We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer(HEB)mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-...We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer(HEB)mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-meter Dome A Terahertz Explorer(DATE5)telescope.By evaluating the double sideband(DSB)receiver noise temperature(Trec)across a wide frequency range from 0.2 THz to 1.34 THz and with a large number of bias points,a broad optimal bias region has been observed,illustrating a good bias applicability for multipixel application since the performance of the HEB mixer is uniquely determined by each bias point.The noise temperature of the HEB mixer has been analyzed by calibrating the noise contribution of all RF components,whose transmissions have been measured by a time-domain spectroscopy.The corrected noise temperature distribution shows a frequency independence relation.The dependence of the optimal bias region on the bath temperature of the HEB mixer has also been investigated,the bath temperature has limited effect on the lowest receiver noise temperature until 7 K,however the optimal bias region deteriorates obviously with increasing bath temperature.展开更多
Flicker noise and deep level transient spectroscopy were used to characterize defect properties of GaN films with different buffer structures. Results indicate improved properties with the use of intermediate temperat...Flicker noise and deep level transient spectroscopy were used to characterize defect properties of GaN films with different buffer structures. Results indicate improved properties with the use of intermediate temperature buffer layers due to the relaxation of residue strain in the films.展开更多
A mathematical model for insertion loss in a micro-perforated muffler with the effects of temperature gradient, gas flow speed and structure parameter is obtained by the mode matching technique. By dividing the microp...A mathematical model for insertion loss in a micro-perforated muffler with the effects of temperature gradient, gas flow speed and structure parameter is obtained by the mode matching technique. By dividing the microperforated tube into N segments, and assuming the flow speed and temperature are constant in each element, sound pressure and volume velocity of each segment can be readily acquired. The transmission matrix of microperforated muffler can be established based on the continuity condition of adjacent elements on the boundary. The numerical results of the present theory are calculated and the experiment is performed in Shanghai-495A engine. The experimental results of microperforated muffler show that they are in good agreement with the theoretical results.展开更多
基金Project supported by the Chinese Academy of Sciences(Grant Nos.GJJSTD20180003 and QYZDJ-SSW-SLH043)the National Key Basic Research and Development Program of China(Grant Nos.2017YFA0304003 and 2018YFA0404701)+1 种基金the National Natural Science Foundation of China(Grant Nos.11603081,11673073,U1831202,and 11873099)PICS projects between the CAS and the CNRS.
文摘We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer(HEB)mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-meter Dome A Terahertz Explorer(DATE5)telescope.By evaluating the double sideband(DSB)receiver noise temperature(Trec)across a wide frequency range from 0.2 THz to 1.34 THz and with a large number of bias points,a broad optimal bias region has been observed,illustrating a good bias applicability for multipixel application since the performance of the HEB mixer is uniquely determined by each bias point.The noise temperature of the HEB mixer has been analyzed by calibrating the noise contribution of all RF components,whose transmissions have been measured by a time-domain spectroscopy.The corrected noise temperature distribution shows a frequency independence relation.The dependence of the optimal bias region on the bath temperature of the HEB mixer has also been investigated,the bath temperature has limited effect on the lowest receiver noise temperature until 7 K,however the optimal bias region deteriorates obviously with increasing bath temperature.
文摘Flicker noise and deep level transient spectroscopy were used to characterize defect properties of GaN films with different buffer structures. Results indicate improved properties with the use of intermediate temperature buffer layers due to the relaxation of residue strain in the films.
文摘A mathematical model for insertion loss in a micro-perforated muffler with the effects of temperature gradient, gas flow speed and structure parameter is obtained by the mode matching technique. By dividing the microperforated tube into N segments, and assuming the flow speed and temperature are constant in each element, sound pressure and volume velocity of each segment can be readily acquired. The transmission matrix of microperforated muffler can be established based on the continuity condition of adjacent elements on the boundary. The numerical results of the present theory are calculated and the experiment is performed in Shanghai-495A engine. The experimental results of microperforated muffler show that they are in good agreement with the theoretical results.
