• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1666-1671
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• 2022

The structure of a high-power gain-flattened long wavelength band (L-band) optical amplifier was optimized, which was implemented for 64-channel wavelength division multiplexed optical signals with a channel spacing of 50 GHz. The output characteristics of this L-band amplifier were measured and analyzed. The amplifier of the optimized two-stage amplification configuration had a flattened gain of 20 dB within 1 dB deviation between 1570 and 1600 nm for -2 dBm input power condition. The noise figure under this condition was minimized to within 6 dB in the amplification bandwidth. The gain flattening was realized by considering only the characteristics of gain medium in the amplifier without using additional optical or electrical devices. The proposed amplifier consisted of two stages of amplification stages, each of which was based on the erbium-doped fiber amplifier (EDFA) structure. The erbium-doped fiber length and pumping structures in each stage of the amplifier were optimized through experiments.

• Journal of IKEEE
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• v.26 no.4
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• pp.722-727
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• 2022

In this paper, we present the design and characterization of a power amplifier (PA) monolithic microwave integrated circuit (MMIC) in the X-band. The device is designed using a 0.25 ㎛ gate length AlGaN/GaN high electron mobility transistor (HEMT) on SiC process. The developed X-band AlGaN/GaN power amplifier MMIC achieves small signal gain of over 21.6 dB and output power more than 46.11 dBm (40.83 W) in the entire band of 9 GHz to 10 GHz. Its power added efficiency (PAE) is 43.09% ~ 44.47% and the chip dimensions are 3.6 mm × 4.3 mm. The generated output power density is 2.69 W/mm². It seems that the developed AlGaN/GaN power amplifier MMIC could be applicable to various X-band radar systems operating X-band.

• Journal of IKEEE
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• v.26 no.4
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• pp.693-704
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• 2022

5G service uses mid-band (n78) than existing mobile communication frequencies, so it is necessary to improve 5G coverage by utilizing low-band frequencies below 2 GHz. To this end, the application of Dynamic Spectrum Sharing technology of LTE and 5G-NR system using most of the low-band frequencies is required. In this paper, signaling overhead factors for DSS application and RF issues for terminal implementation are derived, and signaling overhead ratios from the respective perspectives of 5G-NR and LTE for the 1.8GHz band (50MHz width) that can utilize wide-bandwidth among low-band frequencies are estimated. Also handset RF issues were analyzed. Based on the analysis results, if DSS technology using low band is applied, it is expected that excellent 5G service quality can be provided due to 5G coverage improvement when LTE traffic quickly migrates to 5G-NR.

• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.510-515
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• 2022

In this paper, a microstrip patch sensor antenna (MPSA) for detecting the concentration of an ethanol-water solution in a microliter volume is proposed. A rectangular slot was added at the radiating edge of the patch to increase the sensitivity to the relative permittivity change. To improve a low input resistance caused by placing an ethanol-water solution, which is a polar liquid with high dielectric constant and high loss tangent, on the patch, a quarter-wave impedance transformer was added between the 50-ohm feedline and the patch, and the MPSA was fabricated on a 0.76 mm-thick RF-35 substrate. A cylindrical container was made of acryl, and 15 microliters of the ethanol-water solution was tested from 0% to 100% of ethanol concentration at 20% intervals. Experiment results show that the resonant frequency increased from 1.947 GHz to 2.509 GHz when the ethanol concentration of the ethanol-water solution was increased from 0% to 100%, demonstrating the performance as a concentration detecting sensor.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.6 s.336
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• pp.67-74
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• 2005

In this paper, high LO-RF isolation W-band MIMIC single-balanced mixer was designed and fabricated using a branch line coupler and a $\lambda$/4 transmission line. The simulation results of the designed 94 GHz balun show return loss of -27.9 dB, coupling of -4.26 dB, and thru of -3.77 dB at 94 GHz, respectively. The isolation and phase difference were 23.5 dB and $180.2^{\circ}$ at 94 GHz. The W-band MIMIC single-balanced mixer was designed using the 0.1 $\mu$m InGaAs/InAlAs/GaAs Metamorphic HEMT diode. The fabricated MHEMT was obtained the cut-off frequency(fT) of 189 GHz and the maximum oscillation frequency(fmax) of 334 GHz. The designed MIMIC single-balanced mixer was fabricated using 0.1 $\mu$m MHEMT MIMIC Process. From the measurement, the conversion loss of the single-balanced mixer was 23.1 dB at an LO power of 10 dBm. Pl dB(1 dB compression point) of input and output were 10 dBm and -13.9 dBm respectively. The LO-RF isolations of single-balanced mixer was obtained 45.5 dB at 94.19 GHz. We obtained in this study a higher LO-RF isolation compared to some other balanced mixers in millimeter-wave frequencies.

• Journal of electromagnetic engineering and science
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• v.18 no.3
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• pp.182-187
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• 2018

A low profile asymmetrical fractal boundary patch antenna based on reactive impedance surface (RIS) and a mushroom unit cell (MUC) is proposed and studied for dual band operation. The sides of the square patch antenna are replaced with asymmetrical half circled fractal curves for circular polarization operation at patch mode band. The fractal patch antenna is loaded with MUC for dual band operation. The antenna radiation characteristics are investigated and illustrated with both simulated and experimental results in detail. The 10-dB return loss bandwidth are 8.48% (3.21-3.49 GHz) and 2.59% (2.30-2.36 GHz) at upper and lower resonance frequencies, respectively. The 3-dB axial ratio bandwidth is 4.26% (3.21-3.35 GHz). A close agreement between simulation data with experimental results is observed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.715-718
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• 2002

This paper investigated that resonant frequencies of microstrip patch antenna were agile when piezoelectric materials were used as the antenna substrates. When the bias is applied on them, thickness of the substrate is varied according. to the piezoelectric phenomenon. The microstrip patch antenna using Quartz substrate was fabricated and designed by Ensemble v 7.0 simulator. We fabricated the microstrip antennas using Quartz(Y-cut) as its substrate. When the operating frequencies of the microstrip antenna were 7.045GHz, 7.773GHz 8.18GHz the frequency shifts versus electric field, Emax=4[kV/cm], were 21MHz, 26MHz and 28MHz, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1733-1740
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• 2001

A monolithic 5 GHz image reject mixer using a 0.5-m GaAs MESFET technology is designed and simulated. The Mixer exhibits a 13.56 dB down-conversion gain, a SSB (Single SideBand) noise figure of 11.91 dB, an input IP3 (third order intercept point) of -3.73 dBm and a PldB (1-dB compression point) of -11.0 dBm. The critical issue in the image reject mixer is the phase accuracy and magnitude balance of the 90 phase shifting network. The proposed image reject mixer realizes a 90 phase shifter on chip. This phase shifting network does not need any phase adjusting to achieve the phase error specification of 3 over a frequency range from 800 MHz to 1GHz. The simulated overall image rejection ratio is better than 50 dB.

• Journal of the Semiconductor & Display Technology
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• v.15 no.4
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• pp.22-26
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• 2016

In this paper, we measured the efficiency of the receiver for 5.8GHz Microwave Smartphone Charging. We have designed and fabricated 1W and 2W power amplifier, respectively. A 1W power amplifier used a TC3531 power device of TRANSCOM Inc. In addition, a 2W power amplifier using the two TC3531 devices was constructed with divider and combiner. We used the Wilkinson divider theory for divider and combiner. The voltage was measured using the 1W and 2W power amplifier and integrated receivers to the distance of 50cm.

• Information and Communications Magazine
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• v.27 no.2
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• pp.20-26
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• 2010

THz 대역의 주파수 범위는 일반적으로 100GHz ~ 10THz 사이로서, 전자파의 투과성과 광파의 직진성을 동시에 가지고 있다. THz 캐리어 주파수는 대기의 수분에 강하게 흡수되어 1THz 이상에서 1 [dB/m] 정도의 대기 전파감쇠가 발생하나 0.1 [dB/m] 정도의 비교적 낮은 주파수 윈도우가 존재하여 이 영역의 주파수 스펙트럼을 이용한 무선통신시스템의 개발이 활발히 진행되고 있다. 최근 RF MMIC의 기술개발 동향을 고려해 볼 때 무선통신시스템 응용을 위한 가장 유력한 THz 주파수 대역은 H-밴드(220 ~ 325GHz)이다. H-밴드에서 가용한 주파수 대역폭은 약 45GHz 이상이며, 이러한 초광대역폭을 이용하여 10Gbps급 이상의 데이터 전송속도를 ASK 또는 BPSK와 같은 간단한 변조방식으로 용이하게 실현할 수 있다. 본고에서는 THz 대역에서 무선통신 응용을 위한 전파특성 및 주파수 대역, 무선링크 특성과 THz 송수신기 기술에 대하여 알아본다.