Introduction to Symmetricom’s
QUANTUM™ Chip Scale Atomic Clock
SA.45s CSAC
Presented to Institute of Navigation
January 2012
Confidential © Copyright 2011
Agenda
• What is the CSAC?
• The Questions Everybody Asks
• How Does It Work?
• Example Applications
• Product-Specific Information
Confidential © Copyright 2011
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The QUANTUM™ Chip Scale Atomic Clock
The QUANTUM™ SA.45s Chip Scale Atomic Clock
brings the accuracy and stability of an atomic clock
to portable applications for the first time.
– ±5.0E-11 accuracy at shipment
– <3.0E-10/month aging rate
– 120 mW Power Consumption
– Only 16 cc in Volume
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History of the CSAC as a DARPA Project
• Program initiated by DARPA in 2002
– Goal: 100X smaller and lower power than existing technologies.
– Enabling technology for handheld and autonomous sensor applications.
– Used for secure communications, GPS direct P(y) acquisition, etc.
• 1st DARPA program ever to make it to Phase-III
– Phase-I (2002-2003): Proof of concept.
– Phase-II (2003-2005): 200 mW demonstration.
– Phase-III (2005-2007): 30 mW demonstration.
– Phase-IV (2008-2010): Ruggedization.
• Symmetricom team was a technology leader in the program
– First compliant physics package
– First autonomous clock
– First build of multiple units for device-to-device comparison
– Prototypes provided to multiple system demonstrations
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Agenda
• What is the CSAC?
• The Questions Everybody Asks
• How Does It Work?
• Example Applications
• Future Directions
• Product-Specific Information
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CSAC Environmentals – Shock
+Z
-Z
XY
X
• At introduction, spec was 500g 1 ms halfsine.
• After spec validation, spec was changed to
1000 g 1 ms half-sine.
• Eventually may change to 2000 g.
• Test results published in Symmetricom
whitepaper.
g-load
g-load
g-load
X-Y shock
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X shock
Z shock
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CSAC Environmentals – Temperature &
Vibration
• Temperature
–Two versions are offered: Option 001 (-10°C to +70°C; tempco =
±5.0 x 10-10); and Option 002 (-40°C to +85°C; tempco = ±1.0 x 109).
• Vibration
–Units meet Mil-STD-810, Method 514.5, procedure 1, category 24,
minimum integrity, 7.7 grms @0.04 g/Hz, 20 Hz to 1 kHz, 15 min per
axis.
–In verification testing, all units met twice this level.
–Test results in same Symmetricom whitepaper that contains shock
data.
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1 PPS for Calibration
Mission scenario: CSAC-based instrument has access to high-quality (cesium or
GPS-steered Rb/CSAC) for 10-15 minutes prior to mission.
Example:
– CSAC cold-started with +10-9 frequency error, initial sync -50 ns. (worst-case)
Phase
50 ns initial phase sync error is steered
to < 1 ns within 1000 seconds
Confidential © Copyright 2011
Frequency
+10-9 initial frequency error is steered
out within 1000 seconds
Average frequency (1000-3000 seconds) = +2x10-13
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SA.45s CSAC Licensing
• SA.45s CSAC is not under ITAR control!!
• ECCN code = EAR99.
• Eligible for export to most end users as NLR. (No License
Required)
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Agenda
• What is the CSAC?
• The Questions Everybody Asks
• How Does It Work?
• Example Applications
• Product-Specific Information
Confidential © Copyright 2011
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Miniaturizing the Physics Package
US Patent
#7215213
• Tensioned polyimide suspension.
• Microfabricated silicon vapor cell.
• Low-power Vertical-Cavity Surface Emitting Laser (VCSEL).
• Vacuum-packaged to eliminate convection/conduction – overall
demonstrated thermal resistance of 4000° C/W.
• Entire physics package can operate on 15 mW @25° C.
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How It’s Made
• Suspensions
– Spin-on polyimide over Silicon
– Photodefine polyimide and lift-off
– Metallization on polyimide
– Backside etch to release
• Resonance Cell
– DRIE holes in silicon
– Load cesium and buffer gas
– Anodic bond windows
• Stack-up
– Bond VCSEL/Photodiode to suspensions
– Stack up and epoxy on pick-and-place machine
• Vacuum Seal
Lid
Photodiode
Upper
Suspension
Resonance Cell
Cell Spacer
Frame Spacer
Lower
Suspension
VCSEL
LCC
– Bake-out and activate getter in lid before braze
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Completed Physics Package
Physics Package in LCC Before Sealing
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The Clock is More Than Just the Physics
Package
• All electronics on single PCB
• Low-power DSP and other electronics,
controlled by power-efficient proprietary
algorithms
• Double-layer magnetic shield
• Hermetically sealed
Lid
Top
Shield
Bias Coil
Physics
Package
PCB
Lower
Shield
Baseplate
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Symmetricom Atomic Clock Comparison
Atomic Oscillators
Dimensions (cm)
Volume
Power at 25° C
ADEV at 1 sec.
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X72 Precision
Rubidium Oscillator
XPRO HighPerformance
Rubidium Oscillator
SA.35m Miniature
Atomic Clock
Chip-Scale Atomic
Clock ("CSAC")
8.9 x 7.6 x 1.8
122 cm³
10 W
<3E-11
12.7 x 9.2 x 3.9
456 cm³
13 W
<1E-11
5.1 x 5.1 x 1.8
47 cm³
5W
<3E-11
4.1 x 3.3 x 1.0
16 cm³
120 mW
<3E-10
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Agenda
• What is the CSAC?
• The Questions Everybody Asks
• How Does It Work?
• Example Applications
• Product-Specific Information
Confidential © Copyright 2011
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What Application Challenges are CSAC
Customers Trying to Address?
• Applications which benefit
from CSAC
– Require precise time for synchronization
without direct connection
– Require ability to hold precise time even
in absence of GPS
– Need to minimize size, weight, and
power (SWaP)
• Examples include:
– Portable “man-pack” equipment for
the military
– Distributed geophysical sensors,
underground or underwater
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Geophysical Sensors – Marine
• Acoustic pulse hits and penetrates ocean floor.
• Sound travels thru different materials at different speeds.
• Sensors time-stamp when pulse is received.
• Post-processing of sensor data shows likely places to drill for oil.
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Today Most Marine Geophysical Sensors
Use OCXO’s as Clocks!
Critical Parameter
Why
OCXO
CSAC
Battery Lifetime
Key determinant of how long sensor can stay
underwater.
~1 W to 3 W
115 mW
Tempco
Sensor calibrated on boat deck; then goes
into very cold water.
±1.0E-8
±5.0E-10
Aging
Produces an error that varies as square of
time underwater.
<3.0E-8 per
month
<3.0E-10 per
month
Cost
Underwater nets ~2000 sensors and growing!
Less expensive
More expensive
SA.45s CSAC can often be selected on economics alone (battery
savings); but tempco and aging advantages are also important,
especially in longer-term deployments.
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CSAC Ultralow-Power Mode
• Only operate physics periodically to recalibrate TCXO
• TCXO short-term stability  CSAC long-term drift
• Average power consumption < 30 mW
– < 20 mW in TCXO-only mode
– < 140 mW during physics warmup ( 2 minutes)
– < 120 mW during full operation interval
• Example:
– 1-hour period
– 55 minutes TCXO-only
– 2-minute warm-up
– 3-minute calibration
• Average power < 30 mW
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IED Dismounted (Backpack) Jammers
• Problem:
– Need to jam wireless signals used to detonate
Improvised Explosive Devices (IEDs)
– First jammers were vehicle-mounted, but ~70%
of all patrols in Afghanistan are on foot.
– Dismounted jammers must be synchronized to
allow friendly communications, while blocking
detonation signals.
• Solution:
– CSAC precision enables synchronization, while its
low power consumption reduces the amount of
batteries needed to power the jammer.
– Small size ideal for man-pack equipment.
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Today Most Dismounted Programs Use OCXO’s!
Critical Parameter
Why
OCXO
SA.45s CSAC
Batteries determine mission life; but
battery weight must be minimized.
~1 W to 3 W
Size
Space at a premium in backpack.
Various sizes;
most much
16 cc
larger than CSAC.
Tempco
Extreme temp swings in desert
climates.
±1.0E-8
Aging
Critical to maintain time during GPS
outages; enable sync for “blue force
comms”
<3.0E-8 per
month
Cost
Fielded in tens of thousands
Less expensive
Power Consumption
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125 mW
±1.0E-9
<3.0E-10 per
month
More
expensive
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Dismounted (Backpack) Military Radios
• Today Use TCXO’s, OCXO’s
• Sometimes too much drift for GPSdenied scenarios.
• Problem will get worse with
new, higher-bandwidth waveforms.
• Excellent future application for
SA.45s CSAC as these new
waveforms get rolled out
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Tactical UAV’s
• Payloads are always
stretched on Size, Weight,
and Power (“SWaP”).
• SA.45s CSAC helps in all
three areas! (16 cc, 35 g, 125
mW)
• The CSAC also provides
excellent holdover
performance in GPS-denied
environments.
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Enhanced Military GPS Receiver
• Greatly improved TTSF.
• Holdover of ~ 24 hours with rapid
reacquisition of GPS signal.
• Improved jamming immunity.
• Possibility of lower-power operation.
• Operate with 3 satellites in view rather than
4 (only 2 satellites if altitude not needed).
Confidential © Copyright 2011
Image © Rockwell Collins, Inc.
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Enhanced Military GPS Receiver
GBGRAM+SA.45s 1PPS TIME ERROR
Time error must be < 200 ns for rapid GPS acquisition.
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Agenda
• What is the CSAC?
• The Questions Everybody Asks
• How Does It Work?
• Example Applications
• Future Directions
• Product-Specific Information
Confidential © Copyright 2011
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Developer’s Kit Evaluation Board
Analog Tuning
Input
BITE
10 MHz Output
1 PPS Output
1 PPS Input
Replaceable Fuse
5 VDC Power Input
Power Switch
3.3 VDC
RS-232 on
PC (Standard DB-9)
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Lock
Indicator
Power-On
Indicator
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CSAC Developer’s Kit -- Details
Order Symmetricom P/N 990-00123-000
• Kit contains:
–Evaluation board with socket for CSAC.
–Mounting hardware to hold evaluation board.
–Wall socket power supply to provide power to evaluation board.
–RS-232 cable to connect PC to evaluation board.
–CD-ROM with User’s Guide, sample software to control the CSAC.
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Product Information
• The SA.45s CSAC is available in
two versions:
– Option 001 (090-00218-001) is aimed at
geophysical sensors and other commercial
applications.
• -10° C to +70° C operating temperature, <120 mW
– Option 002 (090-00218-002) is aimed at
military applications.
• -40° C to +85° C operating temperature, <125 mW
• Output is 10 MHz square wave;
frequency customization is possible
for high-volume applications.
• Contact your Symmetricom representative /
distributor for pricing.
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Comparing Opt 001 and Opt 002
Q: If opt 002 has a wider temperature range than opt 001, why
isn’t it priced higher?
A: Because there are a number of other areas where opt 001 has
better specs.
Spec
Opt 001
Opt 002
Steady-State Power
Consumption
<120 mW
<125 mW
TempCo
±5 x 10-10
±1 x 10-9
ADEV (Tau = 1000 s)
5 x 10-12
7 x 10-12
Warm-up time
<130 s
<180 s
Predicted MTBF
>100,000 hrs.
>50,000 hrs.
Confidential © Copyright 2011
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Thank You
Steve Fossi
Director of New Business Development,
Government and Enterprise Business Unit
sfossi@symmetricom.com
707-636-1810
Symmetricom, Inc.
2300 Orchard Parkway
San Jose, CA 95131-1017
Tel: +1 408-428-7907
Fax: +1 408-428-6960
Confidential © Copyright 2011
www.symmetricom.com
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