Simplified Three-Cornered-Hat Technique for Frequency Stability Measurements

We propose a novel technique allowing the use of the three-cornered-hat method with two devices under test (DUTs) and a time-tagging system that employs a common reference oscillator. The precision of a time-tagging system is reduced by fluctuations in the timebase, which are canceled when the relative phase between the two DUTs is measured. However, the raw time-tags in this system provide a phase comparison between the DUTs and the system timebase, allowing the use of the three-cornered hat with some dual-channel measurement instruments.

I. Introduction

High-Stability oscillators have become increasingly vital, perhaps most visibly in the global positioning system (GPS) [1], but also for such applications as telecommunications [2], astronomy [3]–[6], and radar [7], [8]. The characterization of these oscillators is vital, but doing so requires comparison with oscillators of similar stability [9]—a requirement that becomes far less onerous if the number of comparisons can be reduced.