Browsing by Author "Kuo, Fang-Yao"

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An Invisibility Cloak Design at Microwave Frequency Using Commonly Used Materials
(2014)
Hwang, Ruey-Bing (Raybeam)
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Kuo, Fang-Yao
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資訊工程學系
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電機學院
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Department of Computer Science
In this work, we present a novel cloaking structure designed at microwave frequency. Different from the cloaking structures in need of effectively negative refractive index medium, such a structure is composed of a regular dielectric medium and metallic cylinders array. From the numerical simulation, we may observe that the cloaking outside a metallic cylinder can mold the propagation of energy flow, reducing the backward scattering of the incident wave.
High-Isolation X-Band Marine Radar Antenna Design
(2014-05-01)
Kuo, Fang-Yao
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Hwang, Ruey-Bing
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電機工程學系
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Department of Electrical and Computer Engineering
This paper presents a high-isolation printed antenna array for marine radar applications. The antenna array is composed of 32 identical square microstrip patches operated at a center frequency of 9.35 GHz and includes a 100-MHz bandwidth (subject to a 1.5:1 voltage standing wave ratio [VSWR]). The patch antennas are arranged in four arms, each of which contains eight elements and is series-fed using Chebyshev tapering (25 dB side-lobe level). To apply the antenna in marine radar applications, an antenna with horizontal polarization was employed because, in comparison with vertical polarization, it can relatively reduce the sea clutter reflectivity. Therefore, a slit was carved on each patch element to change the current path, thereby enabling horizontal polarization. The antenna gain, 3-dB beamwidth, side-lobe level, and front-to-back ratio were 22 dBi, 5.3 degrees, 26.4 dB, and 38.5 dB, respectively. Additionally, metallic baffles were introduced for increasing the isolation between the transmitting and receiving antennas to 60 dB.
Improvement on the noise performance of InAs-based HEMTs with gate sinking technology
(2010-11-01)
Hsu, Heng-Tung
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Kuo, Chien-I
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Chang, Edward Y.
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Kuo, Fang-Yao
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材料科學與工程學系
Improvement on the RF and noise performance for 80 nm InAs/In(0.7)Ga(0.3)As high-electron mobility transistor (HEMT) through gate sinking technology is presented. After gate sinking at 250 degrees C for 3 min, the device exhibited a high transconductance of 1900 mS/mm at a drain bias of 0.5 V with 1066 mA/mm drain-source saturation current. A current-gain cutoff frequency (f(T)) of 113 GHz and a maximum oscillation frequency (f(max)) of 110 GHz were achieved at extremely low drain bias of 0.1 V. The 0.08 x 40 mu m(2) device with gate sinking demonstrated 0.82 dB minimum noise figure and 14 dB associated gain at 17 GHz with only 1.14 mW DC power consumption. Significant improvement in RF and noise performance was mainly attributed to the reduction of gate-to-channel distance together with the parasitic source resistance through gate sinking technology. (C) 2010 Elsevier B.V. All rights reserved.
Linearity Characteristics of Field-Plated AlGaN/GaN High Electron Mobility Transistors for Microwave Applications
(2010)
Huang, Jui-Chien
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Hsu, Heng-Tung
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Chang, Edward-Yi
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Lu, Chung-Yu
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Chang, Chia-Ta
A field-plated (FP) AlGaN/GaN high electron mobility transistor (HEMT) was fabricated. Investigations on the linearity characteristics were performed through two-tone and wide band code division multiple access (WCDMA) modulated excitations. The FP-HEMT exhibited an improved breakdown voltage of 160 V compared with that of the conventional HEMT. Additionally, a higher output power of 25.4 dBm with 43% power added efficiency at a 30 V drain bias at 2 GHz was achieved. When biased at 30 V and 15 mA/mm current density, the third-order intermodulation (IM3) level was measured to be -27.1 dBc (at P(1dB)) and the adjacent channel power rejection (ACPR) was -33.8 dBc (at P(1dB)) under WCDMA modulation at 2 GHz. Measurement results revealed that the field-plated structure improved the linearity performance over the conventional structure at high output power levels even beyond P(1dB). (C) 2010 The Japan Society of Applied Physics