标题： 噪声$N$-端口的表示 显示英文标题

标题： Representations of Noisy $N$-Ports

摘要： 关于噪声线性双端口的表示已有大量论述。 在这里我们提出了一种关于噪声$N$-端口的理论。 我们展示了在一般情况下存在$(2N)!/(N!)^2$种等效表示，并给出了它们之间的变换关系。 我们还讨论了某些变换在特殊情况下不可能的情况，以及如何测量$N$-端口的噪声特性。 这项工作受到REACH实验的推动，该实验旨在观测全球21厘米信号，而为了可靠校准，精确建模噪声至关重要。 显示英文摘要

摘要： Much has been written about the representation of noisy linear 2-ports. Here we present a theory of noisy $N$-ports. We show how in the general case there are $(2N)!/(N!)^2$ equivalent representations and give the transformations relating them. We also discuss singular cases in which some of the transformations are not possible as well as how to measure the noise properties of an $N$-port. This work is motivated by the REACH experiment to observe the global 21 cm signal for which modelling noise with exquisite precision is essential for a reliable calibration.