic of square waveguide discontinuity as well as achievement of the low VSWR, we apply the modified $TE^\chi_mn$ mode matching method and the corrugated exponential function to the polarizer design. The results show a broadband characteristic that phase shift angle is nearly appeared $90^{\circ}$ in the range of 11.7-15.8GHz. Especially, we could be designed the Ku-band dual polarizer for the satellite broadcasting transponder with 300MHz bandwidth. Its phase shift angle and maximum VSWR, axial ratio are $90^{\circ},\pm1^{\circ}$, 1.03, and 1.0001 in the range of 11.7-12.0GHz and 14.5-14.8GHz, respectively.

• ETRI Journal
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• v.41 no.2
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• pp.167-175
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• 2019

A wideband dual-polarized antenna coupling cross resonator is proposed for LTE700/GSM850/GSM900 base stations. An additional resonance is introduced to obtain strong coupling between the dipole and resonator. Moreover, the input impedance of the proposed antenna is steadily close to $50{\Omega}$, which results in better impedance matching. Therefore, a wide bandwidth can be achieved with multiresonance. A prototype is fabricated to verify the proposed design. The measured results show that the antenna has a fractional bandwidth of 35.7% from 690 MHz to 990 MHz for ${\mid}S_{11}{\mid}$ < -15 dB. Stable radiation patterns as well as gain are also obtained over the entire operating band. Moreover, a five-element antenna array with an electrical downtilt of $0^{\circ}$to $14^{\circ}$ is developed for modern base station applications. Measurement shows that a wide impedance bandwidth of 34.7% (690 MHz to 980 MHz), stable HPBW (3-dB beamwidth) of $65{\pm}5^{\circ}$, and high gain of $13.8{\pm}0.6dBi$ are achieved with electrical downtilts of $0^{\circ}$, $7^{\circ}$, and $14^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.7
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• pp.608-616
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• 2009

This paper presents a broadband CPS-fed Yagi-Uda antenna. The antenna has a feedline structure much simpler than other Yagi-Uda antennas and it provides more design flexibility in arranging the reflector. To improve the impedance matching, a tapered CPS line is inserted between the thick and thin feedlines. The proposed antenna exhibits the bandwidth of $3.9{\sim}5.9$ GHz (|G| < -10 dB) and the gain of $6.5{\sim}8$ dBi within that bandwidth. At the center frequency of 4.9 GHz, the antenna shows the gain of 7.4 dBi, and HPBW of $98^{\circ}$ along the x-z plane and $73^{\circ}$ along the x-y plane.

• Journal of Advanced Navigation Technology
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• v.9 no.2
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• pp.103-109
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• 2005

This paper presents the design of a broadband hybrid mixer using dual-gate FET topology with a low-pass filter which improves return loss of output to isolate RF and LO signal. The low-pass filter shows the isolation with RF and LO signal of better than 40 dBc from 1.5 GHz to 5.5 GHz. The dual-gate mixer which has been designed by using cascade topology operates when the lower FET is biased in linear region and the upper FET is in saturation region. The input matching circuit has been designed to have conversion gain from 1.5 GHz to 5.5 GHz. The designed mixer with low-pass filter shows the conversion gain of better than 7 dB from 1.5 GHz to 5.5 GHz at the low LO power level of 0 dBm with the fixed IF frequency of 21.4 MHz.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.583-585
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• 2012

In this paper, we introduce a design method for a broadband planar quasi-Yagi antenna (QYA) for terrestrial digital television (DTV) receiving. The coplanar strip line feeding the driver dipole is connected to a microstrip line and is terminated by short circuit. By appending a wide strip-type director at a location close to the driver dipole, a broadband impedance matching and a gain characteristics in a high frequency region are obtained. The gain characteristics in a low frequency region are improved by adding a reflector formed by a truncated ground plane. To reduce the antenna size, the strip-type dipole and reflector are modified to half bowtie (V)-shaped elements. The effects of various parameters on the antenna characteristics are examined. An antenna, as an design example for the proposed antenna, is designed for the operation in the frequency band of 470-806 MHz for terrestrial DTV. The optimized antenna is fabricated on an FR4 substrate and tested experimentally to verify the results of this study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4165-4170
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• 2012

In this paper, a method for the improvement in the gain and bandwidth of a microstrip-fed broadband planar quasi-Yagi antenna (QYA) is studied. The broadband characteristics of the QYA are achieved from the coplanar strip-fed planar dipole driver and a parasitic director close to the driver. In order to obtain stable gain variation over the required frequency band, a director and a ground reflector are appended to the driver having a nearby parasitic director. The QYA is fed through an integrated balun composed of a microstrip line and a slot line which are terminated in a short circuit. By adjusting the feeding point, a broadband impedance matching is obtained. A QYA with an operating frequency band of 1.75-2.7 GHz and a gain > 4.5 dBi is designed and fabricated on an FR4 substrate with dielectric constant of 4.4 and thickness of 1.6mm. The experimental results show that the fabricated antenna has good performance such as a broad bandwidth of 59.7%(1.55-2.87 GHz), a stable gain between 4.7-6.5 dBi, and a front-to-back ratio > 10 dB. The measured data agree well with the simulation, which validates this study.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.694-700
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• 2009

In this paper, we propose a RFID tag antenna with low performance degradation due to nearby dielectric materials. The proposed antenna is designed to be appropriate for ink printing fabrication. The antenna is designed to operate in UHF band of $860{\sim}960$ MHz. The antenna uses a T-matching network in the middle of the main body and two parasitic patches in vicinity for complex conjugate matching with a commercial tag chip. In addition, the two parasitic patches induce currents at different dielectric constants of nearby dielectric materials. This can minimize the performance degradation due to nearby dielectric materials. The measured results show the half power matching bandwidth from 844 MHT to 1,268 MHz. It exhibits the reading distance of about 3.5 m in free space when the tag antenna is used with the commercial reader antenna (transmitting power of 20 dBm and the reader antenna gain of 6 dBi). When the tag is attached on dielectric materials of wood and FR4, the resulting reading distances are 2.61 m and 2.51 m, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.8
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• pp.788-793
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• 2004

This paper proposes new configuration for the dual power amplifier that operates at 5.8 GHz for the wireless LAN and 1.8 GHz for the PCS. It dose not select the input signal but amplify the dual band signals simultaneously. Broadband diplexer is used at the input to separate the dual band signals. Output power of each amplifier is 1 W. The PBG is employed to improve the performance of power amplifier. Generally, the PBG is employed at the end of output matching network. But in this paper, the PBG is employed in the load pull output matching circuit of amplifer to maximize the output power.

• International Journal of Contents
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• v.2 no.1
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• pp.29-33
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• 2006

The common-source low noise amplifier(LNA) with inductive degeneration using a genetic algorithm is designed and tested for a down converter in an industrial, scientific and medical (ISM) band application and a wireless broadband internet service (WiBro). The genetic algorithm optimizes the reflection coefficients to be well matched the input and output ports between multistage transistor amplifiers, and it generates low voltage standing wave ratio as well as gain flatness of the amplifier. The stability and the gain flatness of the LNA have been improved by combining the matching circuits and the series feedback microstrip lines with inductive degeneration at common-source port. In the frequency range of ISM band and WiBro application operating at $2.3GHz{\sim}2.5GHz$, the measured power gain and maximum voltage standing wave ratio (VSWR) of the LNA are $41{\pm}0.5dB$ and 1.3, and the noise figure of the LNA is lower than 0.85dB. The above results are agreed well with the theoretical values of the amplifiers.