Superconductor/insulator/superconductor (SIS) jun-ctions have extremely nonlinear electrical properties, which makes them ideal for a variety of applications, including heterodyne mixing and frequency multiplication. With SIS mixers, the SIS junctions normally have circular cross sections, but they can also be fabricated in the form of microstrip transmission lines, known as distributed SIS junctions (DSJs). By using a DSJ as an open-circuit stub, it is possible to create a large SIS junction with a low effective input reactance. This is beneficial for SIS frequency multipliers because their output power is proportional to the area of the junction. It is challenging, however, to simulate the behavior of DSJs because they have to be modeled as transmission lines and the model has to take into account the quasiparticle tunneling current, which is a nonlinear function of the ac voltage. In this article, we present a new nonlinear transmission line model to accurately describe the behavior of DSJs and to simulate the performance of distributed SIS frequency multipliers (DSMs). This model is compared to experimental data from a recent DSM device and good agreement is found between the dc tunneling currents and the output powers at the second harmonic. Based on this success, an improved DSM design is proposed that has a higher output power and a higher conversion efficiency than previous designs.

中文翻译：

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用于模拟分布式 SIS 倍频器的非线性传输线模型

超导体/绝缘体/超导体 (SIS) 结具有极其非线性的电气特性，这使得它们非常适合各种应用，包括外差混频和倍频。对于 SIS 混频器，SIS 结通常具有圆形横截面，但它们也可以制成微带传输线的形式，称为分布式 SIS 结 (DSJ)。通过使用 DSJ 作为开路短截线，可以创建具有低有效输入电抗的大型 SIS 结。这对 SIS 倍频器有利，因为它们的输出功率与结的面积成正比。然而，模拟 DSJ 的行为具有挑战性，因为它们必须被建模为传输线，并且该模型必须考虑准粒子隧道电流，这是交流电压的非线性函数。在本文中，我们提出了一种新的非线性传输线模型，以准确描述 DSJ 的行为并模拟分布式 SIS 倍频器 (DSM) 的性能。将该模型与最近的 DSM 设备的实验数据进行比较，发现直流隧道电流和二次谐波输出功率之间具有良好的一致性。基于这一成功，提出了一种改进的 DSM 设计，它比以前的设计具有更高的输出功率和更高的转换效率。将该模型与最近的 DSM 设备的实验数据进行比较，发现直流隧道电流和二次谐波输出功率之间具有良好的一致性。基于这一成功，提出了一种改进的 DSM 设计，它比以前的设计具有更高的输出功率和更高的转换效率。将该模型与最近的 DSM 设备的实验数据进行比较，发现直流隧道电流和二次谐波输出功率之间具有良好的一致性。基于这一成功，提出了一种改进的 DSM 设计，它比以前的设计具有更高的输出功率和更高的转换效率。