• Journal of IKEEE
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• v.24 no.4
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• pp.1093-1097
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• 2020

This work describes the design and characterization of a Ku-band monolithic microwave integrated circuit (MMIC) power amplifier (PA) for satellite communication applications. The device technology used relies on 0.25 ㎛ gate length gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (PHEMT) of wireless information networking (WIN) semiconductor foundry. The developed Ku-band PHEMT MMIC power amplifier has a small-signal gain of 22.2~23.1 dB and saturated output power of 34.8~35.4 dBm over the entire band of 13.75 to 14.5 GHz. Maximum saturated output power is a 35.4 dBm (3.47 W) at 13.75 GHz. Its power added efficiency (PAE) is 30.6~37.83% and the chip dimensions are 4.4 mm×1.9 mm. The developed 3 W PHEMT MMIC power amplifier is expected to be applied in a variety of Ku-band satellite communication applications.

• Korean Journal of Remote Sensing
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• v.27 no.5
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• pp.543-553
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• 2011

Sea ice concentration calculated from the AMSR-E onboard Aqua satellite by using NASA Team2 sea ice algorithm has proven to be very accurate over sea ice in Antarctic Ocean. When glacial ice such as icebergs and ice shelves are dominant in an AMSR-E footprint, the accuracy of the ice concentration calculated from NASA Team2 algorithm is not well maintained due to the different microwave characteristics of the glacial ice from sea ice. We extracted the concentrations of sea ice and glacial ice from two ENVISAT ASAR images of George V coast in southern Antarctica, and compared them with NASA Team2 sea ice concentration. The result showed that the NASA Team2 algorithm underestimates the concentration of glacial ice. To interpret the large deviation of estimation over glacial ice, we analyzed the characteristics of microwave radiation of the glacial ice in PR(polarization ratio), GR(spectral gradient ratio), $PR_R$(rotated PR), and ${\Delta}GR$ domain. We found that glacial ice occupies a unique region in the PR, GR, $PR_R$, and ${\Delta}GR$ domain different from other types of ice such as ice type A, B, and C, and open water. This implies that glacial ice can be added as a new category of ice to the AMSR-E NASA Team2 sea ice algorithm.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.701-706
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• 2008

High frequency dielectric ceramics have potential for applications in mobile and satellite communications systems at frequencies higher than 10GHz. The Ba$(Zn_{1/3}Ta_{2/3})O_3$ ceramics are known to have a high quality factor, a small temperature coefficient of the resonance frequency and a high dielectric constant. On the other hands, sintering at high temperature for extended time is required to obtain the ordered structure for high quality factor. In this study, the microwave dielectric properties of $ZrO_2$ and NiO-added Ba$(Zn_{1/3}Ta_{2/3})O_3$ ceramics prepared by solid-state reaction have been investigated. Adding $ZrO_2$ and NiO could effectively promote the densification even the case of decreasing the sintering time. At the surface of samples, secondary phase of Ba-Ta compounds was formed possibly due to the evaporation of ZnO, however, the interior of the samples remained as pure Ba$(Zn_{1/3}Ta_{2/3})O_3$. The samples sintered at $1600^{\circ}C$ for 2h exhibited 1:2 ordering of Zn and Ta cations. Excellent microwave dielectric properties of $Q{\cdot}f$(>96,000 GHz) and ${\varepsilon}_r$=30 has been obtained.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2184-2189
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• 2009

China is one of the countries in which flood occurs most frequently in the world and with the current economic growth; flood disaster causes more and more economic losses. Chinese government pays more attention to flood monitoring and assessment by space technology. Since1983, NOAA(AVHRR), Landsat-TM, LANDSAT-ETM+, JERS-1, SPOT, ERS-2, Radarsat-1, CBERS-1, Envisat have been used for flood monitoring and assessment. Due to the bad weather conditions during flood, microwave remote sensing is the major tools for flood monitoring. Envisat is one of the best satellite with powerful SAR. Its application for flood monitoring has been studied and its near real time(NRT) application can be realized on the basis of real-time delivery of image. During the 2005, 2006 and 2007 flood seasons, over the 31 NRT flood monitoring based on Envisat, had been carried out in Yangtze, Songua, Huaihe, pearl river basin. The result shows that Envisat SAR is very useful data source for flood disaster monitoring and assessment.

• Journal of the Korean Professional Engineers Association
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• v.41 no.5
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• pp.55-58
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• 2008

GPS is the global Navigation Satellite System which is developed by the United States Department of Defense as an abbreviation of the Global Positioning System. The GPS uses a constellation of 24 Medium Earth Orbit satellites that transmit precise microwave signals, that enable GPS receivers to determine their location, speed, direction, and time. Following, the shooting down of Korean Air Lines Flight 007 in 1983. President Ronald Reagan issued a directive making the system available free for civilian use as a common good. Since then, GPS has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying, commerce, scientific uses, and hobbies such as geocaching. GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1564-1568
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• 1987

A design methodology for front ends of a Direct Broadcasting satellite (DBS) Receiver for X-band was reported by utilizing Monolithic Microwave Integrated Circuits (MMIC) technology. The frequency converter including a three-stage low-noise amplifier, a image frequency rejection filter, and a mixer and buffer amplifier was designed by a Home-made CAD program. The results of computer simulation using the CAD program showed that overall gain was over 36.63dB, and noise figure below 2.55dB, respectively.

• Proceedings of the KSRS Conference
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• v.2
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• pp.993-996
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• 2006

NOAA operational bulk SST product (Reynolds et al, 2002) is very popular global SST data sets and is extensively used for various studies. However, the original time resolution is weekly and relatively large. On the other hand, there exist many new global SST data sets at present. In this study, we compare many global SST data sets including NOAA operational bulk SST product, CAOS OI SST product, Microwave Optimum Interpolation (MWOI) SST, Real Time Global (RTG) SST and JMA merged satellite and in situ Global Daily (MGD) SST.

• ETRI Journal
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• v.26 no.4
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• pp.307-314
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• 2004

The application of a discrete pseudomorphic high electron mobility transistor (p-HEMT) as a grounded switch allows for the development of low cost phase shifters and phase modulators operating in a Ku band. This fills the gap in the development of phase control devices comprising p-i-n diodes and microwave monolithic integrated circuits (MMICs). This paper describes a discrete p-HEMT characterization and modeling in switching mode as well as the development of a low-cost four-bit phase shifter and direct quadrature phase shift keying (QPSK) modulator. The developed devices operate in a Ku band with parameters comparable to commercially available MMIC counterparts. Both of them are CMOS compatible and have no power consumption. The parameters of the QPSK modulator are very close to the requirements of available standards for satellite earth stations.

• Progress in Superconductivity and Cryogenics
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• v.7 no.1
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• pp.13-16
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• 2005

High temperature superconductor, $\YBa_2Cu_3O_{7-x}$ (YBCO) and ferroelectric, $\Ba_{0.1}Sr_{0.9}TiO_{3}$ (BST) multilayer thin films were deposited using on MgO(100) substrates pulsed laser deposition. The thin films exhibited only (001) peaks of YBCO and 1357 The HTS thin films demonstrated excellent zero resistance temperature of 92.5 K. We designed and fabricated HTS ferroelectric phase shifter using high frequency system simulator and standard photolithography method, respectively The HTS phase shifter shows a low insertion loss (2.97 dB) and large phase change ($\162^{circ}$) with 40 V do bias at 10 GHz. The HTS phase shifter shows 54 of figure of merit. These results can be applicable to phased anay antenna system for satellite communication services.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.11
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• pp.58-65
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• 1993

The Ku-band GaAs MESFET mixer is designed and implemented using the LINMIC+, the microwave CAD simulator. The RF and IF is 14.0GHz and 1.0GHz, respectively. P$_{LO}$ is 0dBm, it can be obtained 5.8dB of the minimum noise figure at 1.4GHz and 5.8dB of the maximum conversion gain at 1.45GHz. Effects of bias and power level of local oscillator frequency are observed and the characteristics are verified.