• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.5
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• pp.251-258
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• 2002

In this paper, the dipole-fed planar array antenna applied Yagi-Uda antenna away theory to microstrip antenna is designed and fabricated at X-band. The design procedure of the dipole-fed planar array antenna with the wide bandwidth is presented to be easily practiced to a wireless communication system. The radiation pattern, return loss and bandwidth of the antenna are improved by the finite differential time domain(FDTD) numerical method. The propriety of analysis of planar dipole antenna is proved from the measured data. From the measured results, the antenna maximum gain is 4.9dBi at center frequency of 10GHz and frequency bandwidth is about 40%. Front-to-back ratio is 16dB, and half-power beam-width of E-plane and H-plane are 117$^{\circ}$and 156$^{\circ}$, respectively. When VSWR of antenna is less than 2, the measured results are agreed well with the theoretical values in the frequency range from 7.4GHz to 11.88GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.11
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• pp.1137-1140
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• 2011

In this paper, the optimal condition for efficient active frequency multipliers is analyzed. This analysis is based on the effects from transistor nonlinear coefficients, harmonic impedances, and output parasitic components. From the analysis, normalized harmonic power is estimated with the clipping condition of a commercial transistor, and the condition for high conversion efficiency is suggested. From the analysis, a class-F frequency tripler was implemented for the output at 2.475 GHz, showing the maximum efficiency of 22.9 % and the maximum conversion gain of 9.5 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.757-765
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• 1999

In this paper, L-Type aperture coupled circular polarization patch antenna for mobile communication(IMT-2000, 1.9375 GHz), which is capable of being mounted in mobile unit, was designed and fabricated. This antenna is expanded to the $2\times2$ circular polarization array antenna for satellite mobile communications which are using the L-band frequency. The results are as followings : Returnloss 18.56 dB, beamwidth $60^{\circ}$, gain 7 dBd, axial ratio 0.9 dB in the case of single element and returnloss 28.43 dB, beamwidth $38^{\circ}$, gain 9.8dBd, axial ratio 1.5 dB in the case of $2\times2$ array, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.43-52
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• 1996

Nonreciprocal twin-toroid ferrite phase shifter is designed, fabricated, and tested. ABCD matrix method is used to design the phase shifter and to compute its optimum dimen- sions. Quarter-wave two-section impedance matching transformers are utilized in order to match the impedance of the empty guide to that of the ferrite-loaded guide. Driving circuit controls the current needed to drive the phase shifter. Measured insertion loss and VSWR characteristics within the operaring band(9.1GHz ~ 9.5GHz) are less than 1.2dB and 1.15, respectively. After temperature compensation technique is appied to the phase shifter, the measured phase error of the phase shifter is less than $\pm4$ between $-10^{\circ}C\;and\;+60^{\circ}C$.

• Current Optics and Photonics
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• v.8 no.1
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• pp.65-71
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• 2024

We present a Yb-doped narrow-linewidth polarization-maintaining all-fiber amplifier that achieves a high mode-instability (MI) threshold, high output power, and 9.7-GHz spectral linewidth. Six wavelength-multiplexed laser diodes are used to pump this amplifier. First, we construct a high-power fiber amplifier based on a master oscillator-power amplifier configuration for experiments. Subsequently, we examine the MI threshold by individually pumping the amplifier with wavelengths of 976, 974, 981, 974, and 981 nm respectively. The experimental results demonstrate that the amplifier exhibits a high MI threshold (>3.5 kW) when pumped with a combination of wavelengths at 974 and 981 nm. Afterward, we inject an optimized phase-modulated seed with a nearly flat-top spectrum into this amplifier. Ultimately, laser output of 3.2 kW and 9.7 GHz are obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.7
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• pp.944-950
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• 1993

Diodes and GaAs have been commonly used in a mixer design until recently. However, diodes are not preferred to use at the front-end of DBS receiver due to the conversion loss large noise. HEMT has larger conversion gain and better noise characteristics comparing with GaAs MESFET. This paper describes the design procedure, structure, and performance of a mixer, utilizaing HEMT designed by OKI Co. . A mixer configuration in which the local oscillator(LO) signal is applied to the gate is used. When the LO power is 0.01 dBm, the conversion gain of 3.7dB is obtained at IF and the 3 dB bandwidth is 400MMz.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.695-698
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• 2003

This paper presents a Si power LDMOSFET for power amplifiers in the 1.8-2.2GHz frequency range for the base station of personal communication systems. To improve the cut-off frequency, the proposed Si power LDMOSFET has small gate to drain capacitance by shielding the electric fields with extended source electrode and forming the field oxide structure in drain region. The proposed Si power LDMOSFET can be used for a power amplifier and it has 32% of power added efficiency and 39.5dBm of output power when the supply voltage is 28V and the operating frequency is 1.9GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.868-882
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• 2009

In this paper, channel model and wireless link performance analysis for the short-range wireless communication system applications in the terahertz frequency which is currently interested in many countries will be described. In order to realize high data rates above 10 Gbps, the more wide bandwidths will be required than the currently available bandwidths of millimeter-wave frequencies, therefore, the carrier frequencies will be pushed to THz range to obtain larger bandwidths. From the THz atmospheric propagation characteristics based on ITU-R P.676-7, the available bandwidths were calculated to be 68, 48 and 45 GHz at the center frequencies of 220, 300 and 350 GHz, respectively. With these larger bandwidths, it was shown from the simulation that higher data rate above 10 Gbps can be achieved using lower order modulation schemes which have spectral efficiency of below 1. The indoor propagation delay spread characteristics were analyzed using a simplified PDP model with respect to building materials. The RMS delay spread was calculated to be 9.23 ns in a room size of $6\;m(L){\times}5\;m(W){\times}2.5\;m(H)$ for the concrete plaster with TE polarization, which is a similar result of below 10 ns from the Ray-Tracing simulation in the reference paper. The indoor wireless link performance analysis results showed that receiver sensitivity was $-56{\sim}-46\;dBm$ over bandwidth of $5{\sim}50\;GHz$ and antenna gain was calculated to be $26.6{\sim}31.6\;dBi$ at link distance of 10m under the BPSK modulation scheme. The maximum achievable data rates were estimated to be 30, 16 and 12 Gbps at the carrier frequencies of 220, 300 and 350 GHz, respectively, under the A WGN and LOS conditions, where it was assumed that the output power of the transmitter is -15 dBm and link distance of 1 m with BER of $10^{-12}$. If the output power of transmitter is increased, the more higher data rate can be achieved than the above results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.926-931
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• 2005

In this paper, the printed-sleeve monopole antenna which has the small size and the broadband characteristics, is presented and its radiation characteristics are investigated. To conform the broadband characteristics of the proposed antenna, the experimental antenna is designed, fabricated, and its radiation characteristics are measured in PCS band (1.75 GHz${\~}$1.87 GHz). It is shown that the designed antenna has the non-directional pattern in the horizontal plane, the directional pattern in the vertical plane, VSWR less than 1.5, and gain in 2.14 dBi${\~}$3.4 dBi. From these results, the proposed antenna is conformed as a broadband antenna which can be used for the mobile communication indoor antenna extensively.

• ETRI Journal
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• v.36 no.1
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• pp.106-115
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• 2014

In this work, the coplanar waveguide is fabricated on a PES (poly[ether sulfone]) substrate for application to a flexible monolithic microwave integrated circuit, and its RF characteristics were thoroughly investigated. The quality factor of the coplanar waveguide on PES is 40.3 at a resonance frequency of 46.7 GHz. A fishbone-type transmission line (FTTL) structure is also fabricated on the PES substrate, and its RF characteristics are investigated. The wavelength of the FTTL on PES is 5.11 mm at 20 GHz, which is 55% of the conventional coplanar waveguide on PES. Using the FTTL, an impedance transformer is fabricated on PES. The size of the impedance transformer is $0.318mm{\times}0.318mm$, which is 69.2% of the size of the transformer fabricated by the conventional coplanar waveguide on PES. The impedance transformer showed return loss values better than -12.9 dB from 5 GHz to 50 GHz and an insertion loss better than -1.13 dB in the same frequency range.