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95 results on '"Asano, Kazunori"'

8. Improvement of intermodulation distortion asymmetry characteristics with wideband microwave signals in high power amplifiers

Author

Takenaka, Isao, Ishikura, Kohji, Takahashi, Hidemasa, Hasegawa, Kouichi, Asano, Kazunori, and Iwata, Naotaka

Subjects
CDMA technology -- Research, Power amplifiers -- Design and construction, Baseband -- Research, Field-effect transistors -- Design and construction, Electric distortion -- Control, Code Division Multiple Access technology, Business, Computers, Electronics, Electronics and electrical industries
Abstract

This paper presents the improvement techniques of intermodulation-distortion asymmetries with wide carrier-spacing signals in L/S-band high power amplifiers. We proposed a novel circuit technique to directly connect LC series resonant circuits to the gate and drain electrodes of the transistor die in a package for baseband terminations with a wide frequency range. By applying this circuit technique to a 28-V operation 200-W GaAs heterojunction field-effect transistor (HJFET) amplifier, the third-order intermodulation distortion (IMD3) asymmetries were improved even if the two-tone carrier spacing ([DELTA]f) exceeds 100 MHz. In addition, we analyzed the IMD3 asymmetries of a Doherty amplifier through the IMD3 vector combination of the main and peak amplifiers. A newly developed 28-V operation 200-W GaAs HJFET Doherty amplifier with source and load baseband terminations also delivered flat IMD3 characteristics against the [DELTA]f over 50 MHz. Index Terms--Baseband, difference frequency, Doherty amplifier, heterojunction field-effect transistors (HFETs), high power, intermodulation distortion (IMD) asymmetry, wideband code division multiple access (W-CDMA).

Published
2008

9. A distortion-cancelled doherty high-power amplifier using 28-V GaAs heterojunction FETs for W-CDMA base stations

Author

Takenaka, Isao, Ishikura, Kohji, Takahashi, Hidemasa, Hasegawa, Kouichi, Ueda, Takashi, Kurihara, Toshimichi, Asano, Kazunori, and Iwata, Naotaka

Subjects
CDMA technology -- Research, Electric distortion -- Research, Field-effect transistors -- Research, Code Division Multiple Access technology, Business, Computers, Electronics, Electronics and electrical industries
Abstract

An L/S-band 330-W distortion-cancelled Doherty GaAs field-effect transistor (FET) amplifier has been successfully developed optimizing the main and peak amplifiers load impedance shift. The amplifier employed a pair of 28-V operation 150-W GaAs heterojunction FETs. It demonstrated low third-order intermodulation of -37 dBc with a drain efficiency of 42% at an output power of 49 dBm around 6-dB backoff level under the two-carrier wideband code-division multiple-access (W-CDMA) signals of 2.135 and 2.145 GHz. To our knowledge, these represent the best results ever reported among the simple high-power FET amplifiers for W-CDMA base stations. In addition, we proposed the evaluation techniques to obtain each AM--AM and AM--PM characteristics of the main and peak amplifiers in an operating Doherty amplifier, and have experimentally proven the distortion cancellation effect in the GaAs FET Doherty amplifier. Index Terms--Distortion cancellation, Doherty amplifier, efficiency, heterojunction field-effect transistors (HFETs), high power, wideband code division multiple access (W-CDMA).

Published
2006

32. Thermal conductivity and mechanical properties of pitch-based carbon fibre reinforced aluminium composites fabricated by squeeze casting.

Author

Asano, Kazunori

Subjects
*THERMAL conductivity, *MECHANICAL properties of metals, *CARBON fibers, *METAL castings, *SQUEEZE casting
Abstract

Pure aluminium and high-silicon aluminium alloy were reinforced with the discontinuous pitchbased carbon fibres by squeeze casting, then the thermal conductivity and the mechanical properties of the composites were investigated. Optical microscopy revealed that the fibres were in a random planar arrangement, and the transmission electron microscopy revealed that there is no interfacial reaction between the matrices and the fibres. The random planar arrangement of the fibres leads to the anisotropy of the composite. The fibre-reinforcement increased the thermal conductivity in the parallel direction for both pure aluminium and its alloy matrices, while the thermal conductivity decreased in the vertical direction. The increase in the elastic modulus by the reinforcement was not observed for both matrices. The proof stress of the pure aluminium increased by the reinforcement especially in the parallel direction, while that of the high-silicon alloy decreased by the reinforcement. [ABSTRACT FROM AUTHOR]

Published
2018
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50. Wear Behavior of In Situ Mg2Si Particle-Dispersed Magnesium Alloys

Author

Asano, Kazunori

Abstract

Magnesium alloys, in which the in-situ Mg2Si particles were dispersed, were fabricated by a casting process, and the dry sliding wear behavior of the alloys was investigated. Optical microscopy revealed that the polygonal Mg2Si particles were homogeneously dispersed in the alloys. Mg2Si particle volume fractions in the alloys were 7 and 11 vol%. Although the wear loss of the alloy decreased due to the particle-dispersion, there was no difference in the wear loss between the alloys with different volume fractions. The worn surfaces of the particle-dispersed alloys were covered with the crumbled Mg2Si particles, which would prevent seizure between the alloy and the steel counterpart, leading to an improvement in the wear resistance of the alloy. The particle-dispersion slightly decreased the scatter of the coefficient of friction during the wear for the low sliding speed and load, but the effect of the dispersion was not clearly observed for the high speed and load.

Published
2017
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