基于级连网络的低温放大器设计方法

Design of a cryogenic amplifier with a cascaded network

为了获得低温放大电路最佳的驻波比和噪声温度,运用级联二端口网络概念,通过矩阵变换方法,给出电压驻波比、增益和噪声系数的显式公式。为分析晶体管源极电感性网络对最佳噪声设计的影响,计算了最佳噪声信源阻抗的校正公式,用于选择合适的源极匹配网络。用上述方法设计的码分多址(CDMA)频段低温微带混合型放大器,低温(77K)实际测量得输入驻波比1.3,输出驻波比1.7,增益大于18dB,等效噪声温度不大于30K,与设计相符,证明提出的优化函数和改进的噪声模型是准确的。

A cascaded 2-port network matrix method was used to optimize the voltage standing wave ratio (VSWR) and the noise in a cryogenic RF amplifier. The S matrix transform of the transistor circuits was used to derive analytic expressions for the gain, VSWR and noise of the preamplifier. The transistor source inductive feedback was analysed to optimize the noise matching. A semi-lumped, cryogenic amplifier for a code division multiple access (CDMA) system fabricated and measured at 77 K with VSWRi as 1.3, VSWRo as 1.7, gain greater than 18 dB, noise temperature below 30 K show the accuracy of the design method and the noise model.