Frequency Reference Stability and Coherence Loss in Radio Astronomy Interferometers Application to the SKA

TL;DR

This paper analyzes how frequency reference stability affects coherence loss in radio interferometers like the SKA, linking Allan deviation to coherence degradation and discussing practical limitations.

Contribution

It provides a detailed analysis of the relationship between frequency reference instability and coherence loss in radio interferometers, with practical considerations for the SKA.

Findings

Coherence loss can be quantified from Allan deviation measurements.

Practical limitations impact the stability requirements for the SKA.

The analysis guides the design of stable frequency references for radio astronomy.

Abstract

The requirements on the stability of the frequency reference in the Square Kilometre Array (SKA), as a radio astronomy interferometer, are given in terms of maximum accepted degree of coherence loss caused by the instability of the frequency reference. In this paper we analyse the relationship between the characterisation of the instability of the frequency reference in the radio astronomy array and the coherence loss. The calculation of the coherence loss from the instability characterisation given by the Allan deviation is reviewed. Some practical aspects and limitations are analysed.