A Small Dual Mixer Time Difference (DMTD) Clock Measuring System

This paper describes a small and relatively simple Dual Mixer Time Difference (DMTD) clock measuring system (see Figure 1). A DMTD system is a well-established way to make high resolution phase measurements on precision frequency sources. This system is intended mainly for experimental purposes, but can be used to make low-noise measurements on up to three clocks versus a reference at the same nominal frequency in the range of 1-20 MHz. The system has a resolution of 20 femtoseconds for a 10 Hz beat frequency at an RF frequency of 10 MHz as shown in Figure 2. It has achieved a coherent noise floor below 1x10 -13 at 1 second without phase averaging or cross-correlation, as shown in Figure 3, and well below that with cross-correlation. The design and implementation of the system hardware is described in detail. See Appendix I for a table of specifications for the Small DMTD Clock Measuring System. Figure 1. The Small DMTD System

[1]  R. Barillet,et al.  Optimization of dual-mixer time-difference multiplier , 2004 .

[2]  Keir Christian Lauritzen.  Correlation of Signals, Noise, and Harmonics in Parallel Analog-to-Digital Converter Arrays , 2009 .

[3]  Salvador H. Talisa,et al.  Phase Noise Model for an Array of Combined Sources Using Direct Digital Synthesis (DDS) , 2008 .

[4]  P. Tavella,et al.  Tracking nonstationarities in clock noises using the dynamic allan variance , 2005, Proceedings of the 2005 IEEE International Frequency Control Symposium and Exposition, 2005..

[5]  R. L. Sydnor,et al.  Zero-Crossing Detector with Sub-Microsecond Jitter and Crosstalk , 1990 .

[6]  C. A. Greenhall.  Frequency stability review , 1987 .

[7]  Oliver Collins,et al.  The design of low jitter hard limiters , 1996, IEEE Trans. Commun..

[8]  Thomas M. Comberiate.  Phase noise and spur reduction in an array of direct digital synthesizers , 2010 .

[9]  S. R. Stein,et al.  Software for Two Automated Time Measurement Systems , 1984 .

[10]  Albert Kirk,et al.  A multichannel dual-mixer stability analyzer: progress report , 2001 .

[11]  D. Howe,et al.  Performance of an Automated High Accuracy Phase Measurement System , 1982 .

[12]  S.R. Stein,et al.  The allan variance – challenges and opportunities , 2009, 2009 IEEE International Frequency Control Symposium Joint with the 22nd European Frequency and Time forum.

[13]  Salvador H. Talisa,et al.  Spur Correlation in an Array of Direct Digital Synthesizers , 2010 .

[14]  Martin Peckerar,et al.  Impact of Decorrelation Techniques on Sampling Noise in Radio-Frequency Applications , 2010, IEEE Transactions on Instrumentation and Measurement.

[15]  W. F. Walls.  Cross-correlation phase noise measurements , 1992, Proceedings of the 1992 IEEE Frequency Control Symposium.

[16]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[17]  David A. Howe,et al.  Properties of Signal Sources and Measurement Methods , 1981 .

[18]  Jingye Cai,et al.  A novel DDS array structure with low phase noise and spurs , 2011, 2011 IEEE 13th International Conference on Communication Technology.

[19]  D. W. Allan,et al.  Picosecond Time Difference Measurement System , 1975 .

[20]  G. Brida,et al.  Comparison of high-precision frequency-stability measurement systems , 2003, IEEE International Frequency Control Symposium and PDA Exhibition Jointly with the 17th European Frequency and Time Forum, 2003. Proceedings of the 2003.

[21]  C. A. Greenhall,et al.  A Multi-Channel Stability Analyzer for Frequency Standards in the Deep Space Network , 2006 .

[22]  C. A. Greenhall.  Digital Signal Processing in the Radio Science Stability Analyzer , 1995 .