在分析超声换能器阻抗特性和电路匹配的基础上,对传统纯电感电容匹配电路模型进行电路仿真和阻抗分析,证明该模型在谐振频率附近有大范围的电抗变化,存在电路不稳定和电阻调节精度低的问题;提出"电感-变压器"阻抗匹配模型,通...在分析超声换能器阻抗特性和电路匹配的基础上,对传统纯电感电容匹配电路模型进行电路仿真和阻抗分析,证明该模型在谐振频率附近有大范围的电抗变化,存在电路不稳定和电阻调节精度低的问题;提出"电感-变压器"阻抗匹配模型,通过电感和变压器分别调节换能器电阻和电抗,实现电路的精确匹配,以提高超声换能器阻抗匹配的精度和稳定性,并给出了理想的匹配条件和匹配参数。利用匝数可调的变压器和电感制作了超声换能器的匹配电路,对20.8 k Hz的变幅杆换能器进行了阻抗匹配的实验测量,结果证明这种"电感-变压器"阻抗匹配模型在谐振频率附近具有较小的电抗变化范围、较低的电阻变化率和较高的电抗调节精度,在超声换能器的自动阻抗匹配中具有良好的应用前景。展开更多
低频噪声是表征半导体器件质量和可靠性的一个重要敏感参数,为了能够测量电子器件低频噪声,使用分立器件SSM-2220组成偏置电路,由ADA4898-1构成前置放大器,采用噪声匹配变压器法设计一种测量低频低噪声的放大器。实验结果表明:在频率为8...低频噪声是表征半导体器件质量和可靠性的一个重要敏感参数,为了能够测量电子器件低频噪声,使用分立器件SSM-2220组成偏置电路,由ADA4898-1构成前置放大器,采用噪声匹配变压器法设计一种测量低频低噪声的放大器。实验结果表明:在频率为80 k Hz以下,放大器输入端共模抑制比高出集成运放OP-37 228 d B,其系统的噪声系数低于前置放大器ADA-40752 0.3 d B,满足低频低噪测量放大器的设计要求。展开更多
The two development ways of turbocharger technology to solve the problem of matching performance with diesel were presented. The ways of waste valve gate turbocharger and variable geometry turbocharger can solve the p...The two development ways of turbocharger technology to solve the problem of matching performance with diesel were presented. The ways of waste valve gate turbocharger and variable geometry turbocharger can solve the problem of engine’s low speed torque and achieve lower smoke level. Especially for variable geometry turbocharger, it covers all conditions of engine. It can not only improve the low engine’s speed torque and keep the power performance at high engine speed, but also cover wide engine speed performance that keeps lower fuel consumption and exhaust gas temperature in full load and part load matching. The results of theory analysis and experiment research showed that it’s the ideal solution to solve the matching problem of diesel engines.展开更多
文摘在分析超声换能器阻抗特性和电路匹配的基础上,对传统纯电感电容匹配电路模型进行电路仿真和阻抗分析,证明该模型在谐振频率附近有大范围的电抗变化,存在电路不稳定和电阻调节精度低的问题;提出"电感-变压器"阻抗匹配模型,通过电感和变压器分别调节换能器电阻和电抗,实现电路的精确匹配,以提高超声换能器阻抗匹配的精度和稳定性,并给出了理想的匹配条件和匹配参数。利用匝数可调的变压器和电感制作了超声换能器的匹配电路,对20.8 k Hz的变幅杆换能器进行了阻抗匹配的实验测量,结果证明这种"电感-变压器"阻抗匹配模型在谐振频率附近具有较小的电抗变化范围、较低的电阻变化率和较高的电抗调节精度,在超声换能器的自动阻抗匹配中具有良好的应用前景。
文摘低频噪声是表征半导体器件质量和可靠性的一个重要敏感参数,为了能够测量电子器件低频噪声,使用分立器件SSM-2220组成偏置电路,由ADA4898-1构成前置放大器,采用噪声匹配变压器法设计一种测量低频低噪声的放大器。实验结果表明:在频率为80 k Hz以下,放大器输入端共模抑制比高出集成运放OP-37 228 d B,其系统的噪声系数低于前置放大器ADA-40752 0.3 d B,满足低频低噪测量放大器的设计要求。
文摘The two development ways of turbocharger technology to solve the problem of matching performance with diesel were presented. The ways of waste valve gate turbocharger and variable geometry turbocharger can solve the problem of engine’s low speed torque and achieve lower smoke level. Especially for variable geometry turbocharger, it covers all conditions of engine. It can not only improve the low engine’s speed torque and keep the power performance at high engine speed, but also cover wide engine speed performance that keeps lower fuel consumption and exhaust gas temperature in full load and part load matching. The results of theory analysis and experiment research showed that it’s the ideal solution to solve the matching problem of diesel engines.
