Evaluation on dependence of Josephson junction generation linewidth from its geometrical dimensions and critical current

Abstract

Background. One of the most important characteristics of generators based on Josephson junctions is the power spectral density of phase noise. A number of theoretical and experimental studies showed the spectral shape of generation line is Lorentzian and its width is tens or even hundreds of megahertz. Such form of generation line and its relatively large width complicate usage of Josephson junctions in high sensitivity receivers. Objective. Problem of investigation the possibility to reduce generation linewidth and increase an output power is of current interest. In this context, the aim of this work is to study the dependence of Josephson junction generation linewidth from its geometrical dimensions and critical current. Methods. This article was written by means of usage the operator calculation method and mathematical analysis to construct mathematical models and obtain graphical dependences. Results. Studies showed the generation linewidth decreases with an increase of Josephson junction width due to reduction in differential resistance of junctions. A magnification of critical current value leads to enlargement of generation linewidth since current of both normal electrons and Cooper pairs grows and this dependence is linear. Conclusions. The analytical dependence of Josephson junction generation linewidth from its geometrical dimensions and currents of normal electrons and Cooper pairs were first obtained. Comparison of obtained dependencies with experimental results described in other works confirmed an authenticity of developed mathematical models.