THE SA.45S CHIP-SCALE ATOMIC CLOCK 2011 Stanford PNT Symposium November 18, 2011 Menlo Park, CA Robert Lutwak Symmetricom - Technology Realization Center Rlutwak@Symmetricom.com
CSAC for PNT 2001 2
Physics in REALLY small cells? J. Kitching, S. Knappe, and L. Hollberg, "Performance of small-scale frequency references," presented at IEEE International Frequency Control Symposium, New Orleans, LA, 2002. J. Kitching, S. Knappe, and L. Hollberg, "Miniature vaporcell atomic-frequency references," Applied Physics Letters, vol. 81, pp. 553-555, 2002. 3
DARPA MTO CSAC Program Target Specifications Device Volume: < 1cm 3 Total Power Consumption: < 30 mw Stability: Multiple Competitive Contracts National Institute of Standards and Technology (NIST)/U. of Colorado Symmetricom/Draper/Sandia Teledyne Scientific/Rockwell Collins/Agilent Honeywell Sarnoff/Princeton/Frequency Electronics 4
The CSAC Challenge CSAC Lower Power & Better Performance 5
Navigation Applications Enhanced GPS Receivers Navigation with <4 Satellites Rapid P(y) code acquisition Spoof detection Timing holdover in GPS-denied environments Integrated Inertial Navigation Randy Rollo (SPAWAR) Navigation nugget Combine GPS, inertial nav, CSAC in manpack navigator Underwater GPS-like navigation Jeff Holland (NAVSEA Keyport) Acoustic timing beacons Ad-hoc navigation systems Self-assembling networks of first responders/dod operations 6
Other Applications Secure Communications Time-Sequence Code Acquisition in GPS-denied environments Frequency-hopping radios Datalogging Time-tagging Synthesized aperture arrays of sensors (seismology) Traingulation of signals Underwater timing applications Data-logging Automobile collision avoidance systems Telecom/Enterprise GPS timing holdover Clean-up timing source for PTP Time/Frequency in high vibration environments 7
A bit of History Era Activity Result Reporting 2001-2003 DARPA CSAC Phase-I Basic physics MEMS Components PTTI 2002 PTTI 2003 2004 DARPA CSAC Phase-II 10 mw Physics Package PTTI 2004 2005 DARPA CSAC Phase-II Autonomous CSAC PTTI 2005 2006-2007 DARPA CSAC Phase-III 2008-2010 DARPA CSAC Phase-IV Build of 10X prototypes 30 mw 1 cm 3 demo Ruggedization and environmental testing PTTI 2007 2008-2011 Symmetricom Productization SA.45s 1/18/2011 Product Announcement 8
The 10 mw Physics Package 9
Ditch the cavity Cyr & Tetu 1993 10
RF vs. CPT Requires Resonant Cavity High-Bandwidth VCSEL is Enabling Technology 11
The 10 mw Physics Package Tensioned polyimide suspension Microfabricated Silicon vapor cell Low-power Vertical-Cavity Surface Emitting Laser (VCSEL) Vacuum-packaged to eliminate convection/conduction Overall Thermal Resistance 5000 C/W US Patent #7215213 M. Mescher, et. Al., "An Ultra-Low-Power Physics Package for a Chip-Scale Atomic Clock," Proceedings of the 13th International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers '05), Seoul, Korea, June 5-9, 2005, pp. 311-316. 12
Polyimide Suspension Polyimide suspension VCSEL and Thermistor on Polyimide suspension Photos courtesy of Draper Laboratory 13
SA.45s Physics Package Cover Photodiode Upper Suspension Resonance Cell Cell Spacer Frame Spacer Lower Suspension VCSEL LCC 14
Physics Package Performance PPIII CPT Resonance Resonance Q = 5x10 7 Stability vs. Time 15
Production Statistics: Physics Package Power 16
SA.45s CSAC 17
Control System Laser Servo - Lock laser wavelength to optical absorption resonance via DC Bias Temperature Servo - Optimize optical power via temperature Clock Servo Lock local oscillator to CPT resonance Power Servo - Optimize CPT signal amplitude via µwave power 18
SA.45s CSAC Block Diagram 2 1 10 24 1 5 6 1 1 1 2 11 20 18 Microwave System: 50 mw Control System: 40 mw Physics: 10 mw Regulators & Passives: 15 mw 1 1 7 1 Total: 115 mw 19
SA.45s CSAC Lid Top Shield C Field Coil Physics Package PCB Lower Shield Baseplate 20
SA.45s Performance 21
Short-term Stability 22
Production Statistics: 1-second Stability 23
Production Statistics: 10-second Stability 24
Timing Error 25
Medium- to Long-Term Stability SN 1008CS00066 Now on ISS 26
Impact of Drift on Timing Error 27
REALLY Long-term Stability SN 084 Early functional prototype 28
Typical Temperature Sensitivity 29
Production Statistics: Temperature Sensitivity 30
Production Statistics: Power Consumption 31
Other interesting measurements 32
1 Pulse-per-Second System CSAC-dominated regime σ y (τ) 10-10 / τ 1/2 GPS-dominated regime σ y (τ) 10-8 / τ Synchronization Resolution +/- 50 ns Initial synchronization +/- 50 ns Internal 1 PPS measurement system Resolution 400 ps (better than CSAC for τ > 10 s) Self-calibration for mission initialization Discipline to GPS as holdover oscillator Discipline to GPS Self-calibration to reference 1 PPS Initial phase and frequency error steered away within 1000 seconds 33
Performance under Vibration 5X Production SA.45s CSACs tested to Mil-STD-810 Fig. 514.6E-1, 7.7 grms and 15.4 grms All 5X Units hold lock up to 15.4 grms Most units meet static ADEV spec in most axes up to 7.7 grms! 34
Exposure to Ionizing Radiation Frequency Shift 2.5x10-11 /krad 2X Production SA.45s CSACs were exposed to Total Ionizing Dose (TID) Gamma radiation testing Both units failed between 11 krad and 12 krad TID due to same op-amp (not Physics!) Minimal additional mu-metal shielding should permit LEO orbit applications at 50-100 krad TID 35
Status and Future History SA.45s CSAC is available now $1500 list price Lead times are still a little long (6-8 weeks) Manufacturing Technology (ManTech) program underway Funded by USArmy/OSD/GPS-W Objective: $100 sell price, Threshold: $300 sell price Tactical-Grade Atomic Clock (TGAC) Program Funded by Office of Naval Research Objective is smaller, lower-power, improved performance Integrated Micro-Primary Atomic Clock (IMPACT) Program Funded by DARPA MTO Objective is CSAC with 1000X improvement in drift, retrace, and temperature sensitivity 36
Acknowledgements CSAC Development Team: Symmetricom: A. Rashed, P. Vlitas, J. Deng, D. Emmons, T. Gebrewold, and R.M. Garvey Draper Laboratory: M. Varghese, G. Tepolt, J. Leblanc, and M. Mescher Sandia National Laboratories: G.M.Peake, K.M. Geib, and D.K. Serkland Symmetricom Productization Team: Design and Process Engineering: M. Silveira, D. Taylor, S. Chang, M. Juppe, J. McCartney, E. Saw, N. Dao, E. Arena, R. Dumont, M. Jiang, M. Stanczyk, L. Zanca, J. Malcolmson, and J. Dansereau Manufacturing Engineering and Operations: M-J. Bennett, S. Wilson, R. Dumont, S. Fox, E. Arena, T. Iovanella, J. McGuire, and M. Duval 37
Robert Lutwak RLutwak@Symmetricom.com and the rest of the CSAC Team. Symmetricom, Inc. 2300 Orchard Parkway San Jose, CA 95131 1017 Tel: +1 408 428 7907 Fax: +1 408 428 6960 www.symmetricom.com 38