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在测量低噪声器件的有效噪声温度和设计低噪声天线时,传输线的噪声温度往往是不可忽略的。对于等温传输线,其噪声温度的计算式是众所周知的,卽 T=(1- 1/L)T_0 (1) 式中:T——由于传输线的损耗所引起的噪声温度(折算到其输出端); T_0——传输线所处的环境温度; L——传输线的总损耗系数,卽传输线在匹配情况下输入功率与输出功率之比,是大于一的数。
When measuring the effective noise temperature of low noise devices and designing low noise antennas, the noise temperature of the transmission line is often not negligible. For isothermal transmission lines, the calculation of the noise temperature is well known, 卽 T = (1- 1 / L) T_0 (1) where: T - the noise temperature due to transmission line losses (converted to its output) ; T_0-- ambient temperature at which the transmission line is located; L-- total loss factor of the transmission line, 卽 the ratio of input power to output power of the transmission line under a matching condition, which is greater than one.