Minimizing the linewidth of the Flux-Flow Oscillator

TL;DR

This paper uses computer simulations to accurately calculate and analyze the linewidth of Flux-Flow Oscillators, confirming theoretical formulas and identifying ways to minimize linewidth through bias current and load matching.

Contribution

First direct simulation of Flux-Flow Oscillator linewidth confirming theoretical predictions and exploring methods to minimize linewidth.

Findings

Linewidth does not depend on junction length for certain parameters.

Power and linewidth can be optimized by adjusting the unbiased tail length.

Proper load matching can reduce linewidth by 1.5 times.

Abstract

For the first time the linewidth of Flux-Flow Oscillator has been calculated by direct computer simulation of the sine-Gordon equation with noise. Nearly perfect agreement of the numerical results with the formula derived in [Phys. Rev. B, {\bf 65}, 054504 (2002)] has been achieved. It has been demonstrated that for homogeneous bias current distribution the linewidth actually does not depend on the junction length for practically interesting parameters range. Depending on the length of the unbiased tail, the power may be maximized and the linewidth may be minimized in a broad range of bias currents. The linewidth can be decreased further by 1.5 times by proper load matching.