The pressure characteristics inside single loop oscillating heat pipe （OHP） having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed. Distilled water was used as working fluid inside th...The pressure characteristics inside single loop oscillating heat pipe （OHP） having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed. Distilled water was used as working fluid inside the OHP with different filling ratios of 40%, 60% and 80% of total inside volume. Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency. And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60-96 ℃. Piezoresistive absolute pressure sensor （Model-Kistler 4045A5） was used to take data. The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio.展开更多
A two-stage monolithic low noise amplifier is developed for satellite communication applications,using a 0.5μm enhancement PHEMT technology. The on-chip matched amplifier employs lumped elements to reduce the circuit...A two-stage monolithic low noise amplifier is developed for satellite communication applications,using a 0.5μm enhancement PHEMT technology. The on-chip matched amplifier employs lumped elements to reduce the circuit size, and shows a 5012 noise figure less than 0.9dB, gain greater than 26dB, and return loss less than - 10dB in the S-C band range of 3.5 to 4. 3GHz. The noise figure obtained here is the best result ever reported to date of an MMIC LNA with a gain of more than 20dB for the S-C band frequency range. It is attributed to the low noise performance of the enhancement PHEMT transistor and minimized parasitic resistance of the input match network by a common series source inductor and a unique divided resistance at the drain.展开更多
A three-stage MMIC power amplifier operating from 6to 18GHz is fabricated using 0.25μm A1GaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor（PHEMT）.The amplifier isfully monolithic,with all matching,bi...A three-stage MMIC power amplifier operating from 6to 18GHz is fabricated using 0.25μm A1GaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor（PHEMT）.The amplifier isfully monolithic,with all matching,biasing,and DC block circuitry included on the chip.Thepower amplifier has an average power gain of 19dB over 6～18GHz.At operation frequenciesfrom 6 to 18GHz,the output power is above 33.3dBm,and the maximum output power of the MMICis 34.7dBm at 10Ghz.The input return loss is less than-10db and the out-put return is lessthan-6dB over operating frequency.This power amplifier has,to our knowledge,the best powergain flatness reported at C-X-Ku-band applications.展开更多
基金Project(2011-0009022) supported by Basic Science Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education,Science and Technology of Korea
文摘The pressure characteristics inside single loop oscillating heat pipe （OHP） having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed. Distilled water was used as working fluid inside the OHP with different filling ratios of 40%, 60% and 80% of total inside volume. Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency. And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60-96 ℃. Piezoresistive absolute pressure sensor （Model-Kistler 4045A5） was used to take data. The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio.
文摘A two-stage monolithic low noise amplifier is developed for satellite communication applications,using a 0.5μm enhancement PHEMT technology. The on-chip matched amplifier employs lumped elements to reduce the circuit size, and shows a 5012 noise figure less than 0.9dB, gain greater than 26dB, and return loss less than - 10dB in the S-C band range of 3.5 to 4. 3GHz. The noise figure obtained here is the best result ever reported to date of an MMIC LNA with a gain of more than 20dB for the S-C band frequency range. It is attributed to the low noise performance of the enhancement PHEMT transistor and minimized parasitic resistance of the input match network by a common series source inductor and a unique divided resistance at the drain.
文摘A three-stage MMIC power amplifier operating from 6to 18GHz is fabricated using 0.25μm A1GaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor（PHEMT）.The amplifier isfully monolithic,with all matching,biasing,and DC block circuitry included on the chip.Thepower amplifier has an average power gain of 19dB over 6～18GHz.At operation frequenciesfrom 6 to 18GHz,the output power is above 33.3dBm,and the maximum output power of the MMICis 34.7dBm at 10Ghz.The input return loss is less than-10db and the out-put return is lessthan-6dB over operating frequency.This power amplifier has,to our knowledge,the best powergain flatness reported at C-X-Ku-band applications.
