• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1427-1434
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• 2008

Compact quadruple inverted-f antenna(QIFA) with circular polarization for GPS receiver is proposed. Radiation efficiency is decreased when 4-port antenna is smaller. A new matching method is proposed by considering both a return loss at one port and mutual coupling between ports to increase radiation efficiency. Experimental results show that the proposed QIFA has a 3-dB beamwidth of more than 120 degrees and a front-to-back ratio of more than 15 dB. Also, the QIFA has the peak gain of -2.5 dBic and the axial ratio under 0.5 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.214-219
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• 2011

This paper presents a multi-band low noise amplifier(LNA) with switching operation for 2.4, 3.5 and 5.2 GHz bands using CMOS 0.18 um technology. The proposed circuit uses switching transistors to achieve the input and output matching for multi-band. By using the switching transistors, we can adjust the transconductance, gate inductance and gatesource capacitance at input stage and total output capacitance at output stage. The proposed LNA exhibits gain of 14.2, 12 and 11 dB and noise figure(NF) of 3, 2.9 and 2.8 dB for 2.4, 3.5 and 5.2 GHz, respectively.

• Journal of Navigation and Port Research
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• v.27 no.2
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• pp.217-221
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• 2003

In this work, we used a novel RF-CSP to develop a broadband amplifier MMIC, including all the matching and biasing components, for Ku and K band applications. By utilizing an ACF for the RF-CSP, the fabrication process for the packaged amplifier MMIC could be simplified and made cost effective. STO (SrTiO$_3$) capacitors were employed to integrate the DC biasing components on the MMIC. A pre-matching technique was used for the gate input and drain output of the FETs to achieve a broadband design for the amplifier MMIC. The amplifier CSP MMIC exhibited good RF performance (Gain of 12.5$\pm$1.5 dB, return loss less than -6 dB, PldB of 18.5$\pm$1.5 dBm) over a wide frequency range. This work is the first report of a fully integrated CSP amplifier MMIC successfully operating in the Ku/K band.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.3029-3034
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• 2014

The paper describes the scleral diagnostic system implementation for human eyes by using the scleral color code and vessels sign pattern code generations. The system is based on the high performance DSP image signal processor, programmable gain control for preprocessing and RISC SD frames storage. RGB image signals are optimized by PGC, the edge image is detected form the gray image converted. The processing algorithms are executed by scleral color code generation and scleral vessels sign pattern code creation for discriminating and matching. The scleral symptomatic color code is generated by YCbCr values at memory map tolerated and the vessel sign pattern code is created by digitizing the 24 clock and 13 ring zones, overlay matching and tolerances. The experimental results for performance are that the system runs 40ms, and the color and pattern for diagnostic errors are around 20% and 24% on average. The system and technique enable a scleral diagnosis with subdividing the patterns and patient database.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.6
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• pp.619-627
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• 2014

In this paper, we designed a blade antenna for VHF-UHF band(500 MHz~3 GHz) to be used as aircraft antennas. Unlike previously reported researches that use high-dielectric materials and insert rectangular extended grounds, the antenna structure was designed by optimizing the curvature of both a radiator and an extended ground whose shape is varied by changing the exponent of an n-th polynomial. Based on the optimized structure, we measured impedance matching and gain performances to evaluate the antenna in the VHF-UHF band(500 MHz~3 GHz). As a result, we confirmed that the antenna shows matching characteristics of less than -6 dB and has average gains of greater than -5 dBi in the entire VHF-UHF band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.834-841
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• 2018

A power amplifier for subgigahertz short-range wireless communication using $0.18-{\mu}m$ CMOS technology is presented. It is designed as a differential structure to form easily a virtual ground node, to increase output power, and to design a cascode structure to prevent breakdown. The transistor gate width was determined to maximize the output power and power-added efficiency(PAE), and the balun was optimized through electromagnetic simulation to minimize the loss caused by the matching network. This power amplifier had a gain of more than 49.5 dB, a saturation power of 26.7 dBm, a peak PAE of 20.7 % in the frequency range of 860 to 960 MHz, and a chip size of $2.14mm^2$.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.3
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• pp.467-474
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• 2019

In this paper, we studied a method for a broadband stacked patch antenna structure which is widely used for bandwidth improvement. The characteristics according to the distance between the two patches were analyzed and the impedance matching was optimized by connecting parallel open stubs to the main patch feed line. The shunt matching stub is inserted underneath the parasitic patch and so it does not require additional space, which enables the proposed antenna structure to be advantageous in miniaturizing antenna. The effects of the various parameters on the antenna performance are examined, and we introduced the design procedure for the proposed antenna to operate in the frequency range of 2.3~2.7GHz. Experimental results show that the bandwidth of the proposed antenna is about 480MHz with 2.27~2.75GHz bandwidth. And the antenna gain was 5.8dBi at 2.3GHz and 7.8dBi at 2.6GHz within the bandwidth.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.3
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• pp.489-496
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• 2019

In this paper, we design and fabricate an ultra small dual crossed dipole antenna operating at 2.4 GHz frequency. In order to miniaturize the size of the antenna so that it can be applied to a mobile device, a cross dipole is disposed on the upper two layers and a reflection plane, a horizontal matching circuit and a ground plane are arranged on each layer. The circuit was connected by a vertical through-hole. The size of the fabricated antenna is $21.61mm{\times}16.88mm{\times}1.27mm$, the measured reflection coefficient is -31.5 dB, and the bandwidth below -10 dB is 112 MHz. In addition, since the gain of the antenna is -4 dBi, it has the omnidirectional radiation characteristic, so it can be applied to various fields as an antenna for mobile devices.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.4
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• pp.67-72
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• 2022

This study presents the design of power amplifier (PA) in 60 nm GaN/Si HEMT technology. A customized transistor model enables the designing circuits operating at W-band. The all matching network of the PA was composed of equivalent transformer circuit to reduce matching loss. And then, equivalent transformer is several advantages without any additional inductive devices so that a wideband power characteristic can be achieved. The designed die area is 3900 ㎛ × 2300 ㎛. The designed results at center frequency achieved the small signal gain of 15.9 dB, the saturated output power (Psat) of 29.9 dBm, and the power added efficiency (PAE) of 24.2% at the supply voltage of 12 V.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.430-439
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• 2007

In this paper, we propose a broadband TEM horn antenna optimized using a genetic algorithm. The characteristics required for the TEM horn are the broad matching bandwidth from 2 GHz to 10 GHz and high gain in broadside with a small gain deviation within that bandwidth. In addition, a broadband balun is designed to improve the portability and to reduce the total size of the antenna. The measured return loss of the proposed TEM horn with the broadband balun is less than -10 dB(VSWR<2) from 2 GHz to 10 GHz. Compared to a conventional triangular type TEM horn, the proposed antenna shows about 80 % reduced volume and gives the broadside gain about 12 dBi with a gain deviation less than 6 dB from 2 GHz to 10 GHz. The time domain measurement shows less than 0.4 ns group delay and the pulse measurement using the transmitting signal with the rising time of 58.5 ps shows the received pulse with the rising time of 66.5 ps, which is less than 10 % rising time variation.