Ultra-sensitive short-term frequency and phase stability measurement

Project Descriptiom

New technologies used in time and frequency applications call for ultra-sensitive short-term frequency and phase stability measurements of low-noise frequency sources, frequency conversion systems (such as dividers, multipliers, synthesizers), and time and frequency transfer elements (such as distribution amplifiers, signal buffers and other active components). In addition, since the measurement of short-term frequency and phase stability is an integral part of time and frequency metrology, appropriate attention should be paid to it by NMIs. The proposed project is intended to stimulate the improvements in calibration and measurement capability, to ensure consistent treatment of the issue among NMIs, and to provide a permanent platform for the exchange of results, ideas and experiences in this field.

The goals of the project are:

• to make inventory of the methods and references for the ultra-sensitive short-term frequency and phase stability (phase noise) measuremens used in NMIs
• to assess consistency, traceability and uncertainty of the measurements by making comparisons of the methods, reference frequency sources and measurement system elements
• to elaborate generic CMC specifications and calibration procedures for practical use in calibration laboratories
• to make use of possible transportation of measurement elements for the investigation of local impacts (specific spurious signals, interconnection, grounding, enviromental effects) on the uncertainty budget

Final Report 2005-04-05

2002

• Inventory of calibration/measurement capability in frequency/phase stability measurement [1] (participating IEN, PTB, ROA, SIQ, IREE)
• Working visit to IREE from IEN (one week)
• Comparison of dual-mixer time-difference multipliers (DMTDM): TSC5110A, IEN laboratory design, IREE laboratory design – version 1 (participating IEN, ROA, IREE) [2]

2003

• Working visit to IREE from SYRTE (one week)
• Optimization of the IREE DMTDM frequency-stability measurement system [3] (participating SYRTE and IREE)
• Comparison of ultra-stable 5 MHz BVA oscillators, one of SYRTE, two of IREE (participating SYRTE and IREE)

2004

• Working visits to IREE from SYRTE (one week) and ROA (one week)
• Comparison of ultra-stable 5 MHz BVA oscillators, one of ROA, two of IREE (participating ROA and IREE)
• Application of DMTDM in time delay measurement [4], [5] (participating SYRTE and IREE)
   

Conclusions
The most valuable result obtained within the project is the successful optimization of the IREE DMTDM system which at 5 MHz (15 Hz cutoff) provides the background time stability of 3.5 fs, at the basic sampling interval ?₀ = 0.2 s, with the flicker PM floor ? 2 fs (in terms of time deviation TDEV). The corresponding background frequency stability is 7x10^-15 at 1 s and 8x10^-16 at 10 s in terms of Allan deviation [3]. This noise performance, which to our knowledge is the best reported so far, has been achieved thanks to collaboration between IREE and SYRTE.

Perhaps it should be noted that the above result may also be the answer to a question that may arise about whether a project of this kind with no funds has any sense. In other words, one might think that the same result could well have been obtained without the project. Hardly so. At least in this specific case. The merit of the project is that it makes the collaboration easier. Particularly in the initial stage before our common work took a more concrete form, we had a need for a framework of some kind to start the collaboration and that is exactly what the project provided for us.

References